Final Programme & Abstract Book
7th Symposium on the Role of the Vestibular Organs in Space Exploration
7 – 9 June 2006
European Space Research and Technology Centre ( ESTEC) Noordwijk, The Netherlands
Scientific committee:
C. Oman (Chair) - USA A. Clarke - Germany J. McIntyre – France F. Wuyts – Belgium F.O. Black L.R. Harris - Canada I.B. Kozlovskaya - Russia I.S Curthoys - Australia A. Berthoz - France J.B. Clark - USA J.-L. Thonnard - Belgium J. Bos - Netherlands W. Bles - Netherlands G. Clement - France
Local organising committee:
P. Sundblad (Chair) - Swedens C. Oman (for the local org. committeee) - USA E. Horn - Germany M. Heppener - The Netherlands L.R. Young - USA W.H. Paloski – USA F.O. Black - USA
Secretariat:
ESA Conference Bureau P.O. Box 299 2200 AG Noordwijk The Netherlands
Ph: +31 71 565 5005 F : +31 71 5655658 E-mail: [email protected] Final Programme / Table of Contents
Wednesday 7 June
08.00 Registration
09.00 Welcome
Session 1 Vestibulo-Ocular
Chair: Clement, G; Clarke, A.
09.40 Head Vertical (Z-Axis) Acceleration Alters Roll, Pitch and Yaw Orientation of the Eyes in the Rabbit ...... 1 Cohen, ,1; Maruta, J2; Simpson, J2; Raphan, T3 1Mount Sinai School of Medicine, UNITED STATES; 2New York University School of Medicine, UNITED STATES; 3Brooklyn College of the City University of New York, UNITED STATES
10.00 ETD Eye Tracking Device on ISS...... 2 Hofmann, P1; Schmolke, J1; Hoffmann, H2; Bauer, H3; Clarke, A4; Drüen, K4 1Kayser-Threde GmbH, GERMANY; 2DLR e.V., GERMANY; 3ESTEC, NETHERLANDS; 4Universitätsklinikum Benjamin Franklin, GERMANY
10.20 The Collinearity of Listing’s Plane and the Vestibulo-Oculomotor Reflex in Microgravity ...... 3 Clarke, A1; Haslwanter, T2 1Charité Universitätsmedizin Berlin, GERMANY; 2Upper Austrian Research Center, AUSTRIA
10.40 Modification of Eccentric Gaze-Holding ...... 4 Somers, J1; Reschke, M2 1Wyle Laboratories, UNITED STATES; 2NASA Johnson Space Center, UNITED STATES
11.00 coffee break
11.20 Modification of Eye Movements and Motion Perception during Off-Vertical Axis Rotation ...... 5 Wood, S1; Reschke, M1; Denise, P2; Clément, G3 1NASA JSC, UNITED STATES; 2Faculté de Médecine de Caen, FRANCE; 3CNRS, FRANCE
11.40 Retention of Vestibular Habituation to Repeated Velocity Steps in Humans ...... 6 Clément, G1; Courjon, J2; Tilikete, C2 1CNRS, FRANCE; 2INSERM U534 Bron, FRANCE
12.00 Static and Dynamic Vestibulo-ocular Reactions after Prolonged Microgravity ...... 7 Kornilova, L1; Alekhina, M2; Temnikova, V2; Yakushev, A3 1RF SSC-IBMP, R.Ac.Sc., Moscow, Russia, RUSSIAN FEDERATION; 2RF SSC-IBMP, R.Ac.Sc., RUSSIAN FEDERATION; 3Lomonosov's Moscow State University, RUSSIAN FEDERATION
12.20 A Comparison of Gravity-Dependent Adaptation of The Roll, Pitch and Yaw Angular Vor (Avor) ...... 8 Yakushin, S1; Storozh, O1; Xiang, Y2; Raphan, T2; Cohen, B1 1Mount Sinai School of Medicine, UNITED STATES; 2Brooklyn College, CUNY, UNITED STATES
12.40 Effects of Water Immersion on The Gaze Fixation Reaction in Rhesus Monkeys ...... 9 Badakva, A; Miller, N; Eron, J RF SRC – Institute of Biomedical Problems RAS, RUSSIAN FEDERATION
13.00 Lunch Session 2 Clinical Assessment
Chair: Sundblad, P; Wuyts, F
14.00 Testing Otolith Function: 500Hz Bone Conducted Vibration Selectively Activates Irregular Otolithic Neurons and Causes An Eye Movement Response in Humans ...... 10 Curthoys, I1; Kim, J2; Burgess, A2; Camp, A2; McPhedran, S2; Attard, M2; McGarvie, L3; Halmagyi, G3; Iwasaki, S4 1University of Sydney, AUSTRALIA; 2School of Psychology, University of Sydney, AUSTRALIA; 3Royal Prince Alfred Hospital, Sydney, NSW, AUSTRALIA; 4Department of Otolaryngology, University of Tokyo, Tokyo, JAPAN
14.20 Measurement of Otolith Ocular Counterroll without Head or Body Restraints ...... 12 Brütting, M Research Establishment for Applied Science (FGAN), GERMANY
14.40 Otholith Function Testing: Sinusoidal Lateral Displacement during 400 Deg/S Rotations ...... 13 Wuyts, F; Vanspauwen, R; Jansen, E; Van de Heyning, P University of Antwerp, BELGIUM
15.00 The Effect of Angular Velocity on Brain Cognitive Processing: An ERP Study ...... 14 Wang, L; Zhang, D; Guo, J; Cao, Y; Zhao, Q; Tong, F; Niu, D Institute of Space-Medico Engineering, CHINA
15.20 Coffee break
Session 3 Neuropysiology
Chair: Curthoys, I.S; Horn, E
15.40 Effect of The Protonophore FCCP on The Glutamate Release from Rat Brain Synaptosomes under Altered Gravity Conditions ...... 15 Borisova, T; Krisanova, N Palladin Institute of Biochemistry NAS of Ukraine, UKRAINE
16.00 Exposure to Microgravity during Spaceflight and Suppression of The Transcription Factor Xtcf-4 Result in Similar Phenotypes in Tadpoles (Xenopus Laevis)...... 16 Horn, E1; El-Yamany, N2; Wedlich, D3; Kunz, M3; Gradl, D3 1University, GERMANY; 2Zoology Department, Helwan University, Cairo, EGYPT; 3Zoology Department, University of Karlsruhe, Karlsruhe, GERMANY
16.20 EEG Changes in The Hippocampus Following Bilateral Vestibular Damage ...... 17 Smith, P1; Smith, P2; Russell, N2; Horii, A3; Darlington, C2; Bilkey, D2 1University of Otago Medical School, NEW ZEALAND; 2University of Otago, NEW ZEALAND; 3University of Osaka, JAPAN
17.00 Departure by bus to Katwijk harbour
17.15 Departure for dinner cruise
21.00 Departure by Bus to Estec and various hotels Noordwijk
Thursday 8 June
Session 4 Spatial Orientation
Chair: Oman, C; McIntyre, J
09.00 Reproduction of Vestibular Stimulation Duration...... 18 Israël, I1; Capelli, A1; Leboucher, P1; Rivaud-Péchoux, S2; Gaymard, B2 1CNRS, FRANCE; 2INSERM, FRANCE
09.20 Adjustment of Body Position in Pitch and Roll...... 20 Jarchow, T Massachusetts Institute of Technology, UNITED STATES
09.40 Temporal Estimates during Post-Rotatory Sensation ...... 21 Capelli, A; Bobin, A; Israel, I LPCMV, CNRS-Renault, UMR2858, FRANCE
10.00 A Bayesian Model for Estimating Body Orientation from Vestibular and Visual Information ...... 22 MacNeilage, P; Banks, M UC Berkeley, UNITED STATES
10.20 Perceptual Centering of Body Segment Orientation ...... 24 Hanes, D Legacy Research Center, UNITED STATES
10.40 Measuring the Perceptual Upright while Manipulating Body Orientation and the Orientation of the Visual Background Relative to Gravity...... 26 Dyde, R; Jenkin, M; Harris, L York University, CANADA
11.00 Coffee break
11.20 Effect of Field of View on a Visual Reorientation Illusion: Does the levitation Illusion Depend on the View Seen or the Scene Viewed? ...... 27 Jenkin, H1; Zacher, J1; Oman, C2; Harris, L1 1York University, CANADA; 2Massachusetts Institute of Technology, UNITED STATES
11.40 Visual Cues to the Direction of the Floor: Implications for Spacecraft Design ...... 28 Harris, L1; Dyde, R1; Oman, C2; Jenkin, M1 1York University, CANADA; 2Massachusetts Institute of Technology, UNITED STATES
12.00 Spatial Memory Deficits Following Vestibular Damage: Do They Recover Over Time? ...... 29 Darlington, C1; Darlington, C2; Zheng, Y3; Goddard, M3; Smith, P3 1University of Otago Medical School, NEW ZEALAND; 2University of Otago, NEW CALEDONIA; 3University of Otago, NEW ZEALAND
12.20 Incongruent Spacecraft Module Visual Verticals Affect Spatial Task Performance ...... 30 Oman, C1; Benveniste, D1; Buckland, D1; Aoki, H1; Liu, A1; Natapoff, A1; Kozhevnikov, M2 1Massachusetts Institute of Technology, UNITED STATES; 2Rutgers University, UNITED STATES
12.40 The Effect of The Configuration, Frame of Reference, and Spatial Ability on Spatial Orientation during Virtual Three-Dimensional Navigation Train...... 31 Hirofumi Aoki, H; Charles M. Oman, C; Alan Natapoff, A; Andrew M. Liu, A Massachusetts Institute of Technology, UNITED STATES
13.00 Lunch Session 5 Spaceflight Countermeasures
Chair: Clark, J B; Kozlovskaya, I B
14.00 Head Tilt Posturography to Enhance Balance Control Assessment for Astronauts: A Case Study ...... 32 Hwang, E1; Paloski, W2 1Wyle Life Sciences, UNITED STATES; 2NASA Johnson Space Center, UNITED STATES
14.20 Functional and Performance Tests before, during, and after Long-duration Space Flight ...... 34 Hoffer, M1; Gottshall, K1; Clark, J2; Black, O3 1Naval Medical Center San Diego, UNITED STATES; 2NASA, UNITED STATES; 3Legacy Clinical Research Center, UNITED STATES
14.40 Astronaut Selection and Training to Optimize Maintenance of Spatial Orientation ...... 35 Rupert, A1; Clark, J2; Oman, C3 1Naval Aerospace Medical Research Laboratory, UNITED STATES; 2National Space Biomedical Research Institute, UNITED STATES; 3Massachusetts Institute of Technology, UNITED STATES
15.00 Spatial Disorientation during Orbiter Landing ...... 36 Moore, S1; MacDougall, H1; Clark, J2; Wuyts, F3; Lesceu, X4; Speyer, J4 1Mt Sinai School of Medicine, UNITED STATES; 2NSBRI, UNITED STATES; 3Antwerp University, BELGIUM; 4Airbus, FRANCE
15.20 Coffee break
Session 6 Balance & Locomotion
Chair: Black, F O; Thonnard, J L
15.40 Influence of Tactile Sensory Supplementation on Controlling Upright Stance during Postural Perturbations .. 37 Black, F1; Stallings, V1; Wood, S2 1Legacy Clinical Research & Technology Center, UNITED STATES; 2NASA Johnson Space Center, UNITED STATES
16.00 Effects of Vibrotactile Feedback on Manual Control Performance during Flight Tests and Laboratory Tilt Nulling Tasks ...... 38 Rupert, A1; Wood, S2 1Naval Aerospace Medical Research Laboratory, UNITED STATES; 2NASA JSC, UNITED STATES
16.20 Galvanic Vestibular Stimulation as a Model for Space Adaptation Syndrome ...... 39 MacDougall, H; Moore, S Mount Sinai School of Medicine, UNITED STATES
16.40 Adaptive Changes in Postural Equilibrium and Motion Sickness Following Repeated Exposures to Virtual Environments ...... 41 Harm, D1; Taylor, L2 1NASA Johnson Space Center, UNITED STATES; 2Wyle Laboratories, UNITED STATES
17.00 Cocktail Museum Space Expo (just outside the ESTEC premises, 5 minutes walk)
19.00 Departure by bus to the various hotels in Noordwijk
Friday 9 June
Session 7 Motion Sickness
Chair: Bos, J; Oman, C.
09.00 Chlorpheniramine and Ephedrine in Combination for Motion Sickness...... 42 Buckey, J; Alvarenga, D Dartmouth Medical School, UNITED STATES
09.20 Sustained Hypergravity to Simulate Sas: Effect 0f G-Load And Duration ...... 43 Nooij, S; Bos, J TNO Human Factors, NETHERLANDS
09.40 The Laboratory Assessment of Anti-Motion Sickness Histaminergic Drugs...... 44 Matsnev, E1; Matsnev, E2 ;Sigaleva E.E. 1Academy Sciences of Russia – State Research Center of Russia - Institute for Biomedical Problems., RUSSIAN FEDERATION; 2Institute for Biomedical Problems, RUSSIAN FEDERATION
10.00 Modeling the Role of Velocity Storage in Motion Sickness...... 45 Raphan, T1; Cohen, B2; Kaufmann, H2; Dai, M2 1City University of New York (Brooklyn College), UNITED STATES; 2Mount Sinai School of Medicine, UNITED STATES
10.20 Cancelled Stroboscopic Vision as A Treatment for Space Motion Sickness ...... 46 Reschke, M1; Somers, J2; Ford, G2; Krnavek, J2; Hwang, E2 1NASA Johnson Space Center, UNITED STATES; 2Wyle, UNITED STATES
10.40 Susceptibility to Kinetosis under Reduced Gravity – a Brief Review on Lessions Learned from Fish as Model System ...... 47 Hilbig, R1; Anken, R2 1University of Stuttgart-Hohenheim, GERMANY; 2University of Stuttgart Hohenheim, GERMANY
11.00 Coffee break
Session 8 Artificial Gravity
Chair: Paloski, W H; Young, L R
11.20 Relevance of Rotating Room Experiments to Vestibular Patient Rehabilitation and Adaptation in Rotating Space Stations ...... 48 Guedry, F1; Rupert, A2 1Pensacola FL, UNITED STATES; 2Naval Aerospace Medical Research Laboratory, UNITED STATES
11.40 Effect of Radius Versus Rotation Speed in Artificial Gravity...... 49 Holly, J Colby College, UNITED STATES
12.00 A Parametric Study of Vestibular Stimulation during Centrifugation ...... 51 Jarchow, T; Pouly, J; Young, L Massachusetts Institute of Technology, UNITED STATES
12.20 Response of Ambulatory Human Subjects to Artificial Gravity (Short Radius Centrifugation) ...... 53 Paloski, W1; Arya, M2; Newby, N2; Tucker, J1; Jarchow, T3; Young, L3 1NASA/Johnson Space Center, UNITED STATES; 2Wyle Laboratories, UNITED STATES; 3MIT Man-Vehicle Laboratory, UNITED STATES 12.40 Motor Imagery as an Adaptation Method for Head Turns on a Short-Arm Centrifuge ...... 54 Newby, N1; Mast, F2; Natapoff, A3; Paloski, W4 1Wyle Labs, UNITED STATES; 2University of Lausanne, SWITZERLAND; 3MIT, UNITED STATES; 4NASA Johnson Space Center, UNITED STATES
13.00 Lunch
Session 9 Otolith and Semicircular Canal Physiology
Chair: Curthoys, I S; Bles, W
14.00 Implications of Spatial Symmetries in Vestibular Projections for Sensorimotor Behaviors in Differing Gravitational Levels -- Review ...... 55 McCollum, G Legacy Research Center, UNITED STATES
14.20 Visualizing The Orientation of Otolith Receptor Structures using High-Resolution Xray Microtomography ..57 Curthoys, I1; Uzun, H1; Jones, A1; Bradshaw, A2; Todd, M2; Halmagyi, G2 1University of Sydney, AUSTRALIA; 2Royal Prince Alfred Hospital, AUSTRALIA
14.40 The Effect of Difference of The Cupula and Endolymph Densities on Dynamics of Cupula ...... 58 Kondrachuk, A1; Sirenko, S2; Boyle, R3 1Institute of Physics, Natl.Acad. of Sci., UKRAINE; 2Institute of Nuclear Research, Natl.Acad.of Sci., UKRAINE; 3BioVIS Technology Center and Vestibular Research Facility, Ames Research Center, NASA, UNITED STATES
15.00 Aspects of a Neuronal Regulation of Inner ear Otolith Mineralization in Fish – a Brief Review...... 60 Anken, R1; Hilbig, R2 1University of Stuttgart-Hohenheim, GERMANY; 2University of Stuttgart Hohenheim, GERMANY
15.20 Panel Discussion on the role of Vestibular research in Space Exploration- challenges and opportunities......
16.00 end
Posters
Vestibulo-Ocular
Gaze Holding as a Measure Of Vestibular After-Effects in Pilots and Gymnasts...... 61 Wetzel, E1; Hecht, H2 1Johannes Gutenberg-Universität Mainz, GERMANY; 2Johannes Gutenberg-Univerität Mainz, Department of General Experimental Psychology, GERMANY
Effects of Long Duration Flight on Organization of Horizontal and Vertical Gaze Fixation Reaction...... 62 Tomilovskaya, E1; Berger, M2; Gerstenbrand, F2; Kozlovskaya, I1 1RF State Research Center - Institute for Biomedical Problems of the Russian Academy of sciences, RUSSIAN FEDERATION; 2Innsbruck Institute of Space Neurology, AUSTRIA
Clinical Assessment
Usefulness of Current Balance Tests for Identifying Balance-Impaired Individuals...... 63 Cohen, H1; Kimball, K2; Mulavara, A3; Bloomberg, J4 1Baylor College of Medicine, UNITED STATES; 2Statistical Design and Analysis, UNITED STATES; 3National Space Biomedical Research Institute, UNITED STATES; 4NASA/ Johnson Space Center, UNITED STATES
Neuropysiology
Glutamatergic Stimulation of The Medial Vestibular Nucleus Evokes The Inhibition of Respiratory Rhythm in The Isolated Brainstem-Spinal Cord of Newborn Rat ...... 64 Glazkova, E1; Pyatin, V2; Rybakov, S2 1State Medical University, RUSSIAN FEDERATION; 2Samara State Medical University, RUSSIAN FEDERATION
Effect of Prolonged Bed Rest on the Vestibulosympathetic Reflex ...... 65 Ray, C1; Dyckman, D1; Kearney, M1; Meck, J2 1Penn State College of Medicine, UNITED STATES; 2NASA Johnson Space Center, UNITED STATES
Consequences of the Development under Modified Gravity on the Setting of the Vestibular Sensory Network in the Rat Chabbert, C; Brugeaud, A; Gaboyard, S...... 66 INSERM U583, FRANCE
A Non Destructive Miniaturized Method of Identification of metabolites in Tissue ...... 67 karavolos, p; karavolos, A Schaller Engineering/NT Systems, UNITED STATES
Spatial Orientation
Measuring and Attenuating Head-Movement Induced Oscillopsia ...... 68 Sanderson, J1; Kalsey, J1; Oman, C2; Harris, L1 1York University, CANADA; 2Massachusetts Institute of Technology, UNITED STATES
Mental Transformations of Bodies and Body-parts in Microgravity ...... 69 Grabherr, L1; Bach, S2; Indermaur, K3; Metzler, S4; Mast, F1 1University of Lausanne, SWITZERLAND; 2Memory Clinic Basel, SWITZERLAND; 3University of Fribourg, SWITZERLAND; 4University of Zurich, SWITZERLAND
The Role of Visual Background Orientation on the Perceptual Upright during Parabolic Flight ...... 70 Dyde, R; Jenkin, M; Jenkin, H; Zacher, J; Harris, L York University, CANADA
Tilt and Translation Motion Perception during Pitch Tilt with Visual Surround Translation ...... 71 O' Sullivan, B; Harm, D; Reschke, M; Wood, S NASA JSC, UNITED STATES
Sensory Disorientation in Space Habitats - a Challenge for Spacearchitects and Space Psychologists ...... 72. Jorgensen, J SpaceArch, DENMARK
Spaceflight Countermeasures
The Use of Dynamic Visual Acuity as a Functional Test of Gaze Stabilization Following Space Flight ...... 74 Peters, B1; Mulavara, A2; Brady, R3; Miller, C3; Richards, J3; Warren, L4, H5; Bloomberg, J6 1Wyle Laboratories, Inc., UNITED STATES; 2National Space Biomedical Research Institute, Baylor College of Medicine, UNITED STATES; 3Wyle Laboratories, Inc., Neuroscience Laboratory, UNITED STATES; 4Universities Space Research Association, UNITED STATES; 5Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, UNITED STATES; 6Neuroscience Laboratories, NASA-Johnson Space Center, UNITED STATES
Development of Testing Methodologies to Evaluate Postflight Locomotor Performance ...... 75 Mulavara, A1; Peters, B2; Cohen, H3; Richards , J2; Miller, C2; Brady, R2; Warren, L4; Kozlovskaya, I5; Bloomberg, J6 1National Space Biomedical Research Institute, Baylor College of Medicine, Houston, TX, UNITED STATES; 2Wyle Laboratories, Houston, TX, UNITED STATES; 3Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, BCM, Houston, TX, UNITED STATES; 4Universities Space Research Association Division of Space Life Sciences, Houston, TX, UNITED STATES; 5Institute for Biomedical Problems, Moscow, RUSSIAN FEDERATION; 6NASA-Johnson Space Center, Houston, TX, UNITED STATES
Development of a Countermeasure to Mitigate Postflight Locomotor Dysfunction ...... 77 Bloomberg, J1; Mulavara, A2; Peters, B3; Cohen, H4; Richards, J3; Miller, C3; Brady, R3; Warren, L5; Ruttley, T1; Kozlovskaya, I6 1NASA-Johnson Space Center, Houston, TX, UNITED STATES; 2National Space Biomedical Research Institute, Baylor College of Medicine, Houston, TX, UNITED STATES; 3Wyle Laboratories, Houston, TX, UNITED STATES; 4Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, BCM, Houston, TX, UNITED STATES; 5Universities Space Research Association Division of Space Life Sciences, Houston, TX, UNITED STATES; 6Institute of Biomedical Problems, Moscow, RUSSIAN FEDERATION
Development of In-Flight Countermeasures with Multimodal Effects - Muscle Strength and Balance Function...... 79 Oddsson, L1; Bloomberg, J2; Zemkova, E3; Dwyer, A4; Chow, A4; Meyer, P5; Wall, C6 1Boston University, UNITED STATES; 2NASA/Johnson Space Center, Houston, UNITED STATES; 3Faculty of Physical Education and Sports, Comenius University, Bratislava, SLOVAKIA; 4Department of Biomedical Engineering, Boston University, UNITED STATES; 5Tyco Healthcare, UNITED STATES; 6Massachusetts, Eye and Ear Infirmary/Harvard Medical School, Boston, UNITED STATES
Assessment of Postflight Locomotor Performance Utilizing a Test of Functional Mobility: Strategic and Adaptive Responses ...... 81 Warren, L1; Mulavara, A2; Peters, B3; Cohen, H4; Richards, J3; Miller, C3; Brady, R3; Ruttley, T5; Bloomberg, J5 1Universities Space Research Association, UNITED STATES; 2National Space Biomedical Research Institute, Baylor College of Medicine, UNITED STATES; 3Wyle Laboratories, UNITED STATES; 4Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine, UNITED STATES; 5Neuroscience Laboratories, NASA-Johnson Space Center, UNITED STATES
Balance & Locomotion
Relative Contributions of Strategic and Adaptive Control Mechanisms in Plastic Recalibration of Locomotion ...... 83 Richards, J1; Mulavara, A2; Ruttley, T3; Peters, B1; Warren, L4; Bloomberg, J3 1Wyle Laboratories, Inc., UNITED STATES; 2National Space Biomedical Research Institute, UNITED STATES; 3NASA Johnson Space Center, UNITED STATES; 4Universities Space Research Association, UNITED STATES
Motion Sickness
Dependence of Motion Sickness Susceptibility On the Time Constant of the Angular Vestibulo-Ocular Reflex (aVOR) Dai, M1; Raphan, T2; Cohen, B3 ...... 84 1Mount Sinai School of Medicine, UNITED STATES; 2Department of Computer and Information Science, Brooklyn College, CUNY, Brooklyn, NY, UNITED STATES; 3Department of Neurology, Mount Sinai School of Medicine, NY, UNITED STATES
Otolith and Semicircular Canal Physiology
The distribution of Otolith Polarization Vectors Based on the Curvature of Macular Surfaces in Mammals ...... 85 Kondrachuk, A1; Jaeger, R2; Haslwanter, T3 1Institute of Physics, Natl.Acad.of Sci., UKRAINE; 2Dept. of Astrophysics, University of Tuebingen, GERMANY; 3Up. Austr.Res, Dept. for Med.Inf. Linz,Austria & Inst. of Theor.Physics, ETH Zurich, SWITZERLAND
Ultrastructural and Confocal Study of Vestibular Hair Cells from the Tilted Mouse...... 87 Gaboyard-Niay, S; Price, S; Lysakowski, A University of Illinois at Chicago, UNITED STATES Other
National Space Biomedical Research Institute Education and Outreach ...... 88 Rahmati Clayton, S1; Thomson, W1; MacLeish, M2; Moreno, N1 1Baylor College of Medicine, UNITED STATES; 2Morehouse School of Medicine, UNITED STATES
HEAD VERTICAL (Z-AXIS) ACCELERATION ALTERS ROLL, PITCH AND YAW ORIENTATION OF THE EYES IN THE RABBIT Cohen, ,1; Maruta, J2; Simpson, J2; Raphan, T3 1Mount Sinai School of Medicine; 2New York University School of Medicine; 3Brooklyn College of the City University of New York
We have previously shown that orienting eye movements produced by translation while rotating (TWR) have smaller sensitivities (°/g) than those produced by static tilt and off-vertical axis rotation (OVAR). We postulated that the difference was due to the presence of the constant gravitational acceleration along the head vertical axis during TWR but not during static tilt or OVAR. During pitch tilts, which produced naso-occipital acceleration, ocular counter-pitch and vergence had sensitivities of 25°/g and 26°/g (13° each eye) and during roll tilts, which produced bitemporal acceleration, roll and yaw had sensitivities of 20°/g and 5°/g. When acceleration was applied along the naso-occipital axis during centrifugation with gravity along the head vertical axis, the sensitivities of pitch and vergence fell to 13°/g and 16°/g (8° each eye), respectively. Centripetal acceleration applied along the bitemporal axis with 1 g along the vertical axis reduced the sensitivity of roll eye movement to 16°/g. Thus, the presence of the constant acceleration of gravity reduced the sensitivities of eye rotation to naso- occipital and bitemporal linear acceleration. Applying centripetal acceleration directly along the head vertical axis reduced the sensitivities of pitch and vergence relative to naso-occipital acceleration by 6°/g and 2°/g, and roll sensitivity relative to bitemporal acceleration by 5°/g. In addition, the combination of bitemporal and vertical axis accelerations induced small degrees of ocular pitch and convergence de novo. These results support the hypothesis that acceleration along the head vertical axis has a significant role in determining the sensitivity and direction of ocular orientation.
1 ETD EYE TRACKING DEVICE ON ISS Hofmann, P1; Schmolke, J1; Hoffmann, H-U2; Bauer, H3; Clarke, A4; Drüen, K4 1Kayser-Threde GmbH; 2DLR e.V.; 3ESTEC; 4Universitätsklinikum Benjamin Franklin
On the International Space Station ISS an Eye Tracking Device "ETD" is available for scientific studies in the field of Vestibular Research. ETD measures, records and evaluates human eye movements. It provides a new tool for the medical examination and for the investigation of the human neurovestibular system. ETD was originally built for a NASA shuttle launch as a cooperative German/American project. The hardware was developed and built by Kayser-Threde, Munich and Chronos Vision, Berlin under a contract to DLR. Due to the shuttle launch delays, it was agreed between Roskosmos, NASA, ESA and DLR to launch ETD with the Russian Progress Vehicle and to operate ETD in the Russian ISS module until a later delivery to NASA. ETD was launched in January 2004 and is now in more or less continuous operation on the ISS. PI is Andrew Clarke, first scientific results of these sessions will be described during this conference in a parallel session. This paper will summarize the performance and status of the ETD hardware and software, upgrades which already have been implemented, or are planned to be incorporated. Finally an outlook will be given addressing the planning for the next increments and related development activities at Kayser-Threde.
2 THE COLLINEARITY OF LISTING’S PLANE AND THE VESTIBULO- OCULOMOTOR REFLEX IN MICROGRAVITY. Clarke, AH1; Haslwanter, T2 1Charité Universitätsmedizin Berlin; 2Upper Austrian Research Center
The results from ongoing experiments onboard the ISS will be presented. These are concerned with the gravity-dependence of the oculomotor and vestibular systems.
Under normal gravity conditions the orientation of Listing's Plane varies very little in humans. In addition, it has been demonstrated that it is near collinear with the VOR co-ordinate frame. The working hypothesis is that in microgravity – due to the absence of the otolith-mediated gravity vector - the orientation of Listing's Plane diverges from that of the VOR co-ordinate frame. The 3D-VOR coordinates are determined from measurements of eye and head movements during active head roll, pitch and yaw. Listing's plane is calculated from measurements of random saccades. 3D eye and head movements were sampled at 200 Hz using the DLR Eye Tracking Device.
Currently, experiments are being conducted onboard the ISS, with control experiments in the lab and during parabolic flight. The first results indicate that not only the orientation of the 3D-VOR, but also that of the individual's Listing's Plane is altered in microgravity to an extent greater thatn observed on Earth. This indicates that the otolith-mediated gravity vector represents a common spatial reference to the central nervous system, the loss of which may lead to a dissociation of otherwise closely coupled sensory-motor systems.
3 MODIFICATION OF ECCENTRIC GAZE-HOLDING Somers, JT1; Reschke, MF2 1Wyle Laboratories; 2NASA Johnson Space Center
BACKGROUND: Clear vision and accurate localization of objects in the environment are prerequisites for reliable performance of motor tasks. Space flight confronts the crewmember with a stimulus rearrangement that requires adaptation to function effectively with an altered spatial orientation and motor coordination. Adaptation and motor learning driven by the effects of cerebellar disorders may share some of the same demands that face our astronauts. One measure of spatial localization shared by the astronauts and those suffering from cerebellar disorders that is easily quantified, and for which a neurobiological substrate has been identified, is the control of the angle of gaze (the 'line of sight'). The disturbances of gaze control that have been documented to occur in astronauts and cosmonauts, both in-flight and postflight, can be directly related to changes in the extrinsic gravitational environment and intrinsic proprioceptive mechanisms, thus lending themselves to description by simple non-linear statistical models. Due to the necessity of developing robust normative populations against which abnormal responses can be evaluated, the basic models can be formulated using normal, non-astronaut test subjects. Subsequently, the models could be extended using centrifugation techniques to alter the gravitational and proprioceptive environment of these subjects. Further tests and extensions of the models can be made by studying abnormalities of gaze control in patients with cerebellar disease.
METHODS: A series of investigations were conducted in which a total of 33 subjects were tested to: (1) Define eccentric gaze-holding parameters in a normative population, and (2) explore the effects of linear acceleration on gaze-holding parameters. For these studies gaze holding was evaluated with the subjects seated upright (the normative values) and pitched back 90°. In a separate study the further effects of acceleration on gaze stability was examined during centrifugation (+2 Gx and +2 Gz) using a total of 23 subjects. In all of our investigations eccentric gaze holding was established by having the subjects acquire an eccentric target (circa 30° horizontal, circa 15° vertical) that was flashed for 750 msec in an otherwise dark room. Subjects were instructed to hold gaze on the remembered position of the flashed target for 20 sec. Immediately following the 20 sec period, subjects were cued to return to the remembered center position and to hold gaze there for an additional 20 sec. Following this 20 sec period the center target was briefly flashed and the subject made any corrective eye movement back to the true center position. To determine the ability to hold eccentric gaze, the data were analyzed by calculating the time constant (?c) of slow phases of 'gaze-evoked nystagmus' during the first 2 seconds of eccentric gaze holding. However, because our normative subjects sometimes showed essentially no drift (?c = ?), we found the data were well modeled by a log-normal distribution.
RESULTS: Subjects showed substantial variance of their eye drifts, which were centrifugal in more than 20 % of horizontal and upward gaze, and > 40% for down gaze. Using the ensuing estimated log- normal distributions, we were able to conclude that vertical gaze holding was worse than horizontal. We also concluded that rightward and leftward gaze holding were not different, but that upward gaze holding was worse than downward. For pitch tilts, gaze-holding ability decreased in all directions. Finally, we found that hyper-g centrifugation decreased gaze holding ability in the vertical plane.
CONCLUSIONS: The main findings of this study are as follows: (1) vertical gaze-holding is less stable than horizontal, (2) gaze-holding to upward targets is less stable than to downward targets, (3) tilt affects gaze holding, and (4) hyper-g affects gaze holding. This difference between horizontal and vertical gaze holding may be ascribed to separate components of the velocity-to-position neural integrator for eye movements, and to differences in orbital mechanics. The differences within vertical gaze holding, between upward and downward target directions may be ascribed to an inherent vertical imbalance in the vestibular system. Since whole body tilt and hyper-g effect gaze holding, it is implied that the otolith organs have direct connections to the neural integrator and further studies of astronaut gaze-holding are warranted. Our statistical method for representing the range of normal eccentric gaze stability can be readily applied to normals who maybe exposed to environments which may modify the central integrator and require monitoring, and to evaluate patients with gaze-evoked nystagmus by comparing to the above established normative criteria.
4 MODIFICATION OF EYE MOVEMENTS AND MOTION PERCEPTION DURING OFF-VERTICAL AXIS ROTATION Wood, SJ1; Reschke, MF1; Denise, P2; Clément, G3 1NASA JSC; 2Faculté de Médecine de Caen; 3CNRS
Background: constant velocity off-vertical axis rotation (ovar) imposes a continuously varying orientation of the head and body relative to gravity. The ensuing ocular reflexes include modulation of both torsional and horizontal eye movements as a function of the varying linear acceleration along the lateral plane, and modulation of vertical and vergence eye movements as a function of the varying linear acceleration along the sagittal plane. Previous studies have demonstrated that tilt and translation otolith-ocular responses, as well as motion perception, vary as a function of stimulus frequency during ovar. The purpose of this study is to examine normative ovar responses in healthy human subjects, and examine adaptive changes in astronauts following short duration space flight at low (0.125 hz) and high (0.5 hz) frequencies.
Methods: data was obtained on 24 normative subjects (14 m, 10 f) and 14 (13 m, 1f) astronaut subjects. To date, astronauts have participated in 3 preflight sessions (n=14) and on r+0/1 (n=7), r+2 (n= 13) and r+4 (n= 13) days after landing. Subjects were rotated in darkness about their longitudinal axis 20 deg off- vertical at constant rates of 45 and 180 deg/s, corresponding to 0.125 and 0.5 hz. Binocular responses were obtained with video-oculography. Perceived motion was evaluated using verbal reports and a two-axis joystick (pitch and roll tilt) mounted on top of a two-axis linear stage (anterior-posterior and medial-lateral translation). Eye responses were obtained in ten of the normative subjects with the head and trunk aligned, and then with the head turned relative to the trunk 40 deg to the right or left of center. Sinusoidal curve fits were used to derive amplitude, phase and bias of the responses over several cycles at each stimulus frequency.
Results: eye responses during 0.125 hz ovar were dominated by modulation of torsional and vertical eye position, compensatory for tilt relative to gravity. While there is a bias horizontal slow phase velocity (spv), the modulation of horizontal and vergence spv is negligible at this lower stimulus frequency. Eye responses during 0.5 hz ovar; however, are characterized by modulation of horizontal and vergence spv, compensatory for translation in the lateral and sagittal planes, respectively. Neither amplitude nor bias velocities were significantly altered by head-on-trunk position. The phases of the ocular reflexes, on the other hand, shifted towards alignment with the head. During the lower frequency ovar, subjects reported the perception of progressing along the edge of a cone. During higher frequency ovar, subjects reported the perception of progressing along the edge of an upright cylinder. In contrast to the eye movements, the phase of both perceived tilt and translation motion is not altered by stimulus frequency. Preliminary results from astronaut data suggest that the ocular responses are not substantially altered by short-duration spaceflight. However, compared to preflight averages, astronauts reported greater amplitude of both perceived tilt and translation at low and high frequency, respectively, during early post-flight testing.
Conclusions: We conclude that the neural processing to distinguish tilt and translation linear acceleration stimuli differs between eye movements and motion perception. The results from modifying head-on-trunk position are consistent with the modulation of ocular reflexes during OVAR being primarily mediated by the otoliths in response to the sinusoidally varying linear acceleration along the interaural and naso- occipital head axis. While the tilt and translation ocular reflexes appear to operate in an independent fashion, the timing of perceived tilt and translation influence each other. We conclude that the perceived motion path during linear acceleration in darkness results from a composite representation of tilt and translation inputs from both vestibular and somatosensory systems.
5 RETENTION OF VESTIBULAR HABITUATION TO REPEATED VELOCITY STEPS IN HUMANS Clément, G1; Courjon, J-H2; Tilikete, C2 1CNRS; 2INSERM U534 Bron
BACKGROUND: During the Fifth Symposium in this series held in Pensacola, Florida, August 12-21, 1970, Dr. Williams Collins presented an overview of habituation of vestibular responses in animals and humans, which became the reference for all subsequent studies on vestibular habituation. In this review, he noticed that post-rotatory nystagmus (PRN) did not show signs of recovery upon tests performed two weeks following repeated velocity steps. However, in separate studies, the duration of the perceived sensation of rotation appeared to return to quasi-normal three months after the end of the habituation protocol. In the present study, we investigated the long-lasting effects of a vestibular habituation, both on vestibulo-ocular reflex (VOR) and motion perception, over a period of 9-12 months following a bidirectional repeated rotation protocol. We also used a unidirectional habituation protocol, with the non-habituated side being used as control.
METHODS: This study was performed in ten healthy volunteers. Pre-Test: Prior to the habituation protocol, the gain of saccades, smooth pursuit, and optokinetic stimuli, and the gain and phase of VOR in response to sinusoidal oscillations at 0.02, 0.04, 0.08, 0.12, 0.2, and 0.4 Hz in the dark were evaluated. On day one of the habituation protocol, the subjects were exposed to two velocity steps of 80 deg/s in the dark, one in CW and one in the CCW direction. Vestibular Training: Subjects were then exposed to either bidirectional or unidirectional habituation protocols. The bidirectional habituation protocol included a series of ten 80 deg/s velocity steps in yaw, with the chair successively going from 40 deg/s in one direction to 40 deg/s in the other direction in less than 1 s. During the unidirectional habituation protocol the chair was accelerated at 0.3 deg/s/s to a constant velocity of 80 deg/s followed by a deceleration to a complete stop in less than 1 s. This deceleration, also in the form of a 80-deg/s velocity step, was always in the same direction, i.e. CW or CCW. PRN characteristics (gain and time constant) and the duration of perceived rotation were measured for all trials. Subjects were exposed to ten velocity steps during two daily sessions, for five consecutive days at approximately the same time each day, hence a total of 100 velocity steps. Post-Tests: The tests performed prior to the habituation protocol were then repeated the day after the habituation protocol ended, and then approximately one week, two weeks, one month, two months, three months, and nine to twelve months later. The subjective vertical and the magnitude of illusory motion generated by the presentation of visual stimuli were also evaluated before and after the habituation protocol to investigate the transfer of vestibular habituation to cognitive responses.
RESULTS: At the end of the bidirectional habituation protocol, the PRN peak velocity and time constant were reduced by 41% and 64%, respectively, compared to the naive response. A progressive reduction was observed throughout the sessions (acquisition) with a retention of this decrease from one session to the next. Only about a 50% recovery was observed after 9-12 months following the habituation protocol. Duration of perceived motion after chair stop was also reduced by 36% after repeated rotation. However, recovery was complete after nine months. Sinusoidal VOR gain was not affected by vestibular habituation, but sinusoidal VOR phase showed an increase in phase lead at 0.02 and 0.04 Hz, which returned to baseline values within one month. Small but significant alterations in the cognitive responses were also observed after habituation, which recovered within one month. No changes were observed in visuo-oculomotor responses (saccades, smooth-pursuit, optokinetic nystagmus). These results were confirmed with the unidirectional habituation protocol.
CONCLUSIONS :These results demonstrate that the PRN and the sensation of motion are reduced following rotational habituation stimuli, leading to an overall shortening of the response. This reduction persists for a period unusually long compared to other vestibular adaptive processes. However, the recovery is faster for motion perception. This habituation also transfers to sinusoidal VOR and cognitive responses, but their recovery is even faster. These results suggest that the central adaptation for low frequency (sinusoidal) vestibular response, motion perception, and velocity step PRN proceeds from different mechanisms. The information gained from these experiments is helpful for designing and scheduling the protocols for intermittent artificial gravity (centrifugation) during space missions. Indeed, these protocols will expose the astronauts to repeated angular acceleration during centrifuge spin-up and spin-down.
6 STATIC AND DYNAMIC VESTIBULO-OCULAR REACTIONS AFTER PROLONGED MICROGRAVITY Kornilova, L.N.1; Alekhina, M.I.2; Temnikova, V.V.2; Yakushev, A.G.3 1RF SSC-IBMP, R.Ac.Sc., Moscow, Russia; 2RF SSC-IBMP, R.Ac.Sc.; 3Lomonosov's Moscow State University
INTRODUCTION: Under terrestrial gravity the interaction of semicircular canals and otoliths, which perceive linear and angular acceleration is aimed at the creation of adequate model of visual perception and spatial orientation. In microgravity activation of otoliths is minimal because of absence of a natural stimulus - weight, which surely must have an effect on the responsiveness of semicircular canals. For the study of otolith influence on the semicircular canals'function we used a unique experimental model – microgravity and its consequences.
MATERIALS: The investigations involved 11 ISS-3 to -11 crewmembers after prolonged microgravity (126 to 195 days) and one cosmonaut after 10-day microgravity on days 1(2), 4(5), and 8(9) of readaptation. Age of the cosmonauts varied from 35 to 50 years.
METHOD: The characteristics of a torsional otolith-cervico-ocular reflex (TOCOR) and dynamic vestibulo-ocular reactions (VOR) were determined by electrooculograthy and videooculograthy used synchronously. We calculated: amplitudes of compensatory torsional eye counterrotation with the head inclined 35-40 deg. and keeping it in current position for 15 sec.; velocity of compensatory torsional eye counterrotation with the head rotation around the long axis in horizontal plane with 0,125 Hz frequencies; the amplitude, frequency and duration of the nistagmus during head rotation; gain of vestibulo-ocular reactions – gVOR (ratio of angular velocity of eye counterrotation to the angular velocity of head movements).
RESULTS: The investigations of a static TOCOR revealed, in 2 cosmonauts on days 2 and 5 after flight, the absence of a compensatory eye counterrotation, in 2 cosmonauts - the decrease of the amplitude of eye counterrotation in 50%, and no changes in one. The otolith reflex restoration was revealed in 3 cosmonauts on day 9 after flight. The investigations of dynamic VOR revealed a 2-fold increase of gVOR (0,8-0,9) in 6 cosmonauts on days 2 and 5 after flight. This increase was conditioned by decrease of head movement velocity. In 4 cosmonauts the gVOR was sharply decreased (0,1) or close to 0, in 2 cosmonauts – unchanged. On day 9 after flight the ratio of the head movement velocities to the compensatory eye counterrotation returned to baseline. The vestibular responsiveness on days 2 and 5 after flight, which is characterized by the presence or absence of a marked nistagmus during head rotation was increased in 7 cosmonauts and was decreased in rest of them. On day 9 after flight vestibular responsiveness returned to baseline in all cosmonauts, except one. The comparative analysis of the static and dynamic characteristics of vestibular function revealed a certain regularity in interaction of semicircular canals and otoliths, which has a reciprocal nature.
DISCUSSION: The absence of a static TOCOR or its sharp decrease after flight indicated otolith oppression as a result of central deafferentation of a vestibular afferent signal distorted in microgravity. The alteration in gain of dynamic vesibulo-ocular reactions indicated disturbances in eye-head coordinated movement.
CONCLUSIONS: Postflight investigations revealed the marked disturbances in vestibular function, which are characterized by an increased vestibular responsiveness; oppression of the otolith function; decreased vestibular excitability and altered central mechanisms of intersensory interaction. Postflight data shows that recovery of vestibular function, particularly static otolith reflex, requires a certain time for readaptation to gravity.
7 A COMPARISON OF GRAVITY-DEPENDENT ADAPTATION OF THE ROLL, PITCH AND YAW ANGULAR VOR (AVOR) Yakushin, SB1; Storozh, O1; Xiang, Y2; Raphan, T2; Cohen, B1 1Mount Sinai School of Medicine; 2Brooklyn College, CUNY
In naive animals, the gains of the yaw and pitch aVOR are uniform in all head positions relative to gravity. If the yaw or pitch gains are adaptively changed, however, the gain changes are maximal in the position of adaptation and decrease as the head is oriented away from this position (Yakushin et al. 2005). As previously noted in humans (Schmid-Priscoveanu et al., 2000; Bartl et al., 2005) and rats (Brettler et al., 2000) the roll aVOR gains has a gravity-dependent component even before adaptation. We questioned whether after adaptation the roll aVOR has gravity-dependent characteristics similar to yaw and pitch aVOR. Using four cynomolgus monkeys, the roll VOR gain was decreased by in-phase rotations of the primate and optokinetic drum at 0.25 Hz (circa 12°) for 4 hours while prone, supine, left or right side down and upright. Gains were tested at 0.5 Hz (60°/s) in darkness with animals upright or tilted forward-back, left-right, and in the two intermediate planes. Gravity-dependent gain changes were determined from the amplitude of a sinusoidal fit, where the bias represented the gravity- independent gain changes (Yakushin et al. 2005). The roll aVOR gains of the naive animals were not uniform, being largest in the upright position and decreasing by 5-20%, as animals were tilted 90°away from the upright. Average gravity-dependent gain changes in the plane that included the position of adaptation were only 6.2 circa 1.3%, which is substantially less than similar adaptive gain changes in yaw and pitch (25% and 17%, respectively, Yakushin et al., 2005). Moreover, the gravity-dependent component was not present after adaptation in every head orientation, as with yaw and pitch. The average gravity-independent component was 13.9 circa 9.0%, about half of that previously observed for yaw and pitch aVOR (24-25%, Yakushin et al., 2005). There was no correlation between the amount of the gravity-dependent and independent components. Thus, the roll aVOR has a permanent gravity-dependent component, which is independent of adaptation, and has a smaller capability for gravity-dependent adaptation than the yaw and pitch aVOR. Supported by NIH Grants: DC04996, DC05204, EY11812, EY04148, and EY01867
8 EFFECTS OF WATER IMMERSION ON THE GAZE FIXATION REACTION IN RHESUS MONKEYS Badakva, AM; Miller, NV; Eron, JN RF SRC – Institute of Biomedical Problems RAS
BACKGROUND: The results of immersion studies in humans have shown that this model replicates the effects of microgravity on sensorimotor and neurovestibular functions. Purpose of the present study was to evoluate the influence of water immersion on the gaze fixation reaction in rhesus monkeys during the initial stage of support deprivation.
METHODS: The gaze fixation reaction was studied in rhesus monkeys before and during thermoneutral (34.5*C) water immersion to the mid-chest level (3 animals) or to the neck level (2 animals). The animals were trained to perform conditioned reflex motor task (eye-head-hand coordination) and implanted with electrodes to record their electrooculogram.
RESULTS: The angular vestibulo-ocular reflex gain increased and the head angular velocity decreased significantly in 3 monkeys in 5 h after the start of immersion to the mid-chest level. The gain of the passive angular vestibulo-ocular reflex induced by steps of velocity in darkness were not affected after 5 h immersion to the mid-chest level. Changes in characteristics of the head movements were more pronounced in monkeys in 5 h after the start of immersion to the neck level. Although both gain and head velocity changes could have occurred independently, since they occurred in parallel, it is more likely that one of them was primary, while the other was an adaptive response to the primary change. Since changes in gravity were not a factor in these experiments, changes in proprioceptive inputs could have contributed to or been responsible for producing the both changes - gain and head velocity.
CONCLUSIONS: Thus, water immersion is an adequate microgravity simulation model for studying the effects of support deprivation in monkeys.
9 TESTING OTOLITH FUNCTION: 500HZ BONE CONDUCTED VIBRATION SELECTIVELY ACTIVATES IRREGULAR OTOLITHIC NEURONS AND CAUSES AN EYE MOVEMENT RESPONSE IN HUMANS Curthoys, IS1; Kim, J2; Burgess, AM2; Camp, A2; McPhedran, S2; Attard, M2; McGarvie, L3; Halmagyi, GM3; Iwasaki, S4 1University of Sydney; 2School of Psychology, University of Sydney; 3Royal Prince Alfred Hospital, Sydney, NSW; 4Department of Otolaryngology, University of Tokyo, Tokyo
BACKGROUND Safe, simple fast and specific tests of otolith function have great potential value for evaluating the functional state of the otoliths in the clinic or during prolonged periods of microgravity. Vestibular responses evoked by sound or vibration are of special interest because they are safe, simple and fast. Jombik and Bahyi (2005) have reported that bone-conducted vibration elicits eye movements in humans. What is needed is data to show these responses are specifically otolithic and evidence that the human responses are specifically vestibular.
METHODS Standard methods were used for extracellular recording of primary single neurons in anesthetized guinea pigs in response to bone-conducted vibration delivered by a B-71 bone oscillator cemented to the animal's head and, in many cases, their response to air-conducted stimuli from a Telephonics TDH 49 headphone coupled via a speculum to their external ear. The vibration stimulus was measured by linear accelerometers cemented to the skull. A large number of primary vestibular afferent neurons were identified by their location in the vestibular nerve and their response to natural vestibular stimulation (angular accelerations and pitch-tilts and roll-tilts) and then tested to identify if they were activated by bone conducted vibration. They were classed as semicircular canal neurons if they responded to angular accelerations and otolithic if they had a maintained response to pitch- or roll-tilts.
For the alert humans the responses were eye movements recorded by 3-d scleral search coils or infra- red scleral reflectance or emg activity from close to the inferior oblique eye muscle (OVEMPs) which appears to depend mainly on the activity of the inferior oblique. The stimuli were vibrations delivered by a standard clinical Radioear B-71 bone oscillator or a Bruel and Kjaer 4180 mini-shaker. The responses were averaged.
RESULTS Hundreds of guinea pig primary vestibular neurons were tested to evaluate whether they could be activated by low and moderate intensity bone conducted vibration. Most vestibular neurons were not activated by such stimuli up to the maximum amplitude we delivered (+/- 8g acceleration).
The primary neurons which could be activated by the low amplitude bone vibrations we used were almost exclusively otolith irregular afferents identified by their maintained response to static roll- or pitch-tilts and their location. Since our explorations were concentrated in the superior vestibular nerve most of these neurons were utricular and we have additional evidence of that utricular origin from juxtacellular staining by neurobiotin of some otolithic neurons activated by bone conducted vibration. Neurons in the superior vestibular nerve were activated by BC vibration but could not be activated by intense air-conducted clicks. We conclude that low amplitude bone conducted vibration selectively activates otolithic irregular neurons in the guinea pig.
Do bone conducted vibrations elicit a simple oculomotor response in human subjects? Yes. 3-d scleral search coil recordings and infra-red recordings show stimulus-locked eye movement responses to 7msec 500Hz tone burst vibrations delivered by a B-71 oscillator held between the teeth of subjects. This is a short latency (about 6-8 ms) conjugate, predominantly vertical downward eye movement. A 7 ms 500 Hz tone burst applied by the mini-shaker to the human mastoid elicits an eye movement and an emg response from electrodes under the eyes - an OVEMP response to bone conducted vibration. In both cases these are unlikely to be auditory evoked responses since increasing stimulus frequency with constant peak to peak linear acceleration, reduced the response. Other control data support that interpretation.
These are new oculomotor responses to bone conducted vibration and on the basis of evidence from the neural studies and our tests on human patients we suggest they most likely originate from irregular otolithic afferents and preferentially from receptors around the striola of the utricular macula.
10 CONCLUSION Low amplitude bone conducted 500Hz vibration preferentially activates otolith irregular neurons in guinea pigs and elicits eye movement responses in human subjects which we suggest are otolithic. Bone conducted vibration may be a fast simple and safe way of assessing human otolithic function in the clinic and microgravity.
11 MEASUREMENT OF OTOLITH OCULAR COUNTERROLL WITHOUT HEAD OR BODY RESTRAINTS Brütting, M Research Establishment for Applied Science (FGAN)
BACKGROUND: The measurement of otolith ocular counterroll (OOCR) in humans is usually done in roll-tilted positions of the head or body. For matters of controlling the tilt angle and to avoid activation of the semicircular canals as a consequence of unwanted head movements in static roll-tilt, more or less uncomfortable fixation devices are in use. In this context the question arose, whether in experiments with healthy Subjects (Ss) any fixation is necessary at all or if the Ss might be able to keep the head and trunk stable in various tilted positions by themselves.
METHODS: In the first experiment head movements of fifty healthy Ss in three different head/trunk tilted positions (30°, 45° and 60° roll-tilt angle to the right) without any head or body fixation were measured. Ss were seated on an ordinary chair and wore a covered video-oculography mask to avoid effects caused by visual cues such as horizontal and vertical lines of the surrounding. Ss were instructed to fixate a visual stimulus (LED generated spots) projected to the mirrors of the mask in otherwise complete darkness. The mask was additionally equipped with a head position sensor. Roll-tilt positions of the head were reached through oral instructions by the investigator only. To avoid effects of varying convergence angles a second experiment with a slightly modified setup was conducted. Ss now viewed a single spot on a white canvas in a defined distance (1m) to control convergence. By aiming at the spot on the canvas with a laser pointer which was attached to the mask, an increased accuracy of keeping the head stable in tilted positions was expected.
RESULTS: All Ss were able to reach the given positions in the roll plane with an accepted deviation of 2° in yaw, pitch and roll axis and kept the head adequately stable in the three measured roll-tilt positions for a period of 15 seconds which is sufficiently long enough to gain data of the torsional vestibulo-ocular reflex (tVOR). While roll tilt angles of 30° were performed by head movements only, angles of 45° and 60° were, depending on the individual motility of the neck, reached by a combination of head and trunk movements. During the measurement maximum rotatory movements of below 0.3°/s around the anterior-posterior axis were measured which is below the threshold of stimulating semicircular canals affecting the outcome of OOCR measures. The results prove that in experiments with healthy Ss (no balance disorders nor any diseases concerning the vestibular apparatus) data of OOCR might be gained without using laborious fixation arrangements. The analysis of the tVOR data revealed, that presumably effects of uncontrollable convergence in the first experimental setup caused sporadic and abrupt occurrence of reduced OOCR. Ss reported that they were not always able to keep both LEDs on top of each other by maintaining a continuous convergence angle. Additionally, due to the fact that the LED spots were not adjustable, different interpupillary distances of Ss may have caused different convergence angles, particularly with regard to the short distance between the stimulus and the eyes of approximately 4 cm. Compared to the measurements in the dark in the first experiment the quality of eye-tracking data was increased in the second experiment due to a larger iris coming along with a smaller pupil in the bright surrounding. The results of the head movement data showed no significant improvement in head stability in the second experiment but eased taking the required head/trunk roll-tilt position for the Ss. Spontaneous phases of reduced OOCR, presumably caused by varying convergence angles, did not occur anymore. The analysis of OOCR data showed comparable results to those found in the literature with increasing values from 30° to 60° ranging from 0.6°-7.9° (mean 3.8°) at 30° roll-tilt angle to 0.8°-10.7°°(mean 4.9°) at 60° roll-tilt angle (mean of both eyes). The mean standard deviation of 3 measurements for each subject at roll-tilt angles of 30° was 0.27° (SD 0.09°, range 0.15°-0.75°). At roll-tilt angles of 45° and 60°°values of 0.29° (SD 0.11°, range 0.16°-0.63°) and 0.31° (SD 0.09°, range 0.18°-0.55°) were measured, showing a good reliability for the used method of measuring OOCR.
CONCLUSIONS: The results of the experiments show, that healthy Ss are able to keep the head and trunk stable in certain roll-tilt positions, provided that Ss are not exposed to other movements, e.g. centrifuge rotations. The amount of head movements are negligible small, so that measurements of OOCR should be sufficiently exact. Therefore the need of special fixation devices to keep the head stable in certain roll-tilt positions seems to be unnecessary in experiments with healthy subjects without balance disorders or any functional limitations of the vestibular organ. By omission of restraint systems preparations of experiments can be shortened and the Ss comfort as well as the acceptance to participate in such experiments might be increased.
12 OTHOLITH FUNCTION TESTING: SINUSOIDAL LATERAL DISPLACEMENT DURING 400 DEG/S ROTATIONS. Wuyts, FL; Vanspauwen, R; Jansen, E; Van de Heyning, P University of Antwerp
During the past years, we investigated the utricular function based on the protocol as described in Wuyts et al, (2003), that is an extension of the methodology as developed by Clarke et al (1998). In this so called unilateral centrifugation test, subjects are rotated about an earth vertical axis at a velocity of 400 degrees per second. During the ongoing rotation, the subject is translated 4 cm first to the right, and then to the left, along an interaural axis, to a position at which one utricle becomes aligned with the axis of rotation. At this eccentric position, the contralateral utricle is exposed to the combination of gravity and a centrifugal acceleration of 0.4g, corresponding to an apparent roll-tilt of 21.7 degrees. This stimulus induces ocular counter rolling (OCR) which is measured on-line using three-dimensional video-oculography. Not only these extreme positions are taken into account for the analysis, but also all intermediate positions of the rotation axis. As long as the axis of rotation is positioned in between both utricles, the response, i.e. the ocular counter rolling, appears linear. The slope and intercept of this linear response as a function of the eccentricity of the head center (midpoint between both labyrinths), are a measure of the utricular response, i.e. sensitivity and preponderance. In some cases however, while the axis is positioned over one otolith, shifts of the ocular counter roll occur despite the 30s period of constant stimulation. Moreover, a slow delay is present that suggests hysteresis of the response. Therefore, a new stimulation paradigm has been used where a slow sinusoidal lateral translation (0.0125 Hz) of the rotation axis is imposed on each subject, while the chair rotates at 400 degrees per second. Given these new stimulus form, we will investigate gain and phase of the OCR at the imposed sinusoidal stimulus. Possible disconjugacy between the ocular counter rolling of both eyes will additionally be investigated.
13 THE EFFECT OF ANGULAR VELOCITY ON BRAIN COGNITIVE PROCESSING: AN ERP STUDY Wang, Lin-JIe; Zhang, Dan; Guo, Jian-Ping; Cao, Yi; Zhao, Qi; Tong, Fei-Zhou; Niu, Dong- Bin Institute of Space-Medico Engineering
More and more ethological studies performed on vestibular disorder patients and healthy adults accumulated to suggest that cognitive function was involved in the vestibular and ocular motor processing. As the maintenance of intact cognitive processing is most important in space and aviation flight, the effect of long lasting present vestibular stimuli on brain cognitive processing should be explored.
Cognitive brain event-related potentials (ERPs) reflect patterns of neuronal activity at a physiological level and correlate with perceptual and cognitive mechanisms at a behavioral level. These properties make them ideally suit for the research of the brain function variations under vestibular stimulation. In previous experiment we had compared the dynamic changes of auditory cognitive processing under different constant accelerations that were 0.6 degree/sec^2, 0.8 degree/sec^2, 1.0 degree/sec^2 and 1.2 degree/sec^2 and constant 10 degree/sec rotation. It was found that constant 10 degree/sec rotation had an activating effect on the late attention selection process.
In contrast to the activation effect of constant 10 degree/sec rotation, constant angular acceleration had an inhibition effect on the cognitive processes and this inhibition effect may have several levels. Constant 10 degree/sec rotation was the cognitive turning point under different vestibular stimuli in that experiment. As Loose R and Probst T had verified that it was the achieved angular velocity not acceleration that predominated on the perception of visual motion direction during vestibular stimuli, present study applied auditory disjunctive task paradigm under different constant angular velocity rotation to depict the explicit role of angular velocity on brain cognitive processing.
Thirty young volunteers participated in this study and were exposed to randomly dispose constant 30 degree/sec, 60 degree/sec, 90 degree/sec and 120 degree/sec rotation. During each rotation trial the go/no-go Arabian number 2-9 in Chinese pronunciation with about 1000ms interval were delivered binaurally to the subjects by headphone and the subjects were asked to press a button as soon as possible to the odd numbers (target signal) and withhold to the even numbers (non-target signal). It was found that the P300 latency in ERPs induced by the non-target signal was the shortest during constant 30 degree/sec rotation, and the lowest N100 amplitudes and highest P200 amplitudes in ERPs caused by the target signal were also discovered. The N100 latency was shorter than that in constant 90 degree/sec rotation and P200 latency of non-target ERPs were the longest during constant 60 degree/sec rotation. The longest N100 latency, shortest P200 latency, longer non-target ERPs P300 latency and lowest non-target ERPs P200 amplitudes were detected in constant 90 degree/sec rotation.
During constant 120 degree/sec rotation the longest non-target ERPs P300 latency, longest target ERPs P200 latency and longer non-target ERPs P200 latency were presented and the N100 amplitudes and non-target ERPs P200 amplitudes were closed to that of control. As the P300 latency in ERPs induced by non-target signal grew along with the increasing angular velocity and P300 component represented a kind of brain inhibition function to suppress other network during the storage of new information, it was suggested that although the physiological responses in different constant velocity rotation were nearly the same, i.e. viscous drag of the endolymph causing the endolymph to rotate at the same rate as the semicircular canal, the psychological responses were rather different. The angular velocity had linear effect on the brain cognitive processing and the more the velocity was, the more effect on the ERPs endogenous components that reflected the psychological processing. And it was demonstrated that the brain cognitive processing emerged a gradual change from activation to inhibition along with the increased velocity value. Since the velocity storage mechanism is another important characteristics of constant velocity rotation and the vestibular stimuli employed in this study has potentially fixed frequency, further study is needed to settle the impact of velocity storage mechanism and external ultradian rhythm vestibular stimuli on cognition.
14 EFFECT OF THE PROTONOPHORE FCCP ON THE GLUTAMATE RELEASE FROM RAT BRAIN SYNAPTOSOMES UNDER ALTERED GRAVITY CONDITIONS. Borisova, T; Krisanova, N Palladin Institute of Biochemistry NAS of Ukraine
L-glutamate is the most widespread excitatory transmitter in the mammalian central nervous system and essentially mediates all the rapid communications in the CNS. Neurotransmitter uptake from the synaptic cleft occurs via high-affinity sodium-dependent plasma membrane transporters. The transporters primarily use the Na+ - electrochemical gradient across the plasma membranes to drive the concentrative accumulation of neurotransmitters into neurons and glia. Understanding the regulation of neurotransmitter transporters may influence many different areas of neuroscience research and drug use. The potential mechanisms are currently being investigated.
The effects of the protonophore carbonyl cyanide-p-trifluoromethoxyphenyl-hydrazon (FCCP) on the glutamate release from isolated nerve terminals (rat brain synaptosomes) were investigated in control and after centrifuge-induced hypergravity (rats were rotated in a long-arm centrifuge at ten-G during one-hour period). The FCCP induced increase in [Na+]i, depolarized the plasma membrane, dissipated vesicle proton gradient across synaptic vesicles and mitochondrial membrane, caused a fall in both the ATP level and the ATP/ADP ratio. The incubation of synaptosomes with 1 µM FCCP during 11 min resulted in the increase in L-[14C]glutamate level for control animals by 23.0±2.5 % of total accumulated synaptosomal label and 24.0±2.5 % for animals, subjected to hypergravity. FCCP evoked release of L-[14C]glutamate from synaptosomes was not altered in animals exposed to hypergravity as compared to control. Glutamate transport is of electrogenic nature and thus depends on the membrane potential. Depolarization leads to stimulation of glutamate efflux mediated by reversal of the carriers. The high-KCl stimulated L-[14C]glutamate release in Ca2+-free media occurred due to reversal of the high-affinity glutamate transporters. Carrier –mediated release of L-[14C]glutamate (6 min) slightly increased as a result of hypergravity loading (7.7±2.8 % and 11.0±2.0 % of total accumulated label in control and animals, subjected to hypergravity, respectively).
In contrast, high-KCl stimulated L-[14C]glutamate release from synaptosomes preliminary treated with 1 µM FCCP considerably increased from 27.0±2.2 % to 35.0±2.3 % of total accumulated synaptosomal label after centrifuge-induced hypergravity as compared to control animals (Ð≤0.05).
We found competitive nontransportable glutamate transporter inhibitor DL-threo-β-benzyloxyaspartate to inhibit FCCP-high KCL-stimulated release of L-[14C]glutamate. It was suggested the release occur via high-affinity plasma membrane glutamate transporters.
15 EXPOSURE TO MICROGRAVITY DURING SPACEFLIGHT AND SUPPRESSION OF THE TRANSCRIPTION FACTOR XTCF-4 RESULT IN SIMILAR PHENOTYPES IN TADPOLES (XENOPUS LAEVIS). Horn, ER1; El-Yamany, NA2; Wedlich, D3; Kunz, M3; Gradl, D3 1University; 2Zoology Department, Helwan University, Cairo; 3Zoology Department, University of Karlsruhe, Karlsruhe
Space flight experiments have revealed a dorsalization of Xenopus tadpoles caused by microgravity. The ratio of dorsalized tadpoles varied between 25 to 65% of animals during the various flights. After the flights STS-55 (German D-2; 1993), STS-84 (Shuttle-to-Mir SMM06; 1997) and the Soyuz flight Andromède to the International Space Station (2001), dorsalized tadpoles revealed a reduced roll- induced, static vestibuloocular reflex (rVOR), while the rVOR of microgravity exposed tadpoles with normal tails was either not affected or, in older stages, significantly augmented. In addition, dorsalized tadpoles swim in loopings even after reentry to 1g-conditions.
Normalization of body shape took place within 2 weeks. - The oncogenic wnt/ß-Catenin pathway plays a major role in establishing the primary body axis. Activation or repression of this pathway leads to a dorsalized or ventralized phenotype, respectively. One of the nuclear transducers of this pathway (XTcf-4) was knocked down by a morpholino antisense approach. Interestingly, the phenotype of this knock-down as well as the swimming behaviour was similar to that obtained from tadpoles after gravity deprivation. We tested whether the dorsalization in knock-down tadpoles was correlated with a modification of the rVOR. - After unilateral injection of XTcf-morpholino into the two-cell stage, some tadpoles developed upward bended tails. Dorsalized tadpoles swam in loopings. Two weeks after the injection, dorsalized as well as normally developed tadpoles were tested for their rVOR. Prominent morphological and rVOR modifications of morpholino treated tadpoles included that (1) the development of the eye and labyrinth on the treated side was reduced, (2) the rVOR of both eyes was depressed in both dorsalized and normally developed tadpoles. On the injected side, the depression was significantly more pronounced in animals with upward bended tails compared to those with straight tails as it was observed after microgravity exposure. (3) The extent of rVOR depression was positively correlated with the extent of eye asymmetry. (4) Rescue of morpholino treated tadpoles by co-injection of XTcf-4 mRNA was observed for the rVOR as well as for the swimming behaviour.
These results indicate that the observed phenotypes of tadpoles that developed from morpholino-treated 2-cell stages, indeed, are caused by the Tcf-4 knock-down. - We consider the similarity between effects of microgravity exposure and XTcf-4 knock-down on the rVOR as a hint that mechanisms of growth factor actions are sensitive to gravity deprivation during spaceflight. - The German Space Agency supported the space experiments, grant 50WB0323 to Horn.
16 EEG CHANGES IN THE HIPPOCAMPUS FOLLOWING BILATERAL VESTIBULAR DAMAGE Smith, PF1; Smith, PF2; Russell, N2; Horii, A3; Darlington, CL2; Bilkey, DK2 1University of Otago Medical School; 2University of Otago; 3University of Osaka
Theta rhythm in the hippocampus is an 8 Hz rhythm which is believed to be important in synchronizing the activity of single neurons involved in encoding memories for places in space (place cells). In this experiment we recorded hippocampal theta rhythm using chronically implanted electrodes in alert behaving rats that had received either a bilateral surgical deafferentation of the vestibular labyrinth (BVD, n = 6) or a sham operation (n = 6) at least 60 days previously. We found that BVD rats exhibited theta activity with lower power (P < 0.05) and frequency (P < 0.05) compared to controls and that theta was also less rhythmic in lesioned animals (P < 0.05). Measurements of blood corticosterone were similar between BVD and control animals (P > 0.05), suggesting that stress was not responsible for the EEG changes. Although the BVD animals were hyperactive compared to the controls, comparisons were made between lesioned and control animals moving at the same velocity; therefore, differences in movement velocity could not account for the differences in theta. However, despite the major disruption to theta activity, individual place cells in CA1 continued to fire with a periodicity of approximately 8 Hz, although their place fields were highly abnormal. These results suggest that bilateral vestibular loss disrupts theta rhythm, which may account for some of the observed spatial cognitive deficits associated with vestibular damage.
17 REPRODUCTION OF VESTIBULAR STIMULATION DURATION Israël, I1; Capelli, A1; Leboucher, P1; Rivaud-Péchoux, S2; Gaymard, B2 1CNRS; 2INSERM
The vestibular system contributes to spatial orientation, also in complete darkness. However, during the estimation of linear passive self-motion distance in darkness, we found that healthy human subjects mainly rely on time. Furthermore they replicate also stimulus duration when requested to reproduce previous self-rotation as well as self-translation. We then made the hypothesis that the perception of vestibular-sensed motion duration is embedded within encoding of motion kinetics, and cannot be encoded via a channel separate to that of motion.
The ability to estimate time during passive self-motion in darkness was examined with a self-rotation reproduction paradigm. Healthy subjects (16) were required to replicate through self-driven transport the plateau velocity (PV: 30, 60 and 90°/s) and duration (PD: 2, 3 and 4s) of the previously imposed whole-body rotation (82°-496°) in complete darkness. Because the instruction on velocity might impair the duration reproduction, we added a control experiment with zero velocity, i.e. without concomittant vestibular stimulation. Here the subjects (5) reproduced two successive identical rotations (60°/s peak velocity), separated by a momentary motion interruption (MMI) of the same duration as the plateau seen above.
The first main result was that the plateau duration could not be correctly reproduced. Plateau duration reproductions were always too short, and only half of the subjects exhibited a satisfying plateau duration stimulus-response relationship. On the other hand MMI duration was correctly replicated, and all subjects had a significant stimulus-response MMI duration relationship. It is known that constant self-motion velocity is not immediately perceived, which could explain the short plateau reproductions, but the same time constant applies also to zero-velocity perception after an acceleration step. However the MMI duration reproductions were less short than the plateau reproductions. This demonstrates that the subjective time is shorter during self-motion than without motion.
Furthermore, only 2 subjects did not produce significant stimulus-response regression slopes for the total motion duration of the plateau experiment, and all subjects produced significant slopes in the MMI experiment. This suggests that total motion duration reproduction is "automatic", since it was not requested. There is an important literature about time estimation and attention, mainly based on double tasks (Brown, 1997). We believe that our plateau task was not a dual one, because the subjects were indeed required to reproduce two concurrent variables of the same motion, but those two variables were not conflicting and moreover they were reproduced successively. The subjects first attempted to reach the right velocity, and then just had to keep the joystick at the same position during the right duration. However we observed the classic interference effect (duration under-reproduction), so it cannot be ruled out that the concurrent nontemporal task (velocity reproduction) contributed to the underestimation of vestibular-sensed motion time.
It could be argued that the post-rotatory sensations occurring after the stimulus plateau onset distorted its duration estimate, so what was measured was this distortion. But it is well known that post-rotatory sensations are highly idiosyncrasic, and rapidly adapt and decay, while no difference was found in the plateau duration reproduction during the experiment (of 36 trials). Surprisingly, the subjects did not try to reach as quickly as possible the plateau to reproduce, since the time-to-plateau gain was much higher than unity and the acceleration was low, as if the subjects had tried to avoid passing beyond the stimulus velocity. This could explain the second main result, namely that plateau velocity was quite accurately reproduced. The plateau (or peak) velocity gain was higher than unity only at the smallest PV. This result could partly be attributed to the range effect, but the smallest PV was also the only stimulus whose angles were smaller than 180°. This suggests a new result on the perception of self-rotation velocity.
Our temporal results showed that the subjects could not reproduce what they had to (plateau duration) and did accurately reproduce what they were not requested to (total motion duration). So on one hand whole motion duration is accurately replicated together with motion dynamics, and on the other hand a segment of motion duration cannot be correctly reproduced. This is important to take into account in spatial navigation, and for example in driving or flight simulators: accurate perception of motion duration segments may require more training than for complete motion. But complete motion remains to be define.
18 Acknowledgments: supported by AFIRST (FRANCE-ISRAEL), IFR (Hopital de la Salpetriere), and ACI (Ministere de la Recherche, France). Reference: Brown SW. Attentional resources in timing: interference effects in concurrent temporal and nontemporal working memory tasks, Percept.Psychophys. 7: 1118-1140 (1997)<
19 ADJUSTMENT OF BODY POSITION IN PITCH AND ROLL Thomas, T Massachusetts Institute of Technology
BACKGROUND The most common human body position is upright; therefore we expect the best performance, when subjects are asked to adjust themselves to an upright body position. Further, we expect that the horizontal body positions (face down or up, right or left ear down) are adjusted with higher precision and lower variability than the head-down BP, as the horizontal body positions are more common than the head down position.
METHODS The performance of body position self-adjustments was tested in a tilt chair allowing roll and pitch rotations. Twenty-four subjects participated. In one session they adjusted the upright, left-ear-down, head-down and right-ear-down body position in the roll-plane and in another session the equivalent positions in the pitch-plane. Each body position was adjusted 12 times starting from a head-up and 12 times starting from a head down position. The chair rotated with maximum velocity of 2.8°/s. In a separate experiment six subjects adjusted the SVV continuously during slow full cycles roll rotations at 0.05°/s.
RESULTS All adjusted positions in the pitch plane have a greater variability then those in the roll plane. The performance to adjust the upright body position is best for the roll and pitch plane. But, the precision of the head-down adjustments is greater and the variability lower than the adjustments of horizontal body positions. Additionally, all adjusted positions are affected strongly by the rotation direction. The continuous SVV adjustments show a significant smaller Aubert-Phenomenon when the subjects are turned from upright towards head-down than from head-down towards upright (hysteresis-effect, Schone et al., 1978.)
CONCLUSIONS Estimating the directional sensitivity of the otoliths, by using the variance of the adjusted body positions in roll and pitch, shows that the otoliths are not uniformly sensitive to all directions. A simple geometrical otolith model is used to explain those differences of the adjusted body positions. Further the model relates adjusted body positions to the subjective visual vertical and ocular torsion.
20 TEMPORAL ESTIMATES DURING POST-ROTATORY SENSATION CAPELLI, A; BOBIN, A; ISRAEL, I LPCMV, CNRS-Renault, UMR2858
BACKGROUND: Temporal information is processed by a specialized mechanism called the ''internal clock'' (Church, 1984). In a tapping task performed in darkness, with and without passive self-motion, Israel et al. (2004) found that self-motion influences time estimation. The means of the Inter Push Intervals (IPIs) were significantly shorter for trials with motion than without. Treisman et al. (1990) demonstrated that when repetitive stimuli (visual or auditory) were presented during a temporal estimation task, the internal clock pacemaker was sped and time productions were shorter. So the internal clock may have been sped during self-motion. We also found that for both angular and linear self-motions, the subjects decelerated their pressing rate in the decelerating motion trials, and accelerated their rate in the accelerating motion trials. The difference in the results obtained during accelerated and decelerated linear motion trials which respectively accelerated and decelerated the internal clock is surprising because the otoliths of the vestibular system confuses acceleration in a direction and deceleration in the other. However self-rotation acceleration polarity is a parameter which can be detected by the semi- circular canals and it influences time counting. The role of the somatosensory system cannot be neglected in this timing perturbation. In the present work, a tapping task during post-rotatory sensation in darkness was first designed to test only the effect of the vestibular sensation (i.e. almost without somatosensory contribution) on the estimation of temporal intervals.
METHODS: Each trial consisted in 3 successive phases: without motion, with angular motion, post-rotatory phase without motion. The participants tapped each second without stopping throughout the whole trial. Rotations were executed either at constant velocity (3 levels) or at varying velocity (i.e., with acceleration or deceleration). Each trial was repeated 3 times. We awaited that the slopes of the IPIs (indicating the tapping rate evolution) obtained during the post-rotatory phase would be a) similar to the slopes obtained during decelerated motions b) steeper than during the phase with constant velocity.
RESULTS AND CONCLUSIONS:
The experiment permitted to quantify the post-rotatory sensation force. Adaptation to the post-rotatory sensation through the 3 repeated trials was observed as a decrease of the duration and intensity of the sensation was experienced by most participants. Among the angular motions, constant velocity rotations were those which generated the strongest post-rotatory sensations. High and middle constant velocities were most effective. Large inter-subject differences in the feeling of post-rotatory sensation were found. During the first repetition, for some participants the sensation lasted about 30 seconds whereas for others, it was at most 5 sec. The aim of the study was to examine the effect of the post- rotatory sensation induced by vestibular stimulation on time estimation. We computed the linear regression between the pushing number and the corresponding IPI for all phases and found a vestibular influence on time estimation. During phases with vestibular stimulation (angular motion and post- rotatory sensation phases), the slopes were stronger than those obtained without vestibular sensation (pre-rotation no motion phase). The subjects tapping rate underwent some changes during phases with vestibular stimulation. It is also interesting to note that the regularity of the button presses was significantly more variable during post-rotatory sensation than without (no motion and angular motion phases). The influence of vestibular stimulation on time estimation previously found during transport in darkness seems to be confirmed by post-rotatory sensations. The somatosensory stimulation (weaker during post-rotatory sensation than during passive transport) appeared to be not necessary to create a modification in time estimation. This experiment also confirmed that post-rotatory sensation are very subjective and sensible to factors like time and repetitions. The role of vestibular stimulations on time perception will also be discusssed.
References: Church RM (1984) Properties of the internal clock. Ann.NY Acad.Sci. 423: 566-582 Israel I, Capelli A, Sable D, Laurent C, Lecoq C, Bredin J (2004) Multifactorial interactions involved in linear self-transport distance estimate: a place for time. Int.J.Psychophysiol. 53: 21-28 Treisman M, Faulkner A, Naish PL, Brogan D (1990) The internal clock: evidence for a temporal oscillator underlying time perception with some estimates of its characteristic frequency. Perception 19: 705-743 This work was supported by the ACI program (France).
21 A BAYESIAN MODEL FOR ESTIMATING BODY ORIENTATION FROM VESTIBULAR AND VISUAL INFORMATION MacNeilage, PR; Banks, MS UC Berkeley
BACKGROUND: Otolith signals are a primary source of information for body orientation because they can indicate the direction of gravity with respect to the head. Unfortunately, such signals are ambiguous cues to body orientation because they are also affected by inertial forces when the body is accelerated. The ambiguity can be resolved with added visual information indicating orientation and acceleration with respect to the earth. We have been investigating the means by which the noisy vestibular and visual signals are combined to estimate orientation. Here we present a statistically optimal model of this process.
METHODS: Bayes’ Law prescribes how to use information from noisy signals and from previous experience optimally: p(B | I) ~ p(I | B) p(B) , where B is body orientation and I is the sensory input. The first term on the right side of the equation is the likelihood function characterizing the probability of observing the sensory input if B is the actual body orientation. The second term is the prior distribution, which is the probability of observing B independent of the sensory data. The left side is the posterior probability distribution; the observer should use it to base his/her perceptual judgment. If there are no immediate consequences to the judgment (i.e., no costs or rewards), the maximum a posteriori estimate is typically used. That is, the observer chooses an estimate of body orientation that is most probable given the sensory signals and prior expectations. Thus, we choose the value of B that maximizes p(B | I).
In the Bayesian framework, likelihoods represent the sensory measurements and their uncertainties. We can represent each of the likelihoods in a 2D space with body orientation in one dimension and body acceleration in the other. The likelihood function associated with the otolith signal traces a curve through this space because the most likely orientation and acceleration estimates are those that satisfy the gravitoinertial force equation, F = G + I. Said another way, there is no unique solution for orientation and acceleration based on the otolith signal alone. Likelihood functions associated with other sensory signals convey information about one or the other dimension, but not both. The canal rotation signal (integrated over time) can indicate that one orientation is most likely. Likewise, visual cues to orientation and acceleration specify certain values as most likely.
Priors represent expectations from previous experience. We propose two priors, one acting along each dimension in the orientation/acceleration space. The idiotropic prior specifies an upright orientation as most likely, and the no-acceleration prior specifies zero acceleration. These priors are consistent with behavioral observations: respectively, the tendency for astronauts in zero-G to perceive their own longitudinal axis as upright and the tendency for high-performance aircraft pilots to underestimate the inertial force due to acceleration, as in the somatogravic illusion.
Assuming that the sensory signals are conditionally independent (meaning that their noise sources are statistically independent), the posterior distribution can be expressed as the product of all relevant likelihoods and priors: p(B, A | Io, Ic, Ih, Ia) ~ p(Io | B, A) p(Ic | B, A) p(Ih | B, A) p(Ia | B, A) p(B) p(A) where B is body orientation, A is body acceleration, and Io, Ic, Ih, and Ia are the signals from the otoliths, canals, visual rotation, and visual acceleration, respectively.
RESULTS: The model makes many testable predictions about perceived orientation and acceleration. In recent experiments we tested a few of them and found that 1) manipulating visual signals affects the interpretation of the otolith signal, 2) increasing the uncertainty associated with a given signal causes it to have less influence on the percepts of body orientation and acceleration, and 3) better perceptual precision is gained by using all sensory signals than by using only one signal or switching probabilistically between signals.
22 CONCLUSION: The model successfully characterizes perception of body orientation and acceleration in a variety of situations. Experimental results confirm the prediction that more reliable information is given more weight, consistent with the performance of an optimal Bayesian estimator. In addition, the model includes two different priors that result in qualitatively accurate predictions of known behavioral effects. These findings have implication for the development of display technologies that could prevent spatial disorientation illusions.
We acknowledge AFOSR F49620-01-1-0417 and the MPI for Biological Cybernetics.
23 PERCEPTUAL CENTERING OF BODY SEGMENT ORIENTATION Hanes, DA Legacy Research Center
BACKGROUND: Perceptual illusions resulting from altered gravitoinertial environments or sensory disorders can differ between individuals. Discretely differing perceptual constructs arising from a fixed stimulus condition require a non-deterministic characterization that does not depend solely on the stimulus environment or sensor capabilities. This study characterizes the perception of self-orientation and orientation to gravity in the disorienting environment induced by a visual vection stimulus. Our results predict a finite set of illusions that can result from the stimulus condition.
The perception of self-rotation that stems from viewing a rotating disk can be understood in terms of visual and vestibular convergence in the vestibular nuclei. It is not as clear why the viewer would misperceive the orientation to gravity or relative orientations of body segments, since such illusions cannot be explained purely in terms of sensor capabilities or biomechanics. Nevertheless, DiZio and Lackner (Percept Psychphys 39(1): 39–46) have recorded a discrete set of robust illusions of this type. These perceptual illusions are consistent with the visual stimulus and the constancy of otolithic and somatosensory information, but are influenced by central representations constraining combinations of sensory input that are expected in a normal environment.
METHODS: Illusory and veridical perceptions of orientation can be characterized by perceptual transformations that act on a current orientation estimate to yield an updated perceptual construct. Basic centering transformations will be identified from the experimental data. If X is any self- orientation consistent with the experimental paradigm, then each basic transformation T can act on X to produce an updated perceptual orientation TX. Thus, if X is an allowable perception of some actual stimulus condition (in particular, if X is the veridical perception), then TX is also an allowable perception.
Mathematical completeness demands that we allow perceptual transformations to act on the perception resulting from an earlier transformation. Iterating, we see that we must allow as valid perceptions the outcomes of applying all compositions of the basic transformations to the actual orientation. These compositions form a semigroup S of perceptual transformations. If X is an (actual or perceived) orientation of the subject, then the orbit of X under the operation of the semigroup represents the complete set of orientations predicted to occur as perceptions among subjects viewing the rotating disk in the actual orientation X.
RESULTS: Analysis of the experimental data identifies five basic perceptual centering transformations acting on perception of orientation in the rotating disk experiments. All five transformations center the perceived orientations of body components, the rotating disk, and gravity: two align the perceived visual and inertial rotation axes, one centers the perceived axis of visual rotation in front of the head, and two straighten the perceived neck angle.
The semigroup analysis based upon the identified perceptual centering transformations predicts all of the illusions observed in the experiments of DiZio and Lackner (Percept Psychphys 39(1): 39–46). Moreover, the structure of perceptual centering (1) provides a logical explanation for the occurrence of those misperceptions; and (2) predicts the complete set of perceptions that are expected to occur in a larger sample. A comparison with alternative sets of transformations shows that the identified semigroup is optimal with respect to encompassing all of the observed illusions, limiting the number of predictions of unobserved illusions, and minimizing the number of hypothesized basic transformations. In addition to characterizing the data of DiZio and Lackner (Percept Psychphys 39(1): 39–46), the semigroup analysis predicts illusions in many experimental conditions not yet investigated.
CONCLUSIONS: This study characterizes perceptual illusions of self-orientation in a way that (1) encompasses a finite set of distinct perceptual constructs, each of which is experienced by at least some individuals, and (2) predicts illusions that will occur in analogous environments.
24 An important application will be to the understanding of the illusions experienced by vestibular patients. Likewise, perceptual centering transformations identified in terrestrial experiments may predict illusions to be expected in spaceflight, where the absence of a gravitational reference lends extra weight to the ability to judge orientations from a subjective reference frame. For example, our results indicate that under certain conditions, many astronauts will misperceive a visual rotation axis to be centered in front of the head. In general, our results will indicate environments likely to generate perceptual errors and may lead to tests of individual susceptibility to such illusions.
25 MEASURING THE PERCEPTUAL UPRIGHT WHILE MANIPULATING BODY ORIENTATION AND THE ORIENTATION OF THE VISUAL BACKGROUND RELATIVE TO GRAVITY Dyde, RT; Jenkin, M; Harris, LR York University
The direction of 'up' has been traditionally measured by setting a line, luminous if necessary, to the subjective visual vertical (SVV) - i.e. the perceived axis of gravity. It has been found that the relative direction of gravity, of the observer’s body orientation and the orientation of the ambient visual environment all influence the SVV.
An alternative measure of the upward direction can be generated by determining the orientation of a character at which it is most easily recognised. By taking the letters 'p' and 'd', and determining the two orientations at which they are maximally confused, we can infer the orientation at which they are maximally differentiable. This new method - the oriented character recognition technique (OCHART) - has been used to measure what we have named the perceptual upright (PU). The technique was applied to 11 observers who were upright, lying in repose and supine while a background picture rich in polarity cues to the visual 'up' was presented in a series of 16 different orientations. When all the cues to upright - the body orientation, gravity and the visual background - are aligned, PU and SVV are also aligned. As these three sources of determining up are changed with respect to each other, the effects on PU and SVV are markedly different. In the case of PU the effect of manipulating these three contributors to up is closely predicted by a weighted vectorial sum of the directions indicated by each cue, with the direction of the body being the dominant factor and gravity and vision being roughly equally weighted. For SVV a much more complex and less easily modelled result is found, but one which is dominated by the direction of gravity with residual influences of body and vision. These results suggest that as well as measuring different ‘ups’ PU and SVV differ in their sensitivity to manipulations of the contributing cues. As such PU provides a measure which is more amenable for use as a probe for the function and dysfunction of all the sensory contributors to defining up, for the maintenance of postural balance, and in distortions contingent upon perceptions of relative orientation.
Supported by NASA Cooperative Agreement NCC9-58 with the National Space Biomedical Research Institute, the Canadian Space Agency, and grants from the Natural Sciences and Engineering Research Council of Canada to L.R. Harris and M. Jenkin.
26 EFFECT OF FIELD OF VIEW ON A VISUAL REORIENTATION ILLUSION: DOES THE LEVITATION ILLUSION DEPEND ON THE VIEW SEEN OR THE SCENE VIEWED? Jenkin, HL1; Zacher, JE1; Oman, CM2; Harris, LR1 1York University; 2Massachusetts Institute of Technology
Using York University's Tumbling Room facility we assessed how the field of view (FOV) affected observers' susceptibility to the levitation illusion. The levitation illusion is where supine observers feel upright when lying in a room that is tilted with them such that the room remains visually aligned with their body axis (Howard & Hu, Perception (2001) 30: 583). Observers report that their arms feel weightless when extended, and that objects hanging from the wall in front of them seem to levitate. The levitation illusion is an example of a visual reorientation illusion (VRI) in which the floor surface is misidentified. In microgravity, VRI’s can seriously interfere with astronauts' performance and comfort.
Fifteen observers (age range 21 - 46 yrs, mean =33 yrs) with normal (or corrected-to-normal) vision and normal vestibular functioning either sat in a chair in the middle of the Tumbling Room looking at a wall 4 ft from them (near viewing) or were strapped to a board attached to the opposite wall and viewed the same wall from 8 ft (far viewing). In both conditions observers saw in front of them a wall with a door. To the right of the door there were coat hooks holding a scarf, a hat and gloves on strings, and to the left of the door there was a large calendar. To the left of the observer was a bookcase with books, a table set with dishes and cutlery, and two chairs (one supporting a mannequin). Thus the room provided a clear visual frame and a rich variety of visual information about verticality and the direction of down.
Once the observer was in position, the room and observer were rotated together by 90° about an earth- horizontal axis (corresponding to the pitch axis of the observers) using a computer-controlled, DC servomotor. Rotation accelerations were kept below the detection threshold of the canals (0.5°.s-2).
Observers viewed the wall either unrestricted or through goggles that restricted their FOV by various amounts down to approximately 15x20° in a counterbalanced design. Viewing at twice the distance with half the FOV controlled the content of the visual scene. Free viewing was compared to head fixed for each condition. Data were collected via two-way communication between the observer inside the room and experimenter outside. Observers were asked to describe their body orientation and the room’s orientation with respect to gravity. Questions such as: What surface would a dropped ball hit? or: Is the surface you are looking directly at horizontal or vertical? were asked to help the observer understand what was required. Reports that the observer felt supine and the room was pitched back by 90° (veridical perception) were scored as indicating no levitation illusion. Statements that the observer felt upright in an upright room were scored as indicating a levitation illusion. Other responses were categorized as confused.
In both the near and far viewing conditions, 70% of observers experienced the reorientation illusion with unrestricted view (as found in Howard & Hu, 2001). The rate of occurrence reduced systematically with reduction of FOV. However comparing the near and far viewing conditions revealed that this was not an effect of FOV per se but rather of the visibility of polarized visual features: a field of 30x60° was equally effective at inducing a levitation illusion as a 15x30° field viewed from twice the distance and thus including the same visual scene. The incidence of VRI's was enhanced when subjects were allowed to move their head, indicating that the features do not have to be visible all at once.
We conclude that VRI's, such as the levitation illusion depend critically on what can be seen. Also observers were more likely to experience the levitation illusion when free head movement was permitted, allowing more visual cues to orientation to be seen. Users employing virtual reality to induce VRI's will likely have greater success if the FOV is as large as possible; if observers are permitted to expand their field of view further by looking around; and if more polarized features are visible.
Supported by NASA Cooperative Agreement NCC9-58 with the National Space Biomedical Research Institute, the Canadian Space Agency, and grants from the Natural Sciences and Engineering Research Council of Canada to L.R. Harris.
27 VISUAL CUES TO THE DIRECTION OF THE FLOOR: IMPLICATIONS FOR SPACECRAFT DESIGN Harris, LR1; Dyde, RT1; Oman, CM2; Jenkin, M1 1York University; 2Massachusetts Institute of Technology
The floor of a room is the surface that is most likely to provide support and defines the plane in which limbic head direction cells and place cells code orientation and navigation information. What is the contribution of the room's structural features to the perception of which surface this is?
Using the Immersive Visual Environment at York (IVY) twelve subjects were placed in three simulated box-like rooms with no features. The scene was rendered in stereo and was viewed through shutter glasses with a field of approximately 60 x 110 degs. The surfaces that made up the walls, floor and ceiling of the room were each painted a solid colour. The far wall was coloured purple and the other four visible surfaces were randomly assigned one of four colours (red, green, blue or yellow) on each trial. The rooms had a constant depth and a height-to-width ratio that varied from 1:1 to 1:3. The rooms were presented ten times at each of a number of different roll orientations in an interleaved manner. The room was presented for 500ms after which it was replaced with a blank screen of equal luminance. Subjects indicated which surface appeared to be 'the floor' by pressing correspondingly coloured buttons on a game-pad.
To analyse the data each surface was described by its normal vector. The vectors of the surfaces that were chosen for each room structure and orientation were summed to provide the average orientation of the perceived floor for that room configuration.
In weightlessness, when subjects experience visual reorientation illusions, the most overt change in perception is that walls, ceilings, and floors change identities. This can happen in 1-G experiments in a tumbling room too, but the phenomenon has never been quantified before.
We tested three models of how people might determine the floor. Subjects might choose the surface (1) closest to orthogonal to gravity (in which case when our bare room was tilted at 45 deg, the two surfaces equally close to orthogonal to gravity would be equally likely to be chosen as the floor, independent of other features in the room, such as its aspect ratio or depth), (2) closest to orthogonal to gravity on each side of the room's diagonal (in which when the room was tilted so that the diagonal was orthogonal to gravity, the two surfaces on either side of it would be equally likely to be chosen as the floor. The orientation of the diagonal depends on the aspect ratio of the room), or (3) based on a weighting function dependent on each surface's area and orientation. Contrary to expectations, subjects did not necessarily choose the surface closest to orthogonal to gravity or diagonal. Instead the weighted-surface model best described the data.
The perceived direction of the floor seems to depend on the properties of the available surfaces in a predictable manner. Quantifying exactly how these relative weightings are determined and how they might be influenced, may be consequential in limiting visual reorientation illusions and in providing a stable visual reference for orientation when other cues are not available.
Supported by NASA Cooperative Agreement NCC9-58 with the National Space Biomedical Research Institute, the Canadian Space Agency, and grants from the Natural Sciences and Engineering Research Council of Canada to L.R. Harris and M Jenkin.
28 SPATIAL MEMORY DEFICITS FOLLOWING VESTIBULAR DAMAGE: DO THEY RECOVER OVER TIME? Darlington, CL1; Darlington, CL2; Zheng, Y2; Goddard, M2; Smith, PF2 1University of Otago Medical School; 2University of Otago
Previous studies of learning and memory in animals subjected to unilateral or bilateral peripheral vestibular lesions have shown deficits in their ability to remember places in the environment, which may be related to electrophysiological and neurochemical changes in the hippocampus caused by the vestibular loss. Most recently, it has been reported that humans with bilateral vestibular loss exhibit both spatial memory deficits and a bilateral atrophy of the hippocampus (Brandt, T. et al., Brain 128 (2005) 2732-2741). Nonetheless, relatively few studies have systematically examined changes in learning and memory behaviour at different times following vestibular lesions. In the current study, we compared the ability of rats with unilateral or bilateral vestibular deafferentation (UVD or BVD, n = 5 and 4, respectively) or controls (n = 12) to perform in a foraging task in the dark at 3 and 6 months post-op. UVD animals performed significantly worse than controls at 3 months (P < 0.01) but not at 6 months post-op., suggesting that some recovery of normal function had occurred. By comparison, BVD animals could not perform the foraging task and were reluctant to leave their home cage. In further experiments using T maze training, BVD animals (n = 6) again performed significantly worse than controls (n = 6) at 3 weeks, 3 months, and 6 months post-op. (P < 0.05), but gradually improved over the 3 time points, suggesting that in the T maze at least, they show some recovery. These results suggests that unilateral and bilateral vestibular lesions have specific effects in different behavioural tasks used to assess memory and that there may be some recovery of function over time.
29 INCONGRUENT SPACECRAFT MODULE VISUAL VERTICALS AFFECT SPATIAL TASK PERFORMANCE Oman, CM1; Benveniste, D1; Buckland, DA1; Aoki, H1; Liu, AM1; Natapoff, A1; Kozhevnikov, M2 1Massachusetts Institute of Technology; 2Rutgers University
BACKGROUND: Apollo, Shuttle, NASA-Mir and ISS crews anecdotally reported that it is difficult to visualize spatial relationships between the interiors of spacecraft modules whose visual verticals are not coaligned. Traversing between such modules is momentarily disorienting, even months into long missions. Is this because the cognitive map of each module initially learned in ground simulators defines a local 'upright' orientation, and crews have difficulty integrating the local maps if more than a single mental rotation is required ? If instead crews first learned the spacecraft in flight configuration, would they develop an integrated cognitive map from the start, and not have to make difficult mental rotations ?
METHODS: Subjects seated erect wearing a head mounted display viewed the interiors of virtual spacecraft modules. Each 3 meter cubic interior had readily distinguishable floor, wall and ceiling textures defining a locally consistent visual vertical. Two groups of subjects were trained to orient themselves and visualize the interior surfaces, first in each separately, and then with modules joined together in either (Group A, n=19) a 'ground' configuration with visual verticals coaligned or (Group B, n=15) in a 'flight' configuration, where the second module was yawed and pitched with respect to the first. After a verbal guided tour, in successive training trials, subjects practiced visualizing the spatial configuration of the interior surfaces. In each trial, the surface directly ahead was shown so the subject could infer their orientation. Next, the local (and in the joined configuration, the adjacent) module was shown in wireframe outline, and a 'target' texture was presented. The subject was required to appropriately place it in the local (or when joined, the adjacent) wireframe. Between each trial, relative orientation was varied modulo 90 deg. and all surfaces were briefly shown. Next, subjects were tested in the joined configuration without visual feedback between trials. Finally, The ground configuration trained group (A) was retested in the flight configuration and the flight configuration group (B) was restested in the ground configuration, also without feedback.
RESULTS: Most subjects learned to do the orientation/placing task with >90% accuracy. Response time for both groups was significantly (F(1,32)=58) longer (4- 6 sec.) when upright in the flight configuration, and greater still when tilted or upside down, and correlated significantly (R2>.3, p<0.001) with standard 3D Cube Rotation and Perspective Taking Ability test scores.
CONCLUSIONS: Regardless of module orientation during training, both groups apparently remembered each module in a specific visually upright orientation, and when confronted with the twice rotated flight configuration, required additional time to mentally rotate their local maps into an integrated whole. Results have implications both for preflight VR training and spacecraft design. Spacecraft work areas should be designed so that multiple rotations about primary environmental axes are not required to align cognitive reference frames.
Supported by NASA Cooperative Agreement NCC9-58 with NSBRI.
30 THE EFFECT OF THE CONFIGURATION, FRAME OF REFERENCE, AND SPATIAL ABILITY ON SPATIAL ORIENTATION DURING VIRTUAL THREE-DIMENSIONAL NAVIGATION TRAIN Hirofumi Aoki, HA; Charles M. Oman, CMO; Alan Natapoff, AN; Andrew M. Liu, AML Massachusetts Institute of Technology
BACKGROUND: Spatial disorientation and navigation problems in spacecraft have been reported when astronauts move between interior work areas or docked spacecraft whose interior visual verticals have been oriented differently. Complex three-dimensional (3-D) architecture of the spacecraft, lack of the opportunity of preflight 3-D navigation in flight configuration, and the preflight training only in upright orientation with the ground mockups may cause the problems. In order to investigate the effect of configuration on spatial orientation, a simulated emergency egress experiment was conducted with virtual reality techniques.
METHOD: The virtual space station used in the experiment resembled complete configuration of the International Space Station (ISS). Each egress route transited 3 ISS modules and up to 3 changes in local visual vertical. Subjects wearing a HMD could look around, but controlled their body orientation and translation with game-pad buttons. In 12 training trials, each subject learned different routes by following a virtual astronaut tour-guide, maintaining the same body orientation as the tour-guide. During the next 24 testing trials, subjects were inserted at one end of a route and told their destination. They had to point the crosshair at the destination (pointing forward), move there as quickly as possible without a guide, and finally point back toward the start (pointing backward). Smoke obstructed visibility on the final 12 trials. The number of bends (BEND) and the number of planes with respect to the subjects f virtual body posture (BP) of the routes were systematically varied. Before the VR tasks, subjects took Cube Comparisons Test and the Perspective Taking Ability Test to see the correlation with the VR task performance.
RESULTS: No learning effect or smoke effect was seen through the testing trials. In the routes with one horizontal plane (BP = 1) the angular-error of the pointing forward was larger than that of backward. In the horizontal movement like on the ground the subjects had less angular-error after they experienced the routes. In the routes with one pitch rotation (BP = 2), the pointing angular error from the horizontal modules was smaller than that from the vertical modules, suggesting the subjects set their frame of reference on the plane defined by the main modules (US-lab, Columbus, and JEM) and they could orient easier from the reference frame. There was no significant difference between pointing forward and backward in the most difficult routes with two pitch rotations (BP = 3). In those paths the subjects moved between vertical modules so they might be confused when they experienced the routes. The mixed regression analyses were conducted to see the effect of BEND, BP, Cube test score, and the frame of reference (pointing either from horizontal or vertical modules) on the pointing angular-error. Interestingly for the pointing forward angular-error, the effect of BEND, Cube score, and the frame of reference were significant, but BP was not. For the pointing backward angular-error, however, the effect of BP, Cube score, and the frame of reference were significant, but BEND was not. There results suggest that when the subjects pointed forward, they mainly used their mental image of the configuration and the geometric factor of the configuration (BEND) affected the accuracy. However when they pointed backward from the destination after they passed through the routes, the egocentric factor (BP) influenced the angular error.
CONCLUSION: Subjects could integrate the paths only with visual stimulus. Pointing angular error increased with BEND and BP. The pointing angular-error was affected by the geometric and the egocentric factors of the configuration, subjects f spatial ability, and the frame of reference. Supported by NASA Cooperative Agreement NCC9-58 with NSBRI.
31 HEAD TILT POSTUROGRAPHY TO ENHANCE BALANCE CONTROL ASSESSMENT FOR ASTRONAUTS: A CASE STUDY Hwang, EY1; Paloski, WH2 1Wyle Life Sciences; 2NASA Johnson Space Center
BACKGROUND: For many years, we have used a standard clinical computerized dynamic posturography (CDP) protocol to assess recovery of integrated sensory-motor function in astronauts returning from space flight. The most reliable indications of post-flight crew performance capabilities have been obtained from the sensory organization tests (SOTs) within the CDP protocol, particularly SOTs 5 (eyes closed, surface support sway referenced) and 6 (eyes open, surface support and visual surround sway referenced), which are sensitive to changes in availability and/or utilization of vestibular cues. We have observed, however, that some astronauts exhibiting visible signs of incomplete sensory-motor recovery are able to score within clinical norms on standard SOTs 5 and 6 trials, perhaps as a result of cognitive strategies driven by their naturally competitive natures. To improve the sensitivity of the CDP protocol for assessing recovery of integrated sensory-motor function and fitness to return to duties and/or activities of daily living, we have introduced pitch plane head tilt SOT trials to our protocol. In a preliminary study of 5 short duration (less than 11-day missions) astronauts, we showed that they were unable to maintain balance on landing day when performing dynamic head tilt trials, despite scoring within the clinically normal range on the standard SOT trials. The present case report illustrates the advantages of including head tilt trials for assessing sensory-motor recovery in long duration crewmembers.
METHODS: Twice before launch (60 and 30 days) and thrice after landing (1, 3, and 9 days), a long duration space flight (approx. 180-day mission) crewmember performed a set of standard, head erect, clinical SOTs and a set of head tilt SOTs. The head tilt SOTs included standard SOT 2 (eyes closed, fixed support surface) and SOT 5 trials with: 1) head pitched backwards by 20° from the erect position, and 2) head pitching sinusoidally by circa 20° about erect position at 0.33 Hz (synchronized to an audible tone). Performance on each 20 sec trial was quantified by the equilibrium score (EQ), a standard CDP performance measure inversely proportional to the peak A-P sway over the trial. Performance on standard clinical SOTs was compared with the performance of a normative population (n=112), while performance on the head tilt SOTs was compared to an astronaut database (n=19). Comparisons were also made between the crewmember's pre- and post-flight performances.
RESULTS: Before flight, the crewmember's EQ scores for the standard clinical SOTs were within the average range for scores for a normative population, and for the head tilt trials were within the average range for the astronaut population. Specifically looking at SOT 5 head erect results, the crewmember performed below the clinical norm 29 hrs following return from space flight, but recovered to the lower normal range by 76 hrs after landing, and to pre-flight performance by 9 days after landing. However, when performing the head tilt SOTs 24 hrs after landing, the crewmember lost balance during each SOT 5 static tilt trial, and all dynamic tilt trials were waived because of the crewmember’s clearly disrupted sensory-motor coordination. By 76 hrs after landing, the crewmember was able to perform the static tilt trials without losing balance, but lost balance on both of the SOT 5 dynamic tilt trials attempted that day. During the final test session, 9 days after landing, the crewmember’s performance on all head erect and static tilt trials had returned to pre-flight performance levels, however the crewmember’s performance was still well under pre-flight performance for the SOT 2 dynamic tilt trials, and the crewmember lost balance on two of the three SOT 5 dynamic tilt trials.
DISCUSSION: Previous studies in our laboratory have shown that head tilt SOT trials improve the sensitivity of balance control assessment of competitive, high performing individuals, both in ground based studies and in short duration space flight astronaut studies. This case study of a long duration astronaut supports our earlier findings and also shows evidence of mission duration effects on balance control recovery after return. The pattern of recovery appears to aptly track the re-integration of sensory-motor function, with head erect performance recovering more quickly than static head tilt performance, which, in-turn recovers more quickly than dynamic head tilt performance. This seems logical as each successive test condition presents an increasingly more complex set of sensory-motor/biomechanical conditions for identifying spatial orientation and coordinating movements.
32 CONCLUSION: Head tilt SOT trials in combination with standard clinical SOTs provide a more sensitive posturography test protocol for assessing the balance control recovery of astronauts after return from space flight and for providing clinical advice to the crewmember and flight surgeon regarding fitness for return to duties and/or activities of daily living.
33 FUNCTIONAL AND PERFORMANCE TESTS BEFORE, DURING, AND AFTER LONG-DURATION SPACE FLIGHT Hoffer, ME1; Gottshall, KR1; Clark, J2; Black, O3 1Naval Medical Center San Diego; 2NASA; 3Legacy Clinical Research Center
The international space community has begun to focus on long duration, long distance space flight. Scientific and medical issues are prominent features as we seek to accomplish and schedule these missions. One year ago, a group of Russian, American, and Canadian Scientists met at NASA to begin to describe which vestibular tests would be necessary to assess the function and performance of Astronauts involved in long duration and long distance space missions. This group was also tasked with devising some in-flight tests of vestibular function and some follow-up tests at the time of mission completion. The following issues were utilized by the group to determine the test battery: reliability of the test, information provided by the test, time needed to perform the test, ability of non-scientists to administer the test, and equipment required for the test. Based on these and other pieces of information a test battery was established and tentative time points during the career-span of an Astronaut were provided when each test should be performed; from as few times as once during the Astronaut’s career to as often as several times before, during, and after flight. In this presentation, we will present this matrix, a brief description of the tests, and discuss the international space community’s views of these recommendations.
34 ASTRONAUT SELECTION AND TRAINING TO OPTIMIZE MAINTENANCE OF SPATIAL ORIENTATION Rupert, A1; Clark, JB2; Oman, C3 1Naval Aerospace Medical Research Laboratory; 2National Space Biomedical Research Institute; 3Massachusetts Institute of Technology
During the early X-15 probes into space a NASA astronaut experienced the loss of control of his vehicle followed by impact into the desert. The mishap report documented the most likely cause as loss of spatial orientation. The early astronauts were all highly experienced test pilots familiar with vehicle aerodynamics and recovery from unusual attitudes. This population was intensely screened for sensory acuity and as well as sensory-motor coordination demonstrated by success in the highly competitive test pilot community. Despite medical screening and considerable operational experience the X-15 test pilot, when exposed to unusual acceleration conditions, likely experienced spatial disorientation. The NASA mishap report proposed specific recommendations to avoid future spatial disorientation mishaps in part through improved screening of applicants and in part through specific training in man- rated acceleration devices. Although the NASA recommendations were intended for all pilots of future man-in-the-loop vehicles entering space, these selection and training recommendations have receded into distant memory with the complacency of success experienced by the Shuttle program. Early astronauts experienced training in a variety of acceleration devices such as the Human Disorientation Device which could rotate simultaneously around the earth vertical and horizontal axes at velocities up to 60 rpm. Such devices were not only used for training, but also had been used for establishing continued fitness-for-duty in the astronaut corps when medical conditions indicated. Over the past 15 years the Naval Aerospace Medical Research Laboratory has received medical referrals of pilots experiencing spatial disorientation during flight, many of whom had normal vestibular function tests using the currently available and accepted tests of vestibular function. Within this referral population, some otherwise normal pilots displayed abnormal perceptions when exposed to dynamic changes in gravitoinertial force levels. At this point it was realized that the medical community did not have at its disposal the necessary tools to objectively measure the basis for the perceptions being experienced by referred pilots. Based on the discussion of these referrals, a team of neurotologists and vestibular scientists recommended that the Navy develop a battery of new vestibular tests with an emphasis on otolith function tests that could be used to select out pilots who were at increased risk of experiencing spatial disorientation. This Vestibular Test Battery (VTB) program is composed of quick, easy-to-administer, screening tests to establish canal and otolith function under dynamic conditions and more specific tests to examine those individuals who fail the screening tests or who are referred from medical specialists. The resulting vestibular test battery which is currently developing normative data for the Navy pilot population includes a variety of angular, linear and combined angular-linear accelerators in the presence and absence of visual experiences including vection fields. Following normative data development pilots will be followed longitudinally through their flying career to determine acceptable limits for each test of vestibular function. This presentation will discuss specific recommendations from NASA’s first probable SD mishap report, astronaut recommendations concerning SD, the US Navy experience concerning the large body of information available concerning illusions experienced by pilots undergoing G transitions and the role of the ongoing Navy vestibular test battery as a tool for selection and continued fitness-for duty . Vestibular selection and training information should be reevaluated in light of the planned return to the moon, possible missions to Mars and the advent of commercial space flight for the civilian sector, all of which pose conditions where dynamic G transitions will become more significant.
35 SPATIAL DISORIENTATION DURING ORBITER LANDING Moore, ST1; MacDougall, HG1; Clark, JB2; Wuyts, FEL3; Lesceu, X4; Speyer, JJ4 1Mt Sinai School of Medicine; 2NSBRI; 3Antwerp University; 4Airbus
BACKGROUND Up to 90% of crewmembers experience spatial disorientation (SD) during reentry and landing of the Orbiter, with prevalence proportional to the length of the mission. This is a critical issue, as Orbiter landing data shows a decrement in performance following microgravity exposure compared to simulated landings in the Vertical Motion Simulator (VMS) at NASA Ames and the NASA Shuttle Training Aircraft. Despite the potential impact on landing operations, the basis of microgravity-related SD is poorly understood. The aim of this project is to obtain basic data on the characteristics of head and eye movements during simulated Orbiter landings, and to develop a high-fidelity model of microgravity-induced SD to improve pilot training for manned landing or docking maneuvers in space.
METHODS We have developed a laptop-based system for tracking eye, head and cabin movements in real time (MacDougall & Moore, Optom & Vis Sci, 2005), and a novel ambulatory model of SD using Galvanic Vestibular Stimulation (GVS), where a pseudorandom (sum-of-sines) current is passed between surface electrodes on the mastoid processes, masking veridical vestibular input to the CNS (MacDougall, Moore et al., Exp Brain Res, 2006). The GVS current generates perceptual illusions and postural instability both qualitatively and quantitatively similar to that observed in astronauts post-flight. Orbiter landings were simulated in a commercial flight simulator (A340) at Airbus in Toulouse, and in the VMS (NASA Ames).
RESULTS A340 Simulator: During the 45 deg banking turn of the HAC (heading alignment circle) maneuver prior to final approach there was a maintained tilt of the head of up to 5 deg in response to the tilt of the visual horizon. In addition, there was a sustained torsional shift in eye position of 6 deg, which preceded the head tilt. The combined head and eye tilt acted to orient the eye to the scene-derived visual vertical, with a gain of approximately 25%. VMS: During final approach the pilot primarily fixated the target cursor on the head up display (HUD) with occasional glances at the primary flight display. During a simulated HUD failure, the pilot fixated the aim point (a visual aid for correct glide slope) before the runway and the start of the runway, and as the altitude for the flare maneuver approached (2000 ft) the pilot switched to alternate fixations of the start and end of the runway. Presumably the changing angle subtended by these points provided an estimate of the orientation and speed of the approach. GVS: Subjects underwent GVS during dynamic posturography (N=12) and functional locomotor tests (N=20) as performed on astronauts post-flight. Posturography scores observed in astronauts on landing day did not differ significantly to that generated by GVS in our normal subjects. Subjects with GVS exhibited a 12% decrease in coherence of vertical head translation and pitch (indicative of disrupted head stabilization), an 8% increase in step frequency (due to shorter stride length), and a 0.06 logMAR decrease in dynamic visual acuity while walking on a treadmill; and a 21% increase in time to complete an obstacle course; relative to baseline. These locomotor deficits were also consistent with those observed in astronauts post-flight. A pilot subject performed ‘orbiter’ landings in the A340 simulator while exposed to GVS. The perceptual illusions of self- and surround motion generated by GVS were evident in the increased roll of the aircraft during final approach, and there was marked yaw oscillations during rollout.
CONCLUSIONS These preliminary results suggest that GVS generates postural and locomotor deficits, and erroneous control inputs during simulated orbiter landings, consistent with performance following microgravity exposure, and may prove useful in training future astronauts to enhance performance in the presence of SD. Supported by NASA grant NNJ04HF51G and NSBRI Tactical Integration and Planning grant through NASA NCC 9-58 (Steven Moore).
36 INFLUENCE OF TACTILE SENSORY SUPPLEMENTATION ON CONTROLLING UPRIGHT STANCE DURING POSTURAL PERTURBATIONS Black, FO1; Stallings, V1; Wood, SJ2 1Legacy Clinical Research & Technology Center; 2NASA Johnson Space Center
Disruption of balance control is one of the most significant, deleterious post-flight manifestations of sensorimotor adaptation to microgravity. The purpose of the tongue electrotactile system (Wicab, Inc., Middleton, WI) is to provide the brain with a stable inertial reference in order to resolve ambiguous orientation information for control of body movements in microgravity or following g-level transitions. The system operates by stimulating the tongue surface using a 144-point electrotactile array held against the anterior dorsal tongue. The orientation of a body segment relative to gravity is sensed with the two axis linear accelerometer package, and the input to the electrotactile array is the instantaneous pitch and roll angle derived from a sine function of the linear accelerometer outputs. The purpose of this study was to compare postural control performance when providing orientation cues via tongue tactile displays using sensors attached either to the head or torso. We hypothesized that tactile sensory supplementation derived from sensors attached to the head would optimally improve standing postural performance by stabilizing the head in space. Postural equilibrium was measured with a computerized hydraulic platform in 12 healthy adults (7M, 5F, 25-63 y). Trials (100 s duration with eyes closed) were conducted with the support surface fixed, sway-referenced, during sum-of-sines perturbations (0.01, 0.145, 0.295 & 0.565 Hz, peak 2°/s) or during a combination of sway-referencing and sum-of- sines perturbations. Sway-referencing was performed with the platform rotating equal to AP sway angle, by translating the support surface proportional to AP sway, or by rotating and translating the support surface. The linear accelerometers were either mounted on a head band or on a torso belt. Subjects were required to keep the intraoral display in their mouths on all trials, including those that did not provide tactile feedback. As expected, there were improvements in postural performance, based on peak-to-peak AP sway, when using the TDU. The largest changes in postural performance occurred with the platform in the translate sway-referenced mode with or without support surface rotation. In this case, the peak-to-peak sway was significantly reduced with the accelerometers (sensors) mounted on the torso. We conclude having the sensors located on the torso may be advantageous to control postural equilibrium in conditions that naturally involve head-on-trunk motion, as counter-rotation of the head during fore-aft translational movements. These results suggest that the effectiveness of tactile sensory supplementation for balance prosthesis and vestibular rehabilitation applications may be optimized by accounting for the body segment orientation needed for specific task performance.
ACKNOWLEDGEMENT: This work supported by the National Space Biomedical Research Institute through NASA NCC 9-58 (NA 0702).
37 EFFECTS OF VIBROTACTILE FEEDBACK ON MANUAL CONTROL PERFORMANCE DURING FLIGHT TESTS AND LABORATORY TILT NULLING TASKS Rupert, AH1; Wood, SJ2 1Naval Aerospace Medical Research Laboratory; 2NASA JSC
Integration of concordant and redundant information from multiple sensory channels (somatosensory, vestibular and visual) is critical for spatial orientation and sensorimotor control. Multiple sensory integration takes place with minimal conscious effort in most terrestrial conditions due to the presence of a ubiquitous gravitational reference. In unusual acceleration environments however, somatosensory and vestibular senses frequently present false but concordant information concerning the direction of gravity. The spatial disorientation resulting from this sensory conflict is further compounded by high cognitive demands and severity of risks in these environments. We have been exploring the use of vibrotactile feedback as a means of providing accurate orientation feedback in an intuitive manner while minimizing performance deficits associated with dual-tasking (e.g., monitoring of multiple visual displays). The Tactile Situation Awareness System uses a matrix of tactile stimulators located at different body segments to display motion cues as an aid to maintain spatial orientation in altered sensory conditions. This presentation will review manual control performance with and without TSAS during both operational flight and laboratory tests. Laboratory tests were performed with a simple 4 tactor system during a roll-tilt closed-loop nulling task without normal visual feedback. Vibrotactile feedback was provided when tilt position exceeded predetermined levels in either left ear down or right ear down directions. An hydraulic tilt chair was utilized to provide transient (*45 deg) or pseudorandom (0.01-0.6 Hz) tilt motion disturbances in complete darkness about the naso-occipital axis. Fourteen healthy subjects (7M, 7F) were instructed to align a bar with perceived earth-horizontal during some trials, and use this same bar on other trials to null out tilt motion and maintain upright orientation. RMS error during the nulling trials was significantly lower (p<0.05) when vibrotactile feedback was provided. When the vibrotactile thresholds were based on feed-forward projections of tilt orientation, improvements in control performance were noted with projections *500 msec. A series of in-flight experiments has been performed to test multidimensional tactile displays in both helicopters and fixed wing aircraft. Pilots were able to fly complex maneuvers with no instruments or outside visual references (blindfolded) with less than 20 min of training. Recovery from unusual attitudes solely by tactile cues was trivial. Similar to the laboratory tests, flight tests have demonstrated that feed-forward projections of aircraft position significantly optimized helicopter hover performance. We conclude that vibrotactile displays incorporating position and velocity can be optimized for maintaining orientation control in the absence of concordant information from exteroceptive systems such as vision and hearing. The matrix can be as complex as full torso vest to provide multidimensional information, or as simple as a belt with only 4 tactors to provide awareness of deviations away from a desired equilibrium point or deviations toward a boundary condition. TSAS is proposed as a countermeasure for space exploration missions to mitigate impaired movement coordination and spatial disorientation following G-transitions. Laboratory tests have proven useful to validate concepts for utilizing vibrotactile feedback for operational aviation applications. In a similar fashion, we propose that enhanced manual control performance with TSAS in challenging high-performance military aircraft operations will validate concepts of integrating vibrotactile feedback for similar manual control tasks during exploration class space missions. Acknowledgement: This work supported by the Office of Naval Research and the National Space Biomedical Research Institute through NASA NCC 9-58.
38 GALVANIC VESTIBULAR STIMULATION AS A MODEL FOR SPACE ADAPTATION SYNDROME MacDougall, HG; Moore, ST Mount Sinai School of Medicine
BACKGROUND: The balance and locomotor difficulties experienced by astronauts with Space Adaptation Syndrome (SAS) are obvious to the casual observer. Even after short duration (shuttle) flights the cautious bearing of crewmembers descending the stairs of the orbiter, the shuffling broad- based gait, and the 'strapping-down'of the head to the trunk are evident; more so following extended International Space Station (ISS) missions. Post-flight balance and locomotor dysfunction has been categorized as a significant risk (priority 2: 'risk of serious health or performance consequences') for future long-duration ISS and exploration class missions, given that the ''capability to egress the vehicle in an emergency or to perform post landing tasks may be compromised by impaired movement and coordination caused by long-term exposure to microgravity' (NASA 2005). Similarities between these symptoms and those that can be produced by Galvanic Vestibular Stimulation (GVS) lead us to investigate the utility of this stimulus as a model for the syndrome.
METHODS: We are able to deliver relatively large amplitude GVS (±5mA) safely and painlessly using methods developed previously to study the eye movement responses. Large surface electrodes (10cm2) over the mastoid processes (as well as an indifferent on the back at the level of C7) are connected to an ambulatory computer controlled constant currant generator at the waist. Stimuli can be randomly generated or can be coupled to the subjects own head movements in a predictable but inappropriate fashion using a head mounted Inertial Measurement Unit (IMU).
RESULTS: Static Balance: The effect of a pseudorandom binaural bipolar Galvanic stimulus generated by a sum of non-harmonically related sine waves on postural control was functionally assessed using computerized dynamic posturography (CDP), and the results compared to vestibulopathic patient populations and astronauts exposed to microgravity. The standardized CDP test battery comprised six sensory organization tests (SOTs) that combined three visual conditions (eyes open, eyes closed, and sway-referenced vision) with two proprioceptive conditions (fixed and sway- referenced support surfaces). Subjects (12) performed 18 randomized trials (3 trials of each of the 6 SOTs) as a baseline, repeated the 18 trials with GVS, and then performed a post-GVS baseline. A 10 min rest period was inserted between each test battery. Anterioposterior postural sway increased significantly and was in the abnormal range (5th percentile) during GVS for SOTs where visual input was compromised (sway-referenced surround) or absent. Postural stability returned to baseline when GVS was removed. An analysis of sensory input scores (somatosensory, visual and vestibular) demonstrated the specificity of GVS in distorting vestibular input to postural control. The SOT scores observed in astronauts on landing day did not differ significantly to that generated by GVS in our normal subjects. GVS also induced a similar pattern of instability on CDP as profound bilateral vestibular loss, although not as severe.
Dynamic Balance: Locomotor and gaze dysfunction commonly observed in astronauts following spaceflight were modeled using two Galvanic vestibular stimulation paradigms: 1) pseudorandom, and 2) head-coupled (proportional to the summed vertical linear acceleration and yaw angular velocity obtained from a head-mounted Inertial Measurement Unit). Locomotor and gaze function during GVS were assessed by tests previously used to evaluate post-flight astronaut performance; dynamic visual acuity (DVA) during treadmill locomotion at 80 m/min, and navigation of an obstacle course. During treadmill locomotion with pseudorandom GVS there was a 12% decrease in coherence between head pitch and vertical translation at the step frequency relative to the no GVS condition, which was not significantly different to the 15% decrease in coherence observed in astronauts following shuttle missions. This disruption in head stabilization likely resulted in the decrease in DVA of 0.06 logMAR, equivalent to the reduction in acuity observed in astronauts 6 days after return from extended missions aboard the International Space Station (ISS). There were significant increases in time-to completion of the obstacle course during both pseudorandom (21%) and head-coupled (14%) GVS, equivalent to an ISS astronaut 5 days post-landing. An attempt to suppress head movement was evident during both pseudorandom and head-coupled GVS while negotiating the obstacle course, with a 20% and 16%, decrease in head pitch and yaw velocity, respectively.
39 CONCLUSIONS: The results of this study demonstrate that GVS generates many of the salient features of post-flight locomotor dysfunction observed in astronauts following short and long duration missions. GVS can be used to quantitatively and qualitatively models postural instability of vestibular origin, and may prove a useful tool for training people to adapt to altered vestibular input.
40 ADAPTIVE CHANGES IN POSTURAL EQUILIBRIUM AND MOTION SICKNESS FOLLOWING REPEATED EXPOSURES TO VIRTUAL ENVIRONMENTS Harm, DL1; Taylor, LC2 1NASA Johnson Space Center; 2Wyle Laboratories
INTRODUCTION: Virtual environments offer unique training opportunities, particularly for training astronauts and preadapting them to the novel sensory conditions of microgravity. Two unresolved human factors issues in virtual reality (VR) systems are: 1) potential "cybersickness", and 2) maladaptive sensorimotor performance following exposure to VR systems. Interestingly, these aftereffects are often quite similar to adaptive sensorimotor responses observed in astronauts during and/or following space flight. Changes in sensory stimulus conditions and the way we interact with the new stimuli may result in motion sickness, and perceptual, spatial orientation and sensorimotor disturbances. Active exploratory behavior in a new environment, with resulting feedback and the formation of new associations between sensory inputs and response outputs, promotes appropriate perception and motor control in the new environment. Thus, people adapt to consistent, sustained alterations of sensory input. Adaptation is revealed by aftereffects including perceptual disturbances and sensorimotor control disturbances. The purpose of the current study was to compare disturbances in postural control produced by dome and head-mounted virtual environment displays, and to examine the effects of exposure duration, and repeated exposures to VR systems.
METHODS: Forty-one subjects (21 men, 20 women) participated in the study with an age range of 21- 49 years old. One training session was completed in order to achieve stable performance on the posture and VR tasks before participating in the experimental sessions. Three experimental sessions were performed each separated by one day. The subjects performed a navigation and ''pick and place' task in either a dome or head-mounted display (HMD) VR system for either 30 or 60 min. The environment was a square room with 15 pedestals on two opposite walls. The objects appeared on one set of pedestals and the subject’s objective was to move the objects to the other set of pedestals. After the subject picked up an object, a pathway appeared and they were required to follow the pathway to the other side of the room. The subject was instructed to perform the task as quickly and accurately as possible, avoiding hitting walls and other any obstacles and placing the object on the center of the pedestal. Postural equilibrium was measured (using the Equitest CDP balance system, Neurocom, International) before, immediately after, and at 1 hr, 2 hr, 4 hr and 6 hr following exposure to VR. Postural equilibrium was measured during quiet stance with eyes open, eyes closed and vision and/or ankle proprioceptive inputs selectively altered by servo-controlling the visual surround and/or support surface to the subject’s center of mass sway.
RESULTS: Posture data was normalized using a log transformation and motion sickness data were normalized using the square root. In general, we found that exposure to VR resulted in decrements in postural stability. The largest decrements were observed in the tests performed immediately following exposure to VR and showed a fairly rapid recovery across the remaining test sessions. In addition, subjects generally showed improvement across days. We found significant main effects for day and time for the composite equilibrium score and for sensory organization tests (SOT) 1, 2 and 6. Significant main effects were observed fordayfor SOT 3 and 5. Although we found no significant main effects for gender (when center of gravity was used as a covariate), we did observe significant gender X timeinteraction effects for composite equilibrium and for SOT 1, 3, 4 and 5. Women appeared to show larger decrements in postural stability immediately after exposure to VR than men, but recover more quickly than men. Finally, we found no significant main effects for type of VR device or for exposure duration, however, these factors did interact with other factors during some of the SOTs. Subjects exhibited rapid recovery of motion sickness symptoms across time following exposure to VR and significantly less severe symptoms across days. We did not observe main effects for gender, type of device or duration of exposure.
CONCLUSION: Individuals recovered from the detrimental effects of exposure to virtual reality on postural control and motion sickness within one hour. Sickness severity and initial decrements in postural equilibrium decreases over days, which suggests that subjects become dual-adapted over time. These findings provide some direction for developing training schedules for VR users that facilitate adaptation, and support the idea that preflight training of astronauts may serve as useful countermeasure for the sensorimotor effects of space flight.
41 CHLORPHENIRAMINE AND EPHEDRINE IN COMBINATION FOR MOTION SICKNESS Buckey, J; Alvarenga, DA Dartmouth Medical School
BACKGROUND: Motion sickness remains a significant problem for those involved in naval, aviation and space operations. Chlorpheniramine is an attractive drug to prevent motion sickness since it is only mildly sedating compared to other antihistamines used for motion sickness. Also, the high potency of chlorpheniramine makes it an ideal candidate for alternate routes of administration (i.e. transdermal or intranasal) as only drugs with relatively low dose requirements can be expected to permeate the skin and achieve therapeutic blood concentrations. We have previously shown that chlorpheniramine is effective against motion sickness, although the most commonly reported side effect is sedation. To assess whether the sedating effect of chlorpheniramine could be reduced and its effectiveness increased, ephedrine was studied in combination with chlorpheniramine to prevent motion sickness. We hypothesized this would produce a more effective, less sedating combination to prevent motion sickness.
METHODS: We studied chlorpheniramine (C) and chlorpheniramine plus ephedrine (CE) as potential motion sickness treatments in a randomized, double blind, crossover trial. Eighteen normal subjects were randomized to six different orderings of placebo, C (12 mg) or CE (12 mg C + 50 mg ephedrine). They ingested the medication 3.25 hours before off-axis vertical rotation. At least one week elapsed between chair rides. Cognitive testing included a battery of objective and subjective tests performed before drug ingestion, at peak drug effect and following rotation.
RESULTS: C significantly increased the time in the chair compared to placebo [6.6 minutes to 10.3 minutes, p<0.01]. The addition of ephedrine did not significant increase chair time further [6.6 minutes to 10.2 minutes, p<0.01]. Subjects reported significantly more sleepiness on the Karolinska sleepiness scale after taking C (3.3 placebo, 4.9 C (p<0.005)) but not with the CE combination (3.3 placebo, 3.1 CE). Subjects reported more side effects (e.g. jitteriness and nervousness) with CE.
CONCLUSION: This studied confirmed the effectiveness of chlorpheniramine against motion sickness. The addition of ephedrine did not further increase effectiveness as measured by the time spent in the chair. Ephedrine combined with chlorpheniramine counteracted the reported sleepiness that typically occurs with chlorpheniramine, but increased the number of side effects reported.
42 SUSTAINED HYPERGRAVITY TO SIMULATE SAS: EFFECT OF G-LOAD AND DURATION Nooij, SAE; Bos, JE TNO Human Factors
BACKGROUND: In previous studies with a total of 10 astronauts, we demonstrated that symptoms of the Space Adaptation Syndrome (SAS) can be induced by long duration centrifugation on earth. After a 60 min. exposure to hypergravity (+3Gx) in a human centrifuge, about 50% of the astronauts, but also of non- astronaut subjects, experienced SAS-like symptoms at 1G again: nausea, dizziness and/or visual illusions, mainly provoked by head movements. This correspondence suggests that vestibular adaptation is required for any kind of gravity transition within the gravitational continuum, and that any G-reduction may elicit symptoms of SAS. This would have clear implications for G-transitions occurring during space flight (use of artificial G, planet's gravity). To gain more insight in the nature of the stimulus causing the SAS-like symptoms, a ground based centrifuge study was recently performed, focusing on the effects of G-level and duration of exposure.
METHODS: Twelve healthy male subjects each underwent four different centrifuge runs varying in dose: 45 min. at 2 and 3G, and 90 min at 2 and 3G. A standardized head movement test was used to measure the after- effect of each centrifuge condition on head angular position and velocity. Subjects made a maximum of 40 head movements in yaw and pitch as part of a base-line and four post run tests. The level of discomfort caused by the head movements (nausea) was rated on an 11-pont scale. Kennedy's Simulator Sickness Questionnaire was used to assess the overall symptom severity after each centrifuge run.
RESULTS: Preliminary results show large differences between the effect of the four centrifuge conditions on movement characteristics. Generally, head movement velocity was inversely related to symptom severity: susceptible subjects performed the head movements more slowly after the hypergravity exposure than in the pretest. Pitch movements were rated provocative whereas yaw movements were not. Although symptom severity differed between subjects, all subjects reported that the effects of both 3G runs exceeded those of the 2G runs. Furthermore, symptoms were more severe after the 90 min exposure at 3G than after the 45 min exposure. This was supported by the total symptom scores.
CONCLUSIONS: With this study we have thus been able to quantify the effect of a gravity-reduction following long duration centrifugation on SAS development, depending on the G-level difference and exposure duration.
43 THE LABORATORY ASSESSMENT OF ANTI-MOTION SICKNESS HISTAMINERGIC DRUGS. MATSNEV E.I., SIGALEVA E.E. ACADEMY SCIENCES OF RUSSIA – STATE RESEARCH CENTER OF RUSSIA - INSTITUTE FOR BIOMEDICAL PROBLEMS. Matsnev, Eduard1; Matsnev, EI2 1Academy Sciences of Russia – State Research Center of Russia - Institute for Biomedical Problems.; 2Institute for Biomedical Problems
BACKGROUND: Last years experiments proved the active participation of histaminergic system in the controle of autonomic vegetative nervous system disturbances in patients with vestibular dysfunctions, especially during ''sensory mismatch'' between visual and vestibular systems (Lacour, 1998). The histaminergic drug ''Betahistine dihydrochloride'' is widely used in clinic for the treatment of the patients with vestibular disorders of different origin (Lacour M., Sterkers O., 2001). The purpose of recent investigation was to evaluate the antimotion effectiveness of ''Betahistine dihydrochloride'' in experimental motion sickness (MS).
METHODS: 10 healthy volunteers in the age of 18 to 22 y.o. (mean age 19,4 y.o.) with high level susceptibility to MS were selected for the investigation. Acute MS was simulated by using Coriolis accelerations (Graybiel, A. et al.,1968; Reschke, M., 1990; Matsnev E.,1996). The susceptibility to MS was measured as a function of length of exposure (in minutes), using a stimulus of constant intensity, i.e., standardized head movements in sagittal plane, while rotating in the chair at a predetermined angular velocity (30 rpm). The diagnostic criteria for grading the severity of acute MS were used (Graybiel A. et al., 1968). Test stopped when participant reached the ''end point'' (Malaise III). The illusion reactions were estimated using 3 level scale. Each subject took 32 mg of ''Betahistine dihydrochloride''. Identical-appearing tablets, placebo (''Lactose'') and drug were used under ''double – blind'' control and administered in randomized sequence, one hour before testing. Participants underwent videonystagmography (VNG) for estimating the duration and slow phase velocity (SPV) of the post- rotational nystagmus, the pursuit eye tracking test (PETT) – (20 deg./s.;0,3 Hz), the latency, velocity and accuracy of saccades.
RESULTS: A t-test demonstrated a significant (P<0,001) increasing the length of Coriolis stimulation exposure in the experimental group (4,46 circa 2,37min.), versus placebo (2,50 circa 1,58 min) and initial data (2,12 circa 1,18 min). The grading of severity of MS was significantly (P > 0,001) less (5,6 circa 2,1 points). versus placebo (12,0 circa 3,9 points) and initial data (12,8 circa 3,9 points). The illusion reactions were in average (1,3 circa 0,6 points) in experimental group, (2,0 circa 0,6 points) – in placebo group and (2,1 circa 0,9 points) initially - (P > 0,001). It was revealed the significant (P > 0,001) improvement of the gain PETT; the velocity and accuracy of saccades increasing, the saccades latency decreasing. It was revealed a significant – (P<0,001) decreasing of SPV: 9, 65 irca 2,09 deg/s in experimental group versus 12,91 circa 2,03 deg/s in placebo group.
CONCLUSIONS: It was found that ''Betahistine'' demonstrated an antimotion sickness effectiveness. Takeda et al., (1987) experimentally showed that hypothalamic histaminergic neurons project directly into the vestibular nuclei in the rat and it was hypothesized that these afferents regulate MS. The investigations of Lacour and Sterkers (2001), clearly showed that increased or imbalanced activity in the vestibular nuclei complexes leads to the activation of the central histaminergic system. This activation occurs via a vestibular-hipothalamo-vestibular loop, which may be important in the control of vestibular function and in the adaptive response to vestibular lesion and environmental changes (''sensory conflict'' in MS). It's important to emphasize that in our investigations ''Betahistine'' didn’t have a sedative effect and provided a high effectiveness of oculomotor activity.
44 MODELING THE ROLE OF VELOCITY STORAGE IN MOTION SICKNESS. Raphan, T1; Cohen, B2; Kaufmann, H2; Dai, M2 1City University of New York (Brooklyn College); 2Mount Sinai School of Medicine
We have shown that the time constant and the orientation properties of the angular vestibulo-ocular reflex (aVOR) are intimately related to the evolution of motion sickness during rolling the head while rotating (Dai et al, 2003), building on the previous work Bles and Bos (1998, 2002). The smaller the time constant, the longer it takes for motion sickness (MS) to build up and achieve an intolerable nauseogenic state. The tolerance of motion sickness and its temporal evolution is also dependent on the relationship of the orientation of slow phase velocity, relative to an estimate of the yaw axis orientation vector. The latter was determined during roll while rotating (RWR) from the angle of the eye velocity vector in three dimensions as it approached zero during the post-movement nystagmus. How these two seemingly disparate factors are combined centrally to explain the temporal evolution of MS to the intolerable nauseogenic state is not clear. The purpose of this study was to develop a model that explains the interaction of these seemingly disparate generators of MS. In the model, MS has been defined as a “pattern vector” whose components are the autonomic features: nausea, sweating, hyper- ventilation, and malaise. Each of these features has been assigned a score ranging from 0 to 20 and the magnitude of the MS is the length of the feature vector in the MS pattern space. The basic assumptions in the model are that the features of MS are dependent on the ‘velocity storage’ component of the aVOR, and that head orientation with regard to gravity controls the velocity storage time constant, TVOR. The orienting lVOR system activates a parametric controller in the nodulus/uvula, which determines the yaw-axis orientation vector. This determines the cross-coupled vertical velocity that shifts the yaw axis orientation of velocity storage toward alignment with the GIA. According to the model, the vector of eye velocity is compared to the spatial orientation of the velocity storage in the cerebellum. If there is disparity between the two, signals are sent to the autonomic system to generate the buildup of MS features through a motion sickness integrator for as long as the error is maintained. Reduction of the time constant is one technique for reducing the buildup of MS. The orientation error signal has been modeled as a vector cross-product of the yaw orientation vector and the eye velocity response from velocity storage as this considers both the magnitude and the angle between the two vectors. The model predicts that during OVAR, MS is continuously generated and builds because the bias velocity is oriented along the head yaw axis, while the yaw orientation vector is aligned close to the spatial vertical. The model also predicts our data showing that the features of MS and the consequent magnitude of MS, build as if it were an integrator when stimulated with both RWR and OVAR. Thus, we have developed a fundamental definition and model of MS, based on our current understanding of how the canals and otoliths activate velocity storage through the vestibular system. The model shows how the spatio-temporal properties of velocity storage could generate the buildup in magnitude of autonomic features of motion sickness and predicts the temporal evolution of MS for motion stimuli without the contribution of the direct vestibulo-ocular pathways.
45 STROBOSCOPIC VISION AS A TREATMENT FOR SPACE MOTION SICKNESS Reschke, MF1; Somers, JT2; Ford, G2; Krnavek, JM2; Hwang, EY2 1NASA Johnson Space Center; 2Wyle
INTRODUCTION: Overall, the results obtained in both the U.S. and the Russian space programs indicate that most space crews will experience some symptoms of motion sickness (MS) causing significant impact on the operational objectives that must be accomplished to assure mission success. At this time the primary countermeasure for MS requires the administration of Promethazine. Promethazine is not a benign drug, and is most frequently administered just prior to the sleep cycle to prevent its side effects from further compromising mission objectives. Clearly other countermeasures for MS must be developed. Currently the primary focus is on two different technologies: (1) developing new and different pharmacological compounds with less significant side effects, and (2) preflight training. The primary problem with all of these methods for controlling MS is time. New drugs that may be beneficial are years from testing and development, and preflight training requires a significant investment of crew time during an already intensive pre-launch schedule. Granted, motion sickness symptoms can be minimized with either of the two methods detailed above, however, it may be possible to develop a countermeasure that does not require either extensive adaptation time or exposure to motion sickness.
Approximately 25 years ago Professor Geoffrey Melvill-Jones presented his work on adaptation of the vestibulo-ocular reflex (VOR) using optically reversed vision (left-right prisms) during head rotations in the horizontal plane. It was of no surprise that most subjects experienced motion sickness while wearing the optically reversing prisms. However, a serendipitous finding emerged during this research showing that the same subjects did not experience motion sickness symptoms when wearing the reversing prisms under stroboscopic illumination. The mechanism whereby stroboscopic vision prevents motion sickness is not clearly understood. However, the fact that no motion sickness was ever noted, suggests the possibility of producing functionally useful adaptation during space flight without the penalty of disabling motion sickness by controlling the rate of the adaptive process by means of an appropriate stroboscopically presented environment.
METHODS: Using a total of 32 subjects a study was designed to investigate the effect of stroboscopic illumination on motion sickness, using either a strobed room light or liquid crystal display (LCD) shutter glasses. Nineteen of these subjects read text while making circa 20° head movements in the horizontal plane (yaw) at 0.2 Hz while wearing left-right reversing prisms while exposed to 4 Hz stroboscopic or normal room illumination (control condition). Motion sickness was scored using the Miller and Graybiel scale and subjective self-ratings. In a simple crossover design, testing was repeated using LCD shutter glasses as the stroboscopic light source with an additional 13 subjects and 6 subjects from the first condition (for a total of 19 subjects). Results: During the experiment with a strobe light, motion sickness scores were significantly lower than in the control condition where normal room illumination was used. Results with the LCD shutter glasses were analogous to those observed when the environment was strobed in an otherwise dark room.
CONCLUSIONS: Stroboscopic illumination reduces the severity of motion sickness symptoms, and shutter glasses with a flash frequency of 4 Hz are as effective as a strobe light. Stroboscopic illumination appears to be an effective countermeasure where retinal slip is a significant factor in eliciting motion sickness. Additional research is currently underway to evaluate the stroboscopic glasses efficacy in a variety of different motion environments. Specifically, carsickness, sickness during the microgravity periods of parabolic flight and sea sickness. Possible mechanisms underlying the effectiveness of the glasses are also being investigated. There is evidence from pilot studies showing that the glasses, when strobed at the 4 Hz frequency, reduce saccade velocity to visually presented targets is reduced by approximately half of the normal values. It is interesting to note that adaptation to space flight may also slow saccade velocity.
46 SUSCEPTIBILITY TO KINETOSIS UNDER REDUCED GRAVITY – A BRIEF REVIEW ON LESSIONS LEARNED FROM FISH AS MODEL SYSTEM Hilbig, R1; Anken, RH2 1University of Stuttgart-Hohenheim; 2University of Stuttgart Hohenheim
BACKGROUND: According to the ''otolith-asymmetry hypothesis'', an individually different susceptibility to sensorimotor disorders under reduced gravity (i.e., space motion sickness, a kinetosis) may be caused by left to right differences in the mineralization of inner ear otoliths/statoliths. Such an asymmetry was proposed to cause, at rest and under 1g earth gravity, slightly asymmetric shearing forces on the utricles, since the respective maculae are not exactly horizontally oriented. A normal posture then would require some central neuronal ''offset-compensation'', which would compensate for the asymmetrical discharge rates. At microgravity, weight differences in the otoliths from one side of the body to the other side would then not anymore be given and the (primary) discharge rates should not be asymmetrical now. A continuing, but now unnecessary neuronal offset compensation, however, would then cause erroneously (secondary) asymmetric discharge rates leading to a central intersensory conflict and in turn to the sensation of kinetosis.
FINDINGS: Using fish as model system, it has been repeatedly shown that some fish of a given batch reveal motion sickness at the transition from hypergravity (3g; centrifuge) to 1g or from 1g to diminished gravity. Employing centrifuge experiments as well as when applying parabolic aircraft flight micro''gravity (0.03-0.05g, i.e., ''low quality microgravity'', LQM), it was clearly shown that kinetotic individuals revealed asymmetric otoliths regarding their size and calcium(carbonate) incorporation. Applying, however, ''high quality microgravity'' (HQM; 10-6g) in the course of a series of drop-tower experiments, otolith asymmetry was not found to be correlated with kinetosis susceptibility. In these experiments, investigations on the threshold of susceptibility to kinetosis were carried out employing varying levels of diminished gravity (from 0.009g until 0.3g) and the ratios of the types of normal/kinetotic behaviour varied in dependence on the G-level. At LQM, many animals showed a normal swimming behaviour and rather few individuals exhibited different kinds of kinetoses (i.e., spinning movements or looping responses), whereas most animals exhibited kinetoses at HQM.
CONCLUSION These findings suggest that the residual gravity present during parabolic flights is sufficient for most fish of a given batch to maintain a vestibulum-related postural control. Indeed, there exists a ''threshold of gravity'' for inducing kinetosis in fish at around 0.15g (no kinetotic behaviour observed beyond 0.3g).
OUTLOOK: The observations made using fish as a model system to contribute to the understanding of human kinetosis suceptibility provide the following outlook: 1. In order to possibly design appropriate countermeasures, the threshold of gravity for human kinetosis susceptibility should be determined. 2. Although the human vestibular system is much less sensitive than the vestibular system of fish (due to their aquatic lifestyle), it should be investigated, if testing, e.g., otolith function at LQM can be used to predict kinetosis suceptibility under HQM during spaceflight.
Our original studies are financially supported by the German Aerospace Center DLR e.V. (FKZ: 50 WB 9997/50 WB 0527).
47 RELEVANCE OF ROTATING ROOM EXPERIMENTS TO VESTIBULAR PATIENT REHABILITATION AND ADAPTATION IN ROTATING SPACE STATIONS Guedry, FE1; Rupert, AH2 1Pensacola FL; 2Naval Aerospace Medical Research Laboratory
An era of examination of visual-vestibular adaptive plasticity began with a study of reflexive adjustments to optically induced visual-vestibular dysmetria (VVD) published in 1969. This VVD paradigm and variations of it have provided a wealth of information about the neurophysiology of adaptive plasticity in freely moving subjects, human and animal. In the period 1959-1969, publication of Pensacola Slow Rotation Room (SRR) experiments described adaptation to a complex stimulus condition that is remarkably similar to the problems of patients during adaptation to vestibular dysfunction. In the rotating room, every head tilt produces a dysfunctional vestibular message: head tilt angular velocity in one plane (canals) and head tilt position change (otoliths) in an almost orthogonal plane. This canal-otolith conflict is similar to messages received when otoconial particles invade the semi-circular canals, so that head tilts induce canal-otolith conflict in patients. Postural control is challenged in the SRR due to pitch, roll and yaw head movements during walking, but also due to linear Coriolis acceleration, which tends to impart lateral movement to a forward moving foot, leg and body, each with different forward velocity. In addition, a changing direction and magnitude of centripetal acceleration is encountered as subject position in the room changes. SRR experiments demonstrated that man can adapt to living in a room rotating at 10 rpm, and described problems encountered during adaptation and during return to earth-normal conditions. The fact that the challenge to perceptual-motor adaptive plasticity in the SRR on earth differs from the rotating Space Station, where astronauts will walk in the plane of rotation, has been described. Based on these past SRR experiments, and on more recent information, recommendations will be made on: (1) selection of ‘good adapters,’ for VVD and SRR paradigms; (2) reducing discomfort during adaptation; (3) interchange of information with therapists involved in vestibular patient rehabilitation; (4) avenues of investigation in new SRR experiments; and (4) an earth orbit rotating Space Station.
48 EFFECT OF RADIUS VERSUS ROTATION SPEED IN ARTIFICIAL GRAVITY Holly, JE Colby College
BACKGROUND: Artificial gravity by centrifugation can lead to perceptual disturbances in the form of motion sickness and/or misperception of motion during head movements, but the degree of perceptual disturbance during centrifugation in 0-g has not been thoroughly investigated, especially when considering centrifuges of different radii. It is known that head movements during on-axis rotation in 0-g cause very little disturbance, despite the fact that the same movements cause significant disturbance in 1-g. Therefore, 1-g experimental results do not apply directly to 0-g without further analysis.
A modeling approach was presented at the Sixth Symposium, demonstrating that the known on-axis differences between 0-g and 1-g can be explained by linear-angular interaction, modeled in a fully three-dimensional manner. The method also explained a previously-puzzling asymmetry in the amount of perceived movement during head turns clockwise and counterclockwise while supine in a clockwise- rotating centrifuge in 1-g. Objective measures that included linear-angular interaction predicted that subjects will report a different amount of perceptual disturbance depending upon the direction of head turn, based solely upon the physics of the movement. After verification of the model by these known experimental results, predictions were made about 0-g. Predicted was that head movements in a centrifuge in 0-g will cause perceptual disturbances more than they do on-axis, but not to the degree experienced in a centrifuge in 1-g.
METHODS: Presented here at the Seventh Symposium are the results of an investigation of the effects of rotation speed and radius on predictions of perceptual disturbances in 0-g, as well as additional results on asymmetries. An analogous modeling approach was used, with additional variables of speed, radius, body position, and direction of head movement. As before, the model expands traditional analyses by incorporating not just the angular cross-coupled vectors, but also the linear vectors, and all linear-angular interactions. Differences between different types of centrifuge runs and head movements were measured by the Twist Factor and the Stretch Factor, measures of the angular and linear motion, respectively, that would be associated with the accelerations being imposed, given the initial perception of stationarity. These factors are objective measures based upon forces and torques, and could be interpreted as indicating the degree of vestibular-proprioceptive mismatch. Equivalently, these factors could be stated as quantifying the degree of conflict between sensory input and estimates by a physics- based internal model. Either way, the Twist and Stretch Factors indicate the disorienting effects of the accelerations of the head and body, and are good predictors of perceptual disturbance, based upon previous work.
RESULTS: One result arising from the research was that, despite the traditional concern about rotation speed alone, the linear gravitoinertial acceleration (GIA) was also found to be a significant factor in the degree of predicted perceptual disturbance. In particular, a head movement at a large radius would lead to a greater degree of perceptual disturbance than the same head movement at a small radius, if the rotation speed is the same. However, the radius effect would be much less prominent in 1-g than in 0-g, because the magnitude of the GIA does not change with radius nearly as much in 1-g as it does in 0-g, due to the constant presence of gravity which sets a higher baseline for perceptual disturbance in 1-g. Further testing showed that predicted disturbance correlated better with total GIA than with centripetal acceleration.
Not surprisingly, rotation speed was also found to be a significant factor in predicted perceptual disturbance. Because GIA was another factor, tests were done with different radii in order to control for GIA so that rotation speed was tested independently, confirming the results. Predicted perceptual disturbance was a function of both GIA and rotation speed as independent variables, with rotation speed carrying more weight.
Additional verification of the model was carried out by testing against known 1-g experimental results on pitch movements during upright rotation on-axis versus off-axis. The result was that the model was able to resolve previously-unexplained differences in reported perceptions for pitch movements on-axis versus off-axis. These differences were found to arise from linear-angular interactions between accelerations, depending on the direction of rotation and the direction of pitch.
49 CONCLUSIONS:Zero-g experiments are costly, and the three-dimensional modeling approach provides simulated data and predictions to aid in designing experiments and countermeasures. Conversely, the 0-g environment can provide a means to test predictions in order to also further our understanding of perceptual disturbances in 1-g.
50 A PARAMETRIC STUDY OF VESTIBULAR STIMULATION DURING CENTRIFUGATION Jarchow, Thomas; Pouly, J; Young, LR Massachusetts Institute of Technology
BACKGROUND Short radius centrifugation, or Artificial Gravity (AG), is a promising countermeasure to the deleterious effects of long duration weightlessness because it treats all the symptoms at once, by attacking the problem at its root. Unfortunately, head turns performed while spinning at high rotation rates trigger a disturbing vestibular response that includes disorienting sensations of self-motion, improper compensatory eye-movements and motion sickness. Previous studies in our laboratory have shown that subjects adapt to repeated exposure to head turns at high rotation rates: The disturbing vestibular side effects are significantly reduced on the second day of exposure. The present study investigates the quantitative aspect of the vestibular side effects associated with AG in order to design an efficient incremental adaptation procedure. As opposed to sequential adaptation, which keeps a constant stimulus, incremental adaptation consists of exposing the subject to an increasing stimulus so that adaptation is achieved with minimal discomfort. Optimization of incremental adaptation requires a quantitative knowledge of the relationship among cross-coupled stimulus (CCS) intensity, neurovestibular response and adaptation. In particular, comparing the relative effect of head angle and centrifuge velocity on the vestibular response, as done in this experiment, is essential to make incremental adaptation more efficient.
METHODS This parametric study of cross-coupled vestibular stimulation aims at demonstrating experimentally that the CCS, defined in the study as the product of centrifuge angular velocity and the sine of the head turn angle, is a valid parameter for characterizing semi-circular canals stimulation by head turns performed during centrifugation. We tested 20 young adults with supine right-quadrant yaw head turns performed in a completely dark environment during short-radius centrifugation. The subject was positioned with head at centrifuge axis of rotation, placing the feet between 160 and 190 cm off-center. We studied the changes in vestibular response and adaptation to head turns at different levels of cross- coupled stimulation. Nine combinations of head-turn angle (20°, 40° or 80°) and centrifuge velocity (12, 19 or 30 rpm) were tested over two consecutive days.
RESULTS There were four key findings: 1. Most of the available measures of the vestibular response decreased significantly between the two experimental days, which demonstrates that significant adaptation was achieved. 2. Large head angles led to longer vertical vestibulo-ocular reflex time-constants than smaller angles, but did not lead to greater adaptation. 3. For head turns to the nose-up position, the perceived body-tilt was, on average, significantly correlated with the true tilt of the gravito-inertial force (GIF) at mid-chest level. 4. The peak slow-phase velocity of the compensatory nystagmus vertical eye-movements, the illusory motion sensation, and the motion sickness difference showed significant correlation with CCS intensity: the larger the CCS, the stronger the vestibular response.
CONCLUSIONS The very high correlation between CCS intensity and neurovestibular responses validates the use of the CCS parameter and shows that head angle and centrifuge velocity are both candidates for the incremented variable during incremental adaptation. Small head angles were found to lead to shorter vestibulo-ocular reflex time-constant than larger angles, which suggests that small head-angles could lead to less discomfort than larger angles would.
This prediction, however, was not supported by the motion sickness results. Adaptation to the vestibular stimulation was successfully achieved over the two experimental days. There was no difference between the effect of centrifuge velocity and sine of head angle on vestibular adaptation but, surprisingly, adaptation was stronger to weaker CCS intensities.
Finally the body-tilt experienced by the subjects, correlated with the true tilt of the GIF at mid-chest level, showed that they were able to perceive the artificial gravity component of the GIF. These results support the hopes for using short radius AG as a countermeasure to weightlessness since, on one hand, the human body interprets it as real gravity and, on the other hand, it seems possible to train humans to 51 ignore the disturbing vestibular effects it generates. In addition, this study suggests that head-angle might be a better choice for the incremented variable during incremental adaptation. Furthermore, as a matter of efficiency for AG training, multiple subjects could be exposed to the adapting rotation rate, with each having an individual head-angle stimulation.
*Supported by the national Space Biomedical Research Institute through a cooperative agreement with the National Aeronautics and Space Administration (NCC9-58).
52 RESPONSE OF AMBULATORY HUMAN SUBJECTS TO ARTIFICIAL GRAVITY (SHORT RADIUS CENTRIFUGATION) Paloski, WH1; Arya, M2; Newby, N2; Tucker, JM1; Jarchow, T3; Young, LR3 1NASA/Johnson Space Center; 2Wyle Laboratories; 3MIT Man-Vehicle Laboratory
BACKGROUND: Prolonged exposure to microgravity results in significant adaptive changes, including cardiovascular deconditioning, muscle atrophy, bone loss, and sensory-motor reorganization, that place individuals at risk for performing physical activities after return to a gravitational environment. Planned missions to Mars include unprecedented hypogravity exposures that would likely result in unacceptable risks to crews. Artificial gravity (AG) paradigms may offer multi-system protection from the untoward effects of adaptation to the microgravity of space or the hypogravity of planetary surfaces. While the most effective AG designs would employ a rotating spacecraft, perceived issues may preclude their use. The questions of whether and how intermittent AG produced by a short- radius centrifuge (SRC) could be employed have therefore sprung to the forefront of operational research. In preparing for a series of intermittent AG trials in subjects deconditioned by bed rest, we have examined the responses of several healthy, ambulatory subjects to SRC exposures.
METHODS: Eleven ambulatory subjects (6M, 5F; age=24-52 yrs, height=155-183 cm, weight=48-84 kg) were tested. Prior to testing, each passed a medical examination and a cardiovascular stress test, and each provided written informed consent. AG was produced by spinning subjects on a 3.0 m radius SRC. Subjects were oriented radially in the supine position (6° head down) so that the centrifugal force was (nearly) aligned with the long body axis. Subjects were secured to a subject station that allowed free translation over approximately 10 cm along the long body axis to ensure full loading of the lower extremities and to allow for anti-orthostatic muscle contractions. The head was not restrained, but no head movements were required of the subjects. While spinning, the subject "stood" on a force plate. The radius of the plate (2.0-2.4 m) and the angular velocity of the SRC (30.6-33.4 rpm) were adjusted for each subject to achieve the desired centripetal acceleration at the feet (2.5 g) and loading gradient along the body (1.0 g at the heart level). Once the subject was secured, the centrifuge was accelerated at 5-10°/sec2, maintained at the desired constant velocity for 60-75 min, and then decelerated at 5- 10°/sec2. Ramp-up and ramp-down times were fixed at 60 sec. During rotation, the subject's cardiovascular responses were monitored via electrocardiogram (ECG), blood pressure, and pulse oximetry. Foot reaction forces in the body z-, y-, and x-directions were collected using a force plate. Motor activity (EMG) data were collected from the quadriceps, the bicep femoris, the tibialis anterior, and the medial gastrocnemius of the right leg. Otolith stimulation was estimated using triaxial accelerometers mounted to the subject station at the level of the subject's ears. Subjective assessments of motion sickness (scale= 1(excellent) to 20 (vomiting), with 10=half way to vomiting) were collected periodically during the spins.
RESULTS: Six of the 11 centrifuge runs (1F, 5M) were completed as planned; five runs (4F, 1M) were terminated early due to subject health concerns (4=pre-syncope, 1=motion sickness). Mean heart rate and blood pressure increased at the onset of rotation from 70.2±3.7 bpm and 85.9±4.1 mmHg to 85.3±3.7 bpm and 101±16 mmHg, respectively. Lower extremity mechanical loading during the spins was greater than that for standing (mean z-axis reaction force was 130±6 % of the subject's body weight), while z-acceleration stimulation of the otolith organs was less than that for standing (6.8±0.08 m/sec2). Active contractions of the antigravity muscles of the upper legs were infrequent, with the quadriceps and bicep femoris groups active only 1.3% and 4.1% of the total time. Active contractions of the antigravity muscles of the lower legs were more frequent, with the tibialis anterior and medial gastrocnemius groups active for 7.8%, and 26.9% of the total time. Motion sickness symptoms were reported during three of the spins, and one spin had to be terminated due to increased nausea, but, apart from the terminated run, the maximum motion sickness score was generally low (1.5±2.2).
CONCLUSION: The results obtained from this ambulatory subject group were consistent with our expectations for the physiological and perceptual responses to prolonged inertial loading along the long body axis. The relatively low incidence of motion sickness symptom development was encouraging for the next phase of testing with bed rest deconditioned subjects, but the high incidence of presyncope among the female subjects suggests that more work needs to be done understanding the cardiovascular responses within this subgroup before subjecting them to inertial loading during deconditioning. We conclude that it is safe to begin testing this set of artificial gravity parameters in male subjects deconditioned by bed rest.
53 MOTOR IMAGERY AS AN ADAPTATION METHOD FOR HEAD TURNS ON A SHORT-ARM CENTRIFUGE Newby, NJ1; Mast, FW2; Natapoff, A3; Paloski, WH4 1Wyle Labs; 2University of Lausanne; 3MIT; 4NASA Johnson Space Center
BACKGROUND: Artificial gravity (AG) has been proposed as a potential countermeasure to the debilitating physiological effects of long-duration space flight. The most economical means of implementing AG may be through the use of a short-arm centrifuge (SAC), (radius =2m or less). For such a device to produce gravitational forces comparable to those on earth requires rotation rates in excess of 20 revolutions per minute (rpm). Head turns made out of the plane of rotation at these rates, as may be necessary if exercise is combined with AG, result in cross-coupled stimuli (CCS) that cause adverse side-effects including motion sickness, illusory sensations of motion, and inappropriate eye movements. Recent studies indicate that people can adapt to CCS and reduce these side-effects by making multiple head turns during centrifuge sessions conducted over consecutive days. However, about 25% of the volunteers for these studies have difficulty tolerating the CCS adaptation paradigm and often drop out due to motion sickness symptoms. The goal of this investigation was to determine whether motor imagery could be used as a pseudo-stimulus for adapting subjects to this unique environment.
METHODS: Twenty-four healthy human subjects (14 males, 10 females), ranging in age from 21 to 48 years (mean 33, sd 7 years) took part in this study. The experimental stimuli were produced using the NASA JSC SAC. Subjects lay supine on this device with nose pointed toward the ceiling and head centered on the axis of rotation. Thus, centrifuge rotation was in the body roll plane. After ramp-up the SAC rotated clockwise at a constant rate of 23 rpm, which produced a centrifugal force of approximately 1 g at the feet. Semicircular canal CCS were produced by having subjects make yaw head turns from the nose up (NU) to the right ear down (RED) position and from RED to NU. Each head turn was completed in about one second, and a 30 second recovery period separated consecutive head movements. Participants were randomly assigned to one of three groups (n=8 per group): physical adapters (PA), mental adapters (MA), or control group (CG). Each subject participated in a one-hour test session on each of three consecutive days. Each consisted of an initial (pre-adaptation) period during which the subject performed six CCS maneuvers in the dark, followed by an adaptation period with internal lighting on the centrifuge (see below), and a final (post-adaptation) period during which six more CCS maneuvers were performed in the dark. For the PA group, the adaptation period task consisted of performing 30 additional CCS maneuvers in the light. For the MA and CG groups the centrifuge was ramped-down to 0 rpm after the pre-adaptation period and ramped back up to 23 rpm before the post-adaptation period. For both groups, the adaptation period task consisted of 30 CCS maneuvers in the light with the centrifuge stationary (so that no cross-coupling occurred). MA group subjects were instructed to vividly imagine as accurately as possible the displacements of the body produced by the pre-adaptation CCS maneuvers including the magnitude, duration, and direction of illusory body tilt, as well as any accompanying levels of motion sickness. CG group subjects were asked to answer low imagery-content (trivial pursuit) questions during each adaptation period head turn. During the 30second recovery period following each head turn, psychophysical data were collected. These included self-reports of motion sickness, of magnitude and direction estimates of illusory body tilt, and of the overall duration of these sensations.
RESULTS: A multilevel mixed regression analysis performed on the response variables indicates that all three groups experienced some psychophysical adaptation across the three test sessions. For illusory tilt magnitude, the PA group exhibited the most overall adaptation, followed by the MA and the CG group. The slopes of these adaptation trajectories by group over day were significantly different from one another. For the duration of sensations, the CG group again exhibited the least adaptation. The rates of adaptation of the PA and the MA groups, however, were indistinguishable: This suggests that the imagined pseudo-stimulus was as effective a means of adaptation as the actual stimulus itself. The MA group’s rate of adaptation to motion- sickness symptoms was also comparable to the PA group’s.
CONCLUSIONS: The use of vivid motor imagery may be an effective method for adapting to the illusory sensations and motion sickness symptoms produced by cross-coupled stimuli. For space-based AG applications, this technique may prove quite useful in retaining astronauts considered highly susceptible to motion sickness as it reduces the number of actual CCS maneuvers required to achieve adaptation.
54 IMPLICATIONS OF SPATIAL SYMMETRIES IN VESTIBULAR PROJECTIONS FOR SENSORIMOTOR BEHAVIORS IN DIFFERING GRAVITATIONAL LEVELS -- REVIEW McCollum, G Legacy Research Center
Vestibular projections have been shown to maintain the mathematical symmetries of physical space. This logical structure suggests that the nervous system constructs the three dimensionality and other properties of physical space in sensorimotor behavior. An analogy is the way that the visual system constructs a three-dimensional cube from the planar line drawing of a Necker cube. This construction of three-dimensional space is independent of gravity.
The symmetry of three-dimensional space is subtle until one considers breaking the symmetry. For example, the direction of gravity strongly breaks physical space into horizontal and vertical.
This review draws implications for orientation and self-motion perception and sensorimotor behaviors in differing gravitational levels, based on evaluations of the symmetry groups of vestibular projections and related studies. We will discuss symmetry groups of vestibular projections, the relationship of symmetry groups to physical conservation laws, and the discrete choice of up and down that changes abruptly for astronauts. Although horizontal and vertical are physically distinguished by gravity, the corresponding neural distinction may be independent of gravity.
SYMMETRY GROUPS
The direct, disynaptic projection from the semicircular canal nerves to neck motor neurons has been evaluated to find its symmetry group. In physics, the mathematics of symmetry groups are a standard way to characterize the fundamental logical structure of space, dynamics, or objects such as snowflakes. This mathematical technique is immediately applicable to physiological data. Evaluation of data on the direct canal-neck projection revealed that the projection embeds rotation and reflection symmetries of three-dimensional space.
The visual and vestibular climbing fiber projection to the uvula-nodulus has been similarly evaluated in a recent study. Although, a priori, the horizontal optokinetic and vertical semicircular canal projections could embed full three-dimensional symmetry like that of the direct canal-neck projection, they do not. Nevertheless, the vestibulo-olivo-nodular projection has two-dimensional rotational and reflection symmetry, although it breaks the symmetry of the three-dimensional visual-vestibular climbing fiber space. This two-dimensional symmetry provides an intrinsic, gravity independent, neural distinction between horizontal and vertical.
The symmetry groups of these projections have direct implications for the perception of orientation and self-motion in zero-g. In addition, they suggest a means for the nervous system to seamlessly follow the laws of physics in multifarious movements, in earth gravity and zero-g. The physical conservation laws of angular and linear momentum and of gravity are associated with spatial symmetry subgroups. It has recently been experimentally confirmed in longitudinal studies of early walking that children tend to integrate these conservation laws separately into locomotor movements. Although the conservation laws hold seamlessly in all environments, it remains to show how symmetry groups are used in sensorimotor behavior.
IMPLICATIONS
An immediate implication of the two-dimensional vestibulo-olivo-nodular symmetry is that the distinction between horizontal and vertical is independent of gravitation. This result is consistent with observations that up and down may suddenly reverse in zero-g. An ability to adduce other cues for choosing up from down may be a skill that makes space adaptation easier for veteran astronauts.
55 Astronauts carry the spatial symmetries of the vestibular projections into different gravitational levels. These symmetry group evaluations suggest that both the full three-dimensional symmetry and the breaking of three dimensional space into horizontal and vertical serve as frameworks to construct a space for sensorimotor behavior and for orientation and self-motion perception in any gravitational level; these implications remain to be investigated thoroughly. In addition, further research will be needed to show how symmetry groups used on earth to guide body movement are modified for use in zero-g and other gravitational levels.
56 VISUALIZING THE ORIENTATION OF OTOLITH RECEPTOR STRUCTURES USING HIGH-RESOLUTION XRAY MICROTOMOGRAPHY Curthoys, IS1; Uzun, H1; Jones, AS1; Bradshaw, AP2; Todd, MJ2; Halmagyi, GM2 1University of Sydney; 2Royal Prince Alfred Hospital
BACKGROUND : The orientation of the gravity-sensing receptor organs of the inner ear - the otolithic receptors comprising the utricular and saccular maculae – in the head is important for understanding their function in normal gravity and microgravity. It has been a challenge because these maculae are very thin membranes in a fluid filled space buried in dense bone. Recently a new method has become available which allows high definition information about the anatomy of the entire labyrinth and shows the orientation of these sensory region by the use of computerized micro- tomography of post-mortem material.
METHODS : The anatomical material consists of guinea pig temporal bones from animals fixed by intracardiac perfusion with 5% paraformaldehyde and 4% glutaraldehyde (which has been shown to cause minimal distortion on the membranes of the inner ear) and then stained in 2% osmium tetroxide for 2 days to allow the micro-CT procedure to visualize the membranes. Some fixed human temporal bones were also scanned with a Skyscan micro-CT requiring 12-15 hour scan times. The scans were segmented and then input to a commercial 3-d imaging program (VGstudiomax) to reconstruct the segmented structures and generate movies of the data. To achieve the very high resolution only very small tissue pieces could be processed so the temporal bone had to be removed from the skull so that information about the orientation of the sensory regions in the head was lost. The solution to that problem was to relate the orientation of the otolithic maculae to the plane of the horizontal semicircular canal since the orientation of the horizontal canal in the head is known.
RESULTS : The prolonged post-fixation of the specimens in osmium tetroxide allowed sufficient osmium to be deposited on the very thin walls of the membranous labyrinth so that this membrane was visible in micro-CT, as well as the sensory regions of the maculae, the ampullae and the nerves to these structures. Examples of axial sections through the temporal bone and stills from some of the movies which have been made from will be presented. The 3-d reconstruction allows the configuration of the utricular and saccular macula to be clearly identified in the labyrinth, in relation to the horizontal semicircular canal and thus be indirectly related to external skull landmarks. The curvature of the receptor surfaces is clearly evident. The nerve to the saccular macula divided in two, as described by de Burlet (1929) with one region supplying the "hook" of the saccular macular travelling in the superior division of the vestibular nerve and the region supplying the elongated extent of the saccular macular travelling in the inferior division of the vestibular nerve.
CONCLUSIONS : Micro-CT provides precise evidence of the three dimensional orientation of membranous structures whose three-dimensional spatial configuration is important for understanding their operation and the linear accelerations which stimulate them
57 THE EFFECT OF DIFFERENCE OF THE CUPULA AND ENDOLYMPH DENSITIES ON DYNAMICS OF CUPULA Kondrachuk, AV1; Sirenko, SP2; Boyle, R.3 1Institute of Physics, Natl.Acad. of Sci.; 2Institute of Nuclear Research, Natl.Acad.of Sci.; 3BioVIS Technology Center and Vestibular Research Facility, Ames Research Center, NASA
PURPOSE It is suggested that the values of densities of cupula and endolymph in semicircular canals are mathematically equal. Since the composition of cupula and endolymph are different, it is unlikely that their densities are identical. Moreover, these densities may change due to the change of pressure, temperature or metabolic processes. Hence, the equality of the densities of cupula and endolymph is approximate. Due to very high sensitivity of cupulo-endolymphatic system (CES), we expect that even small differences of densities can influence the function of semicircular canals, and that this influence depends on the condition of canal stimulation. The work aims to examine this hypothesis and analyze the parameters of the CES and mechanical stimulation under which the effect of the difference of densities on CES functioning could be observed.
METHODS A simplified model of the CES is proposed to account for the different densities of cupula and endolymph. The main assumptions of model are: a) semicircular canal has a form of an isolated solid torus filled with fluid (endolymph) with density ñ1; b) the cross-section of the canal is entirely occluded by a piston (cupula) with the density ñ2; c) the cupula is elastically attached to the wall of the torus; elastic force is proportional to cupula displacement ; c) simplifying we describe the viscous friction of endolymph against the wall of torus by adding the term proportional to velocity of the fluid to the equation of cupula motion. Thus we obtained the equation of oscillator that describes the displacement of cupula. Its effective coefficient of elasticity depends on parameters of rotation and cupulo- endolympahatic system, orientations of gravitational vector and cupula. When ñ1=ñ2, the model has the form of Steinhauzen’s equation of cupula motion. The analysis of the model was focused on two cases of canal stimulation: i) rotation with constant angular velocity w around the axis located at the distance L from the axis of symmetry of the canal; ii) temporal harmonic oscillation of the angular velocity w. In both cases the various mutual orientations of the axes of rotation, canals and gravitational vectors were considered.
RESULTS Since the effective coefficient of elasticity of the equation of CES motion depends on different parameters of stimulation and structure, the cupula dynamics is complex. To simplify the solution we considered the case of small displacements limited to the two general types of stimulations mentioned above. The following main results are: 1) If the densities of cupula and endolymph differ, the CES becomes sensitive to linear and gravity accelerations. 2) In the case of the long-term rotation with the permanent angular velocity the cupula takes a new equilibrium position. This magnitude of the cupula shift depends on difference of densities of cupula and endolymph as well as on gravity, but the effect remains even in the absence of gravity. 3) In the case of harmonic oscillations of the canal we have two effects: i) a new equilibrium position of cupula and ii) the onset of cupula oscillations with multiple frequencies; both effects take place also in the absence of gravity. 4) Comparison with known experimental data showed that similar effects were observed before, but were not explained or explained by other mechanisms. (For instance, the Fernandez & Goldberg (1971) recordings of canal afferents under harmonic 0.05Hz oscillation of canal); and the Petukhov S.V. (1981) measures of cupula displacements in the mockup of the system of semicircular canals built by the similitude method). The data of Fernandez & Goldberg (1971) allowed for estimating the density difference of cupula and endolymph as 0.001-0.0001 g/cm3. For example, such difference of densities will result in generation of double frequency harmonic when L is more or equal to 100cm, if the frequency of canal oscillation is about 1 rad/sec. 5) Possible source of the density difference may be the change of intralabyrinthine pressure. The value of 0.0001 g/cm3 corresponds to extremely small difference of Poisson's ratios of cupula and endolymph equal to 10-7, if the pressure change is about 10mm of w.c.
58 CONCLUSIONS It was shown that even very small density difference of cupula and endolymph may influence the mechanics of the CES due to high sensitivity of the receptors. The change of the CES mechanics may significantly deform the adequate perception of stimuli. For instance, the onset of a new equilibrium position of cupula in the case of the rotation with permanent velocity will be perceived as the presence of additional angular acceleration. The effects of density difference remain in conditions of microgravity. A set of experiments is proposed to test experimentally predicted effects caused by the difference of cupula and endolymph.
59 ASPECTS OF A NEURONAL REGULATION OF INNER EAR OTOLITH MINERALIZATION IN FISH – A BRIEF REVIEW Anken, RH1; Hilbig, R2 1University of Stuttgart-Hohenheim; 2University of Stuttgart Hohenheim
BACKGROUND: The compact otoliths in the vestibular organ of bony fish are composed mainly of the calcium carbonate polymorph aragonite and a small fraction of organic molecules. The latter form a protein matrix, which determines the morphology of an otolith as well as its crystal lattice structure. In contrast to the otoconial masses of higher vertebrates, the physical capacity of compact fish otoliths can be directly assessed by weighing, measuring their size or by determination of their calcium content. Last not least, fish otoliths continue growing during the entire life-span of the animal. Fish are therefore highly suited to investigate, if altered gravity affects otolith growth and in which way such a respective adaptation is effected.
FINDINGS: Fish otoliths grow slower under 3g hypergravity than under normal 1g earth gravity regarding size and calcium incorporation. Additionally, their asymmetry (i.e., differences between the otoliths from the left vs. the right side of the body) becomes diminished. Opposite effects were obtained under orbital or simulated microgravity. Moreover, calcium incorporation stops after vestibular nerve transection, which clearly indicates a neuronal control of mineralization. In the inner ear of fish, calcium is accumulated at the macular tight junctions. We hypothesize, that - in analogy to the blood-brain barrier - the regulated, paracellular release of calcium into the endolymph is based on the permeability of such junctions altered by neuronal activity. Nerve transection or altered gravity also affects calcium carbonate incorporation via the efferent vestibular system by a stimulation/deprivation of inner ear carbonic anhydrase activity leading to an increased/decreased provision of endolymphatic carbonate. Further studies provided (mostly indirect) evidence that the environmental gravity vector guides not only the provision of calcium and carbonate to the otoliths, but also the selection of the lattice structure of calcium carbonate incorporated. Thus, the protein skeleton of otoliths can be adjusted in order to adapt otoliths (mass, structure, fine morphology) to altered gravity. In several cases, a neuronal control of gene expression has been observed, such as the neuronal control of synaptic gene transcription in skeletal muscle. It is therefore possible, that also the provision/selection of the otoliths' proteinacious components is under genetic control.
SUMMARY/CONCLUSION: Summarizing, the findings strongly indicate the existence of a gravity-induced adaptation process affecting the mineralization of fish otoliths in order to maintain the afferent excitation from the otolithic organs in a range that allows neuronal vestibular compensation. In conclusion, otolith mineralization hitherto is the only biomineralization process known that is neuronally regulated in adaptation to an environmental parameter (i.e., gravity).
Our original studies are financially supported by the German Aerospace Center DLR e.V. (FKZ: 50 WB 9997/50 WB 0527).
60 GAZE HOLDING AS A MEASURE OF VESTIBULAR AFTER-EFFECTS IN PILOTS AND GYMNASTS Wetzel, ES1; Hecht, H2 1Johannes Gutenberg-Universität Mainz; 2Johannes Gutenberg-Univerität Mainz, Department of General Experimental Psychology
BACKGROUND: The adverse effects of prolonged space flight could be overcome by short-radius centrifugation. If such centrifugation is applied intermittently, the costs of repeatedly switching between stationary and rotating environments might produce serious side effects, in particular if the desirable dual vestibular adaptation to the two environments is imperfect. The present study was carried out to determine whether after-effects of rotation on the oculomotor system exceed those of the well-examined post-rotational nystagmus (PRN) and optokinetic after- nystagmus (OKAN). Another point of interest was the potential effect of differences in vestibular expertise on such after-effects. Presumably, pilots of gliders and small airplanes and gymnasts constitute vestibular experts by virtue of the extreme vestibular stimulation they receive. The pilots should be trained to tolerate passive vestibular stimulation and to ignore or suppress the information of their vestibular organ; the gymnasts should be trained to control their own active vestibular stimulation and thus may be particularly sensitive to vestibular afferences.
METHODS: Pilots, gymnasts and a control group were tested for their gaze-holding performance before and after short-term rotation. The data of nine pilots, six gymnasts, and nine control subjects was analysed. Seated subjects were rotated around a vertical axis at 0.5 Hz for a period of 30 seconds. They had to fixate their thumb during the rotation to suppress optokinetic nystagmus and possibly minimize velocity storage. Then subjects had to stand up and sit in a different chair outfitted with a chin rest and an infrared eye-tracking device (Arrington Research). A stationary target had to be fixated for 20 seconds followed by five seconds of free gaze-holding in darkness. Eye movements during gaze-holding were video-oculographically recorded. To estimate the extent of the eye movements, the distance of each gaze position from the centroid of all positions was evaluated. The magnitude of the autokinetic effect, which occurred during the fixation task, was measured using a subjective scale.
RESULTS: Short-term rotation had a significant negative effect on gaze-holding performance in the experts of this study (gymnasts and pilots), but it had no such effect in the control group. No significant differences in gaze-holding performance were found between pilots and gymnasts. Rotation significantly increased the magnitude of the autokinetic effect in the control group. The autokinetic effect experienced by experts, on the other hand, was affected to a much smaller extent.
CONCLUSIONS: We found a clear post-rotatory effect on the accuracy of gaze holding. This effect cannot be accounted for by velocity storage: We applied visual suppression during and after rotation and introduced a delay of 30 seconds after being rotated. In addition observers made active movements between rotation and eye movement recording. By all accounts, PRN and OKAN should not be able to explain the results at the time of the gaze-holding task. This study has shown that short-term rotation about an earth-vertical axis had a negative effect on gaze-holding performance in pilots and gymnasts even after the decay of PRN and OKAN. We suggest that the special training of pilots and gymnasts increases the sensitivity of the vestibular system and thus increases effects of vestibular stimulation on the oculomotor system. At the same time, this increase of vestibular sensitivity in experts seems to be counteracted by an internal mechanism to prevent false perceptions and the adverse effects of sensory conflict. The results show that more research is needed on the influence of short-term rotation on oculomotor functioning, especially since astronauts who are to be exposed to short-radius centrifugation should be considered as having a high amount of vestibular training. Studies on the effects of rotation on vestibulo-ocular interaction should not be limited to the evaluation of the characteristics of nystagmus, such as its slow phase gain and its time constant. A study investigating both the PRN and the post- rotational effects measured in this study may serve to reveal the nature of the latter effects. In particular, repeated exposure to rotation should be studied in vestibular experts. 61 EFFECTS OF LONG DURATION FLIGHT ON ORGANIZATION OF HORIZONTAL AND VERTICAL GAZE FIXATION REACTION Tomilovskaya, ES1; Berger, M2; Gerstenbrand, F2; Kozlovskaya, IB1 1RF State Research Center - Institute for Biomedical Problems of the Russian Academy of sciences; 2Innsbruck Institute of Space Neurology
The purpose of the investigation was to explore effects of long-duration space flight on characteristics of the horizontal and vertical gaze fixation reaction (GFR). The investigation was carried out in the framework of Russian-Austrian experiment ''Monimir''. During the test sessions, the human subjects were to perform the task of rapid horizontal (hGFR) and vertical (vGFR) gaze fixation (pGFR) on targets appearing suddenly in periferal vision field at a distance of 160 cm. Targets – 0,5 angular degrees infrared light diods – were presented in a random order in horizontal and vertical plane at 16 angular degrees from the center. Periferal targets appeared after the gaze was fixated on the central target. Characteristics of eye and head movements were recorded using the MONIMIR system (Austria). The investigation involved seven cosmonauts – members of 'Mir' missions. Test sessions were performed four times before launch (R-45, R-30, R-20 and R-10), three times during space flight (FD 24, 105 and 147), and twice after landing (R+2 and +5).
It has been demonstrated earlier (Bizzi et al., 1971-1974), that equally in primates and humans the GFR accuracy and efficiency are dependent on coordination of three GFR constituents, i.e. saccadic eye movement toward the target, head movement in the same direction, and compensatory eye counter- rolling at the moment of gaze stabilization, that is the gaze has already acquired the target but the head is still moving. In its turn, this coordination is governed by several feedback loops, vestibular afferenation being the leading one.
Before flight all the cosmonauts performed GFR in standart form. There was no considerable difference between reactions to horizantal and vertical targets. Temporal and accuracy charecteristics of reaction essentially changed during the flight. Time of gaze fixation increased on 80% and more. Eye and head movement’s velocity in target direction decreased, at the same time velocity of eyes' counter-rolling increased. Koefficient of vestibulo-ocular reflex (Kvor), averaged 1,0+0,03 before flight, sharply increased to the end of the first month of flight and reached during the counter-rolling phase 1,4 (for hGFR) and 4,3 (for vGFR). Later on Kvor tended to decline, however it increased again on the second day after landing (up to 1,7-2,7). Latencies (by 40-60%) and number (50-65%) of corrective saccades during the counter-rolling phase reliable increased. There were obtained essential changes in thestructure of GFR: the number of reactions when the head started to move only after the end of eye movement increased on 50% and amounted 60% (for hGFR) and 80% (for vGFR). General number of reactions, finished with gaze fixation during recoring time (1200 ms), decreased from 98- 100% before flight to 65% (for hGFR) and 35% (for vGFR) to the third month of flight. After landing, most GFR characteristics returned to baseline values, however, on the second day after landing the time of gaze fixation was still high at most and regained the preflight values only on the fifth day. Dynamics of recovery of the other analized characteristics was similar.
Thus, accuracy of eye and head movement coordination in fast gaze fixation reactions sharply decreased in microgravity. Consequently, visual tracking abilities are considerable reduced in microgravity, especially in vertical plane.
62 USEFULNESS OF CURRENT BALANCE TESTS FOR IDENTIFYING BALANCE-IMPAIRED INDIVIDUALS Cohen, HS1; Kimball, KT2; Mulavara, AP3; Bloomberg, JJ4 1Baylor College of Medicine; 2Statistical Design and Analysis; 3National Space Biomedical Research Institute; 4NASA/ Johnson Space Center
BACKGROUND. The literature describes many balance tests, but their true accuracy in teasing apart normals from individuals with balance problems is unknown. No studies in the literature have compared normals to patients on several balance tests in a comprehensive study of specificity and sensitivity of the most common balance tests. This information would be useful for accurate assessment of clinical patients with vestibular and balance disorders and of astronauts shortly after return from space flight. This knowledge will facilitate development of simple but accurate functional balance tests that can be given to astronauts immediately at landing by astronauts or flight surgeons, to patients at home by home health care staff or within an out-patient clinic. Therefore, we gave several balance tests to normals and to patients with known vestibular disorders, to determine which tests best classify individuals as abnormal.
METHODS. Subjects were 40 normals and 40 patients, all adults, diagnosed with vestibular disorders based on the otolaryngologists' clinical examinations, supported by findings from diagnostic tests including, but not limited to, bi-thermal caloric tests and sinusoidal rotatory tests of vestibulo-ocular reflex in darkness. They were seen in an out-patient, tertiary care center that specializes in vestibular and balance disorders. Subjects were given well-known, normed tests that have been described in the literature: computerized dynamic posturography (Neurocom Equitest), the Berg Balance Scale, the Timed Up and Go test, and the Dynamic Gait Index. They were also tested on the new Functional Mobility Test (FMT) developed in our laboratories, which involves rapidly walking through an obstacle course on compliant foam; the dependent measures are time to complete the course and the number of obstacles touched. Tests were given by technicians who were blinded to subjects’ diagnoses.
RESULTS. Scores were examined first using the cut-offs for normal scores described in the literature, and then with Receiver Operating Characteristic (ROC) curves. Using the previously reported norms, no standard test classified more than 77% of subjects as patients or normals correctly. FMT was the most accurate test; it correctly classified 87.5% of patients using the measure of number of obstacles touched and it correctly classified 95% of patients using the measure of time to complete the course. On posturography, Sensory Organization Test 5 (eyes closed, sway referenced motion of the force platform) correctly classified 80% of patients, using the manufacturer’s norms. The Dynamic Gait Index correctly classified 20% of patients, Timed Up and Go correctly classified 7.5% of patients, and the Berg Balance Scale correctly classified 2.5% of patients, suggesting that these scales are not very accurate. Use of norms based on ROC curves sharpen the accuracy of some tests.
CONCLUSIONS. FMT shows promise for development of a field test of balance or for use in the clinic, and may be more useful when combined with other measures. Using the existing norms, none of the standard tests in the literature, including the “gold standard” of computerized dynamic posturography, are really useful for determining which individuals have subtle but functionally significant balance disorders. Tests of gait that are often used by therapists in balance clinics are the least useful. Improved tests would be beneficial for the manned space program and for clinical care. To develop easily administered tests that yield accurate results more work must be done.
ACKNOWLEDGEMENTS. Supported by National Institutes of Health grant DC04167 and the National Space Biomedical Research Institute through NASA NCC 9-58. The staff of the Center for Balance Disorders provided invaluable assistance
63 GLUTAMATERGIC STIMULATION OF THE MEDIAL VESTIBULAR NUCLEUS EVOKES THE INHIBITION OF RESPIRATORY RHYTHM IN THE ISOLATED BRAINSTEM-SPINAL CORD OF NEWBORN RAT Glazkova, EN1; Pyatin, VF2; Rybakov, SV2 1State Medical University; 2Samara State Medical University
BACKGROUND: The vestibular nucleus is mainly responsible for sensing changes in head position with respect to gravity and producing relevant compensatory responses of muscles that control posture and eye movement. In addition, activation of the vestibular nucleus can produce changes in respiratory rate and in the discharge of the phrenic nerve in the adult animals (Miller AD, et al., 1995; Mori RL, et al., 2001). Electrical stimulation of different vestibular subnuclei evokes either increase or decrease ventilation in the rat. In contrast, selective chemical stimulation of specific NMDA receptors of the subvestibular nuclei only elevated ventilatory response (Xu F, et al., 2002). Respiratory excitatory responses are probably mediated by glutamate acting on NMDA receptors in the medial vestibular nucleus (VNM), whereas the neurotransmitters involved in VNM–mediated respiratory inhibition remain unknown. However, the involvement of glutamate in the VNM in respiration modulation in the newborn animal has not been investigated.
METHODS: The present study was conducted on brainstem-spinal cord preparation of 0- to 3-day-old rats. The brainstem and spinal cord were isolated with the animals under deep ether anesthesia. The preparation was continuously superfused at a rat of 2-3 ml/min in a 2-ml chamber with the standart solution artificial cerebrospinal fluid (pH 7,3; equilibrated with 95% O2 and 5% CO2; at +24-25°C). Respiratory activity corresponding to inspiration was monitored at the C4 or C5 motoneuron ventral root (recorded which a suction electrode). Microinjection of glutamate (50 mM/l; 40 nl) dissolved with artificial cerebrospinal fluid were performed through the dorsal surface into the rostral part of the VNM (contralateral and/or ipsilateral).
RESULTS: We observed that microinjection of glutamate into VNM significantly decrease the C4-C5 respiratory rate from 8,42±0,68 min-1 to 2,68 circa 0,32 min-1 (p<0,001). In this period the duration of the discharge in C4-C5 increased to 9,3 % (p<0,05) of the control level. In most of the cases (70%), microinjection of glutamate into VNM produced depression of respiratory rhythm generation. The latency period of this reactions was average 5-10 s. The spontaneous activity in the C4-C5 ventral root returned 4,1 min (range 30 s-22 min) after the onset of the respiratory depression. The amplitude of the discharge in C4-C5 was not significantly changed or decreased during VNM glutamatergic stimulation.
CONCLUSIONS: In the present study, we found that glutamatergic chemical stimulation of the rostral part VNM neurons in the newborn rat evokes decrease or full depression the spontaneous firing rate in the C4-C5 ventral root. Opposite in the adult rat glutamate acting on NMDA receptors of the vestibular subnuclei appears to contribute to the excitatory component of the vestibulo-respiratory responses (Xu F, et al., 2002). These vestibulo-respiratory reactions are dependent on the integrity of the medullary reticular formation (Mori RL, et al., 2001). We proposed that the inhibitory component of respiratory responses to activation of the glutamatergic system in the rostral part VNM can result first in there sinaptic organization and then in the particularity of synaptic transmission in the medullary reticular formation.
64 EFFECT OF PROLONGED BED REST ON THE VESTIBULOSYMPATHETIC REFLEX Ray, CA1; Dyckman, DJ1; Kearney, ML1; Meck, JV2 1Penn State College of Medicine; 2NASA Johnson Space Center
Postspaceflight orthostatic intolerance is associated with an inability to increase peripheral vascular resistance (PVR). Simulated microgravity (6° head-down bed rest, HDBR) studies have demonstrated inadequate increases in muscle sympathetic nerve activity (MSNA) in subjects that experience orthostatic intolerance during head-up tilt. Activation of the vestibulosympathetic reflex (VSR) using head-down rotation increases MSNA and PVR in humans. We tested the hypothesis that the VSR would be attenuated after approximately 35 days of HDBR. MSNA (microneurography) and leg blood flow (Doppler ultrasound of the popliteal artery) were measured before and after 36circa 1 days of HDBR in 7 subjects. Peripheral vascular conductance (PVC) was calculated by limb blood flow/mean arterial pressure. Before HDBR, HDR significantly increased MSNA (80circa25% bursts/min, 83circa 12% total activity; p<0.01) and tended to decrease PVC (13 circa 5%; p=0.09). After HDBR, the increase in MSNA elicited by HDR was attenuated compared to before HDBR. MSNA, burst frequency and total activity, increased only by 23circa13% and 34circa22% during HDR after HDBR, respectively. This result demonstrates a significant attenuation of the VSR after prolonged HDBR. Despite this decrease MSNA response, PVC did not change in response to the VSR after HDBR. These data provide support for the concept that attenuation of the VSR could contribute to an inadequate increase in MSNA observed post-HDBR in those subjects that experience orthostatic intolerance. Supported by NIH DC006459, HL077670, M01RR000073, NSBRI CA00404, and NAS9-97005
65 CONSEQUENCES OF THE DEVELOPMENT UNDER MODIFIED GRAVITY ON THE SETTING OF THE VESTIBULAR SENSORY NETWORK IN THE RAT Chabbert, Ch; Brugeaud, A; Gaboyard, S INSERM U583
Since the works of Hubel and Wiesel in the 70’s, it is widely admitted that the setting of the sensory neuronal network tightly depends on the quality of the sensory input during restricted periods of development. Any alteration of the primary stimulus during these critical phases has dramatic and irreversible consequences on the setting of the central neuronal connexions involved in the processing of the afferent sensory information (Hubel & Wiesel, 1970). Our research group is involved in the study of the impact of gravity on the setting and function of the vestibular system through a collaboration with the CNES for more than 10 years. In recent studies, we clearly demonstrated that variations of the gravity vector (hypergravity and microgravity) during mammal pre- and neo-natal developmental period, dramatically altered both the timing of the synaptogenesis within the utricular macula (Gaboyard et al. 2002; 2003) and the structure and function of the utricle hair cells (Chabbert et al. 2003a). A delay in setting synaptic contacts was also reported in birds upon development under microgravity (Dickman et al. 2003).
The aim of the present study was first to investigate further the consequences of the development under modified gravity on the synaptogenesis, by quantifying the delay in the synapse formation, and second to determine wether it affects axonal branching in the vestibular nuclei.
We recently reported that the transient expression of a voltage-gated ionic current (INa) brings to the neonate hair cells the ability to fire sodium-based action potentials and controls the activity-dependent secretion of BDNF in the utricles (Chabbert et al. 2003b). We also demonstrated that the down regulation of INa along the first postnatal week strictly depends on the setting of the synaptic contacts with the afferent terminals (Brugeaud et al. 2005). The expression of a large density of INa is a reliable marker of the synaptogenesis process in the utricle sensory cells. We therefore studied the developmental expression of INa in utricle hair cells from neonate rats raised under enhanced gravity (2G) conditions, using whole-cell patch-clamp recordings.
Preliminary results confirm that under enhanced gravity, the peak of INa expression is delayed by few days, since its down regulation did not occur before P6 (6 days after birth) instead of P3. In parallel, we undertook the study of central synaptic contacts using electron microscopy and immunocyochemistry against several synaptic proteins involved in the setting of functional synapses. This combined central and peripheral approaches should allow to determine the influence of the maturation of the peripheral synapses on the axonal branching in the vestibular nuclei. It should also indicate whether modifications of the gravity conditions during development might have consequences on the function of the vestibular system of mammals.
66 A NON DESTRUCTIVE MINIATURIZED METHOD OF IDENTIFICATION OF METABOLITES IN TISSUE karavolos, p; karavolos, A Schaller Engineering/NT Systems
INTRODUCTION This paper presents the results of an experiment which was designed to test the reliability of a device developed by NT Systems for the purpose of measuring the presence of calcium phosphate, potassium nitrate and hydrogen carbonate in tissue. The device uses a simple Teflon fiber woven in a cross pattern with a stitch density of about 1.2 denier, and is about 1 square cm and 4 mm thick. Each fiber is coated with a structurally complimentary biomarker or luminescent bacterial paste before it is woven into the pattern.
PURPOSE The objective of this experiment is to determine the effectiveness of two types of materials- structurally complementary biomarkers for calcium phosphate, potassium nitrate, hydrogen carbonate (calcium phosphates, Nitrate ATPase, Calcium Dehydrogenase) and a luminescent ligand molecule. Each was modeled using Accelrys and LDE programs. These compounds are found at or near the surface of hair folicle tissue.
METHODOLOGY The following materials were acquired from NT Systems, TriLink Inc, and Schaller Engineering Inc- 500 ml beakers, RC circuit, layouts, Teflon fibers, sewing apparatus, access to GC spectrometer and laboratory supplies, modeling software and the necessary biomarkers and bacterial pastes (Sigma Aldrich). Three sets of hair folicle tissues were scraped off of the epidermis of the skin near the anterior part of the knee. One set were controls with no biomarker or luminescent bacterial paste, but simply Teflon fibers soaked in distilled water, three were coated with the luminescent paste, and the other set of three were coated with the biomarker material. Lastly, each sample was collected using a steril cotton swab and analyzed for calcium phosphate, potassium nitrate and carbonates using conventional wet lab assay techniques and GC spectroscopic analysis. Both the biomarker and luminescent bacterial paste will conjugate with its structural compliment, generating a small potential on an electroactive wafer. In the case of the biomarker,this small potential is amplified using external electronics such as photomultipliers and amplifiers (Figure 1). In the case of the luminescent biomarker this potential is changed to a photon and is detected using an infrared diode and external electronics. Results The modeled results of the effort showed that the bacterial paste had the highest efficiency in detecting the compounds, by identifying 98.5% of the total material containing the above compounds, and the biomarker material identifying 95.4% of the total material. The controls (only the fiber material) only accounted for 0.003% of the total tissue material, and this is probably due to absorption of the compounds onto the fabric.
CONCLUSIONS Based on the initial results of the experiment, the bacterial paste (98.5%) is better suited for use for calcium phosphate, potassium nitrate and hydrogen carbonate identification than the biomarker material (95.4%).
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67 MEASURING AND ATTENUATING HEAD-MOVEMENT INDUCED OSCILLOPSIA Sanderson, J1; Kalsey, J1; Oman, CM2; Harris, LR1 1York University; 2Massachusetts Institute of Technology
Head movement contingent oscillopsia is commonly reported by astronauts during entry, landing, and for several days post flight, but methods for directly quantifying it have been lacking. Oscillopsia is characterized by the sensation that objects in the visual field are moving. Here we use vestibular Coriolis stimulation as a model of head-movement contingent oscillopsia and measure its temporal duration by the method of cancellation. Subjects sat on a rotating platform facing a large computer display. The platform rotated at a constant rate of 30°/sec. Subjects closed their eyes and moved their heads into a start position, either to the side (left ear on left shoulder) or down (chin on chest). They held this position for 20 seconds. When instructed, subjects quickly moved their head to the upright position and opened their eyes. A display appeared consisting of a field of white dots on a black background moving as if they were painted on a sphere centred on the subject’s head and rotating about an axis corresponding to the induced oscillopsia (pitch when starting from nose down; roll when starting from left ear on left shoulder). Subjects attended to the rate of slowing of the dots and compared it with the induced motion they were feeling. They indicated whether the dots appeared to slow down more or less rapidly than their perceived self rotation. A PEST parameter estimation technique was utilized to establish the rate of slowing that matched the rate of decline of the perceived rotation. Each subject’s time constant of slowing was measured under four conditions: induced roll or pitch motion, in the presence or absence of a superimposed earth stable scene consisting of a horizon and stable dot field.
In the absence of a visible horizon the average time constant was 4.2 ± 1.3 sec. With the horizon present condition the time constant was significantly reduced to 2.7 ± 0.8 secs. No significant difference was found between time constants obtained around the roll and pitch axes.
This method can be used to test neurovestibular countermeasures to oscillopsia that may be used by astronauts to reduce or eliminate the time spent experiencing this disorienting phenomenon.
Supported by NASA Cooperative Agreement NCC9-58 with the National Space Biomedical Research Institute, the Canadian Space Agency, and grants from the Natural Sciences and Engineering Research Council of Canada to L.R. Harris.
68 MENTAL TRANSFORMATIONS OF BODIES AND BODY-PARTS IN MICROGRAVITY Grabherr, L1; Bach, S2; Indermaur, K3; Metzler, S4; Mast, FW1 1University of Lausanne; 2Memory Clinic Basel; 3University of Fribourg; 4University of Zurich
BACKGROUND: The aim of this experiment was to investigate the influence of gravity on the cognitive ability to mentally transform images of bodies and body-parts. Previous studies in microgravity showed that performance in a mental rotation task requiring the comparison of abstract 3D stimuli remained unchanged when compared to performance in 1g. Neuroimaging (fMRI) and TMS studies revealed that mental transformations of such objects activate distinct brain areas compared to mental transformations of bodies or body-parts. To our knowledge, no study has yet been conducted in microgravity with a task that requires the mental transformation of body parts. Neuroimaging studies revealed - at least partly - the activation of motor-related brain areas when subjects mentally rotate their body or parts of their body (e.g., feet, hands). Any actual physical movement has to take into account the force of gravity acting upon the body or body parts, thus, requiring the processing and updating of a gravitational representation. Motor execution and motor imagery partly rely on the same mechanisms, and, therefore, it needs to be tested whether the absence of gravitational information alters the problem solving process of a task that requires an imagined transformation of a body or a body-part. Due to the absence of gravity an influence on the mental rotation process of bodies and body-parts is expected.
METHODS: Six male subjects (aged between 31 and 49) took part in the 40. ESA parabolic flight campaign and performed a psychophysical task on board the Airbus 300 Zero-G. Each subject solved the task in microgravity during 14 parabolas, each parabola lasting for about 22 seconds. Control measurements were taken in 1g 1 day before the flight on ground and during normal steady flight after each parabola. The subjects had to make spatial judgments about line drawings of a schematic human figure with one arm outstretched (similar to the figures known as Ratcliff figures) and pictures of body parts (hands). The stimuli appeared on a head-mounted display in varying orientations in the picture plane (0, 90, 180, 270 deg), either in back view (back of the figure or back of the hand facing the subject) or in front view (front of the figure or palm facing the subject). The subjects had to judge which arm of the figure was outstretched (if the stimulus was a body) or whether the picture represents the left or the right hand (if the stimulus was a hand). In order to solve this problem the participants are required to imagine a transformation of either their own body or body part rotating into the depicted stimuli or else to rotate the stimuli. The subjects responded by pressing either the joystick in their right hand or the joystick in their left hand. Reaction time and error rate were measured. The head-mounted display covered the entire visual field and thus prevented the processing of visual cues from the surrounding. The subjects were floating freely in 0g secured only by a harness and loose straps. During 1g they were seated on the padded floor of the aircraft.
RESULTS: In microgravity, the subjects showed overall increased response times as well as increased error rates when compared to 1g for both types of stimuli. A 2 x 2 x 2 repeated measures ANOVA with the factors stimuli (bodies, body-parts), stimulus orientation (0°, 180°), and gravity level (0g, 1g) revealed that the effect of gravity level is significant for response times (F(1,4)=7.944; p<.05) as well as for error rates (F(1,4)=18.349; p<.05). One subject had to be excluded from the analysis because error rates in one condition (hands rotated 180°) were extremely high (0.846 in 0g and 0.971 in 1g). It took the five subjects significantly longer to process the stimuli and they made more errors during microgravity when compared to 1g (measured on board). There was no main effect of stimulus type, revealing that the two stimuli, bodies and body-parts, are processed with the same speed and accuracy. Interestingly, however, the factors stimuli and gravity level interacted, (F(1,4)=8.626; p<.05), suggesting that the body-part stimuli are affected more strongly in microgravity than the body figures in terms of increased response times. None of the other interaction effects were significant.
CONCLUSIONS: A task that requires the mental transformation of bodies or body-parts seems to become more difficult during microgravity. This is in contrast to previous studies showing no effect of microgravity on the mental rotation of abstract 3D-objects. The results are discussed with respect to neurovestibular aspects of cognitive performance in microgravity and accordingly the role of gravity information in higher-level cognitive tasks.
The research was funded by the Swiss National Science Foundation (Grant 611-066052) and by ESA.
69 THE ROLE OF VISUAL BACKGROUND ORIENTATION ON THE PERCEPTUAL UPRIGHT DURING PARABOLIC FLIGHT Dyde, RT; Jenkin, M; Jenkin, HL; Zacher, JE; Harris, LR York University
The perceptual upright (PU) -- the orientation in which an object is most easily and naturally recognized - can be modelled as a combination of the orientation of the body, the visual background, and gravity. PU can be assessed by identifying a character the identity of which depends on its orientation ('The subjective visual vertical and the perceptual upright', (in press), Experimental Brain Research). Under the reduced gravity condition of parabolic flight, asking subjects to indicate their perceived orientation by 'setting a line to the vertical' as, for example, defined by the direction a ball would fall, causes them to complain that they don't have a clear sense of which way things might fall in weightlessness. However since the PU can be assessed by asking subjects whether a character is a 'p'or a 'd', the task remains clear.
Using a small observer pool of six participants we measured the influence of the orientation of the visual background on the PU under the low gravity conditions obtained in parabolic flight. Observers were tested in the fronto-parallel plane under conditions where: gravity was irrelevant (when all stimuli were presented orthogonal to gravity, with the subject lying supine); gravity was reduced (during exposure to microgravity created during parabolic flight); or gravity was increased (during the hyper- gravity phase of parabolic flight). When supine in 1g the influence of the background on the PU was reliably greater than when the observer was upright in 1g suggesting a relative increase in the effect of vision on PU in the absence of gravity. However in actual microgravity the influence of the background on PU was reliably less than in the equivalent 1g state; curiously a similar reduction relative to the 1g condition was also found during the hyper-gravity phase of parabolic flight. These perceptual changes are consistent with an increase in the use of the body as a reference frame when gravity is changed but they also suggest that the effects of microgravity cannot be simulated by simply arranging gravity to be orthogonal to that plane through lying supine.
Supported by NASA Cooperative Agreement NCC9-58 with the National Space Biomedical Research Institute, the Canadian Space Agency, and grants from the Natural Sciences and Engineering Research Council of Canada to L.R. Harris and M. Jenkin
70 TILT AND TRANSLATION MOTION PERCEPTION DURING PITCH TILT WITH VISUAL SURROUND TRANSLATION O' Sullivan, BM; Harm, DL; Reschke, MF; Wood, SJ NASA JSC
BACKGROUND: The central nervous system must resolve the ambiguity of inertial motion sensory cues in order to derive an accurate representation of spatial orientation. Previous studies suggest that multi-sensory integration is critical for discriminating linear accelerations arising from tilt and translation head motion. Visual input is especially important at low frequencies where canal input is declining. The NASA Tilt Translation Device (TTD) was designed to recreate post-flight orientation disturbances by exposing subjects to matching tilt self motion with conflicting visual surround translation. Previous studies have demonstrated that brief exposures to pitch tilt with fore-aft visual surround translation produced changes in compensatory vertical eye movement responses, postural equilibrium, and motion sickness symptoms. Adaptation appeared greatest with visual scene motion leading (versus lagging) the tilt motion, and the adaptation time constant appeared to be approximately 30 min.
METHODS: The purpose of this study was to compare motion perception when the visual surround translation was in-phase versus out-of-phase with pitch tilt. The in-phase stimulus presented visual surround motion one would experience if the linear acceleration was due to fore-aft self translation within a stationary surround, while the out-of-phase stimulus had the visual scene motion leading the tilt by 90 deg as previously used. The tilt stimuli in these conditions were asymmetrical, ranging from an upright orientation to 10 deg pitch back. Another objective of the study was to compare motion perception with the in-phase stimulus when the tilts were asymmetrical relative to upright (0 to 10 deg back) versus symmetrical (10 deg forward to 10 deg back). Twelve subjects (6M, 6F, 22-55 yrs) were tested during 3 sessions separated by at least one week. During each of the three sessions (out-of-phase asymmetrical, in-phase asymmetrical, in-phase symmetrical), subjects were exposed to visual surround translation synchronized with pitch tilt at 0.1 Hz for a total of 30 min. Tilt and translation motion perception was obtained from verbal reports and a joystick mounted on a linear stage. Horizontal vergence and vertical eye movements were obtained with a binocular video system. Responses were also obtained during darkness before and following 15 min and 30 min of visual surround translation.
RESULTS: Each of the three stimulus conditions involving visual surround translation elicited a significantly reduced sense of perceived tilt and strong linear vection (perceived translation) compared to pre-exposure tilt stimuli in darkness. This increase in perceived translation with reduction in tilt perception was also present in darkness following 15 and 30 min exposures, provided the tilt stimuli were not interrupted. Although not significant, there was a trend for the in-phase asymmetrical stimulus to elicit a stronger sense of both translation and tilt than the out-of-phase asymmetrical stimulus. Surprisingly, the in-phase asymmetrical stimulus also tended to elicit a stronger sense of peak-to-peak translation than the in-phase symmetrical stimulus, even though the range of linear acceleration during the symmetrical stimulus was twice that of the asymmetrical stimulus.
CONCLUSIONS: These results are consistent with the hypothesis that the central nervous system resolves the ambiguity of inertial motion sensory cues by integrating inputs from visual, vestibular, and somatosensory systems.
ACKNOWLEDGEMENTS: This research was supported by National Space Biomedical Research Institute through NASA NCC 9-58 (NA 0405) and FAS Science Challenge, Ireland.
71 SENSORY DISORIENTATION IN SPACE HABITATS - A CHALLENGE FOR SPACEARCHITECTS AND SPACE PSYCHOLOGISTS. Jorgensen, Jesper SpaceArch
Coming long-term space missions will challenge both the designs of technology and the human factors. The paucity of sensory inputs from the outside environment can be expected to pose challenges to crews on longduration missions in the confines of spacecraft. A history of research and practice has demonstrated that sensory deprivation or exposure to confusing sensory inputs affect individuals, both in their performance of tasks and their well-being. Therefore, space design and architecture should take this into consideration when designing for future missions.
Microgravity and the normal organization of sensory input as experienced on Earth are challenges to those living and working in space. Individuals can overcome some effects of the confused or conflicted sensory system with increased tolerance or awareness of these difficulties. Sensory systems most affected by microgravity relate to spatial orientation and vestibular systems. These systems combine stimuli from at least four different sensory sources, which present the possibility for conflicting perception. Within a continuum of human variation, individuals, given the same sensory stimuli, may react differently.
Some of the problems of sensory deprivation or conflicting sensory inputs in space crews can be simulated and investigated on Earth in simulations in extreme environments. On the background of experiences and results from both space physiological research and simulations, key results can be incorporated in the design process.
The paper will discuss how knowledge from space physiology can be used as a tool in design for future and present space habitats, demonstratet in both research and the development of space architectural designs. Fokus will be laid on comming long-term interplanetary missions.
The paper will advocate for a closer integration of space medicine, space physiology, space psychology and space architecture in this processes, as a definite step to highen the quality of future mission analysis and development.
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73 THE USE OF DYNAMIC VISUAL ACUITY AS A FUNCTIONAL TEST OF GAZE STABILIZATION FOLLOWING SPACE FLIGHT Peters, BT1; Mulavara, AP2; Brady, R3; Miller, CA3; Richards, JT3; Warren, LE4; Cohen, HS5; Bloomberg, JJ6 1Wyle Laboratories, Inc.; 2National Space Biomedical Research Institute, Baylor College of Medicine; 3Wyle Laboratories, Inc., Neuroscience Laboratory; 4Universities Space Research Association; 5Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine; 6Neuroscience Laboratories, NASA-Johnson Space Center
Background: After prolonged exposure to a given gravitational environment the transition to another is accompanied by adaptations in the sensorimotor subsystems, including the vestibular system. Variation in the adaptation time course of these subsystems, and the functional redundancies that exist between them make it difficult to accurately assess the functional capacity and physical limitations of astro/cosmonauts using tests on individual subsystems. While isolated tests of subsystem performance may be the only means to address where interventions are required, direct measures of performance may be more suitable for assessing the operational consequences of incomplete adaptation to changes in the gravitational environment.
Methods: A test of dynamic visual acuity (DVA) is currently being used in the JSC Neurosciences Laboratory as part of a series of measures to assess the efficacy of a countermeasure to mitigate postflight locomotor dysfunction. In the current protocol, the subject's visual acuity is determined using Landolt ring optotypes presented sequentially on a computer display. Visual acuity assessments are made both while standing and while walking at 1.8 m/s on a motorized treadmill. The use of a psychophysical threshold detection algorithm reduces the required number of optotype presentations and the results can be presented immediately after the test. The difference between the walking and standing acuity measures provides a metric of the change in the subject’s ability to maintain gaze fixation on the visual target while walking. This functional consequence is observable regardless of the underlying subsystem most responsible for the change.
Results: Data from 15 cosmo/astronauts have been collected following long-duration (~6 months) stays in space using a visual target viewing distance of 4.0 meters. An investigation of the group mean shows a change in DVA soon after the flight that asymptotes back to baseline approximately one week following their return to earth. The performance of some subjects nicely parallels the stereotypical recovery curve observed in the group mean data. Others show dramatic changes in DVA from one test day to another. These changes may be indicative of a re-adaptation process that is not characterized by a steady improvement with the passage of time, but is instead a dynamic search for appropriate coordinative strategy to achieve the desired gaze stabilization goal.
Discussion: Ground-based data have been collected in our lab using DVA with one of the goals being to improve the DVA test itself. In one of these studies, the DVA test was repeated using a visual target viewing distance of 0.5 meters. While walking, the relative contributions of the otoliths and semi- circular canals that are required to stabilize gaze are affected by visual target viewing distance. It may be possible to exploit this using the current treadmill DVA test to differentially assess changes in these vestibular subsystems. The postflight DVA evaluations currently used have been augmented to include the so-called near target version of the test. Preliminary results from these assessments, as well as the results from the ground-based tests will also be reported.
DVA provides a direct measure of a subject's ability to see clearly in the presence of self-motion. The use of the current tests for providing a functionally relevant metric is evident. However, it is possible to expand the scope of DVA testing to include scenarios other than walking. A facility for measuring DVA in the presence of passive movements is being created. Using a mechanized platform to provide the perturbation, it should be possible to simulate aircraft and automobile vibration profiles. Used in conjunction with the ''far''and ''near'' visual displays this facility should be able to assess a subject's ability to clearly see distant objects as well as those that appear on the dashboard or instrument control panel during functionally relevant situations.
This work supported by the National Space Biomedical Research Institute through NASA NCC 9-58 and by NASA ISS Experiment E120. 74 DEVELOPMENT OF TESTING METHODOLOGIES TO EVALUATE POSTFLIGHT LOCOMOTOR PERFORMANCE Mulavara, AP1; Peters, BT2; Cohen, HS3; Richards, JT2; Miller, CA2; Brady, R2; Warren, LE4; Kozlovskaya, IB5; Bloomberg, JJ6 1National Space Biomedical Research Institute, Baylor College of Medicine, Houston, TX; 2Wyle Laboratories, Houston, TX; 3Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, BCM, Houston, TX; 4Universities Space Research Association Division of Space Life Sciences, Houston, TX; 5Institute for Biomedical Problems, Moscow; 6NASA-Johnson Space Center, Houston, TX
Crewmembers experience locomotor and postural instabilities during ambulation on Earth following their return from space flight. Gait training programs designed to facilitate recovery of locomotor function following a transition to a gravitational environment need to be accompanied by relevant assessment methodologies to evaluate their efficacy. The goal of this paper is to demonstrate the operational validity of two tests of locomotor function that were used to evaluate performance after long duration space flight missions on the International Space Station (ISS).
METHODS: Sixteen cosmo/astronauts were tested before (3 sessions) and after (postflight days 1, 2, 4, 7, 25) long- duration missions (6 months) on the ISS. Locomotor performance was assessed before and after space flight using two tests of gait function. The Integrated Treadmill Locomotion Test characterized alterations in the integrated function of multiple sensorimotor sub-systems. This test called for subjects to walk on a motorized treadmill while we measured changes in visual acuity, dynamic postural stability, and head-trunk kinematics. The Functional Mobility Test provided a corresponding assessment of a subject's ability to perform challenging locomotor maneuvers similar to those encountered during typical activities of daily living and especially those encountered during an egress from a space vehicle.
INTEGRATED TREADMILL LOCOMOTION TEST (ITLT) Subjects walked at 6.4 km/h on a motorized treadmill while performing a visual acuity test. Each trial lasted approximately 30 seconds and was repeated four times. The visual test consisted of identifying the position of the gap in a Landholt ''C'' that was presented centrally on a laptop computer positioned 4 meters in front at eye level. The movement of different segments of the body was measured using a video-based motion measurement system. Six time synchronized CCD cameras, sampling at 60 Hz, were used to obtain the three dimensional positions of light weight retro-reflective markers placed on the various body segments.
Data from eight subjects who performed the ITLT 1 day after their return were further analyzed. Six degree of freedom motions of the head and torso were calculated using the three dimensional trajectories of three markers placed on each of the segments. For each 30-second trial head and torso angular roll, pitch, and yaw orientations with respect to space were subjected to Fourier analysis, and the maximum amplitude of these signals at their predominant frequency was calculated. The average and 95% confidence interval (CI) of each variable was determined across the preflight and postflight trials collected on 1 day after their return to quantify and compare each subject’s head and torso movements.
FUNCTIONAL MOBILITY TEST (FMT) The FMT required subjects to step over and duck under foam obstacles along with walking through a series of pylons set up on a 6.0 m X 4.0 m obstacle course. Subjects walked at a preferred pace through the obstacle course set up on a base of 10 cm thick medium density foam. The foam provided an unstable surface that increased the challenge of the test by making subjects less reliant on somatosensory cues. Subjects were instructed to walk through the course as fast but as safely as possible without touching any of the objects on the course. This task was repeated three times each in the clockwise and the counterclockwise directions. The time to complete the course (TCC) data from all 16 subjects for each postflight day were averaged and collated for further analysis. A logarithmic curve using a least squares procedure was fit through these points and its intersection with the average circa 95% confidence interval of the mean preflight TCC across all subjects was calculated to determine the duration of time taken to recover functional locomotor performance.
75 RESULTS After space flight, 6/8 subjects (75%) showed a significant change in both the head and torso roll and pitch angular movement magnitudes, while 2/8 (25%) and 4/8 (50%) subjects showed a significant change in the head and torso yaw movement magnitudes, respectively, during treadmill walking. These results show that changes in head and torso movements are more frequent in the pitch and roll planes as compared to the yaw plane.
Results from FMT of the 16 subjects indicate that the adaptation to space flight led to a significant increase in time to traverse the obstacle course and recovery of function took an average of 13.6 days after their return.
CONCLUSION Results from the ITLT indicate that both head and torso movements during locomotion show postflight changes predominantly in the pitch and roll planes presumably due to the central reinterpretation of otolith information. Importantly, these alterations in head and torso control are accompanied by compromised functional mobility.
This work supported by the National Space Biomedical Research Institute through NASA NCC 9-58 and by NASA ISS Experiment E120.
76 DEVELOPMENT OF A COUNTERMEASURE TO MITIGATE POSTFLIGHT LOCOMOTOR DYSFUNCTION Bloomberg, JJ1; Mulavara, AP2; Peters, BT3; Cohen, HS4; Richards, JT3; Miller, CA3; Brady, R3; Warren, LE5; Ruttley, TM1; Kozlovskaya, IB6 1NASA-Johnson Space Center, Houston, TX; 2National Space Biomedical Research Institute, Baylor College of Medicine, Houston, TX; 3Wyle Laboratories, Houston, TX; 4Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, BCM, Houston, TX; 5Universities Space Research Association Division of Space Life Sciences, Houston, TX; 6Institute of Biomedical Problems, Moscow
Astronauts returning from space flight experience locomotor dysfunction following their return to Earth. Our laboratory is currently developing a gait adaptability training program that is designed to facilitate recovery of locomotor function following a return to a gravitational environment. The training program exploits the ability of the sensorimotor system to generalize from exposure to multiple adaptive challenges during training so that the gait control system essentially ''learns to learn'' and therefore can reorganize more rapidly when faced with a novel adaptive challenge.
Evidence for the potential efficacy of an adaptive generalization gait training program can be obtained from numerous studies in the motor learning literature which have demonstrated that systematically varying the conditions of training enhances the ability of the performer to learn and retain a novel motor task. These variable practice training approaches have been used in applied contexts to improve motor skills required in a number of different sports.
The central nervous system (CNS) can produce voluntary movement in an almost infinite number of ways. For example, locomotion can be achieved with many different combinations of joint angles, muscle activation patterns and forces. The CNS can exploit these degrees of freedom to enhance motor response adaptability during periods of adaptive flux like that encountered during a change in gravitational environment. Ultimately, the functional goal of an adaptive generalization countermeasure is not necessarily to immediately return movement patterns back to ''normal''. Rather the training regimen should facilitate the reorganization of available sensory and motor sub-systems to achieve safe and effective locomotion as soon as possible after long duration space flight. Indeed, this approach has been proposed as a basic feature underlying effective neurological rehabilitation.
We have previously confirmed that subjects participating in an adaptive generalization training program using a variety of visuomotor distortions and throwing as the dependent measure can learn to enhance their ability to adapt to a novel sensorimotor environment (Roller et al., 2001). Importantly, this increased adaptability was retained even one month after completion of the training period. Adaptive generalization has been observed in a variety of other tasks requiring sensorimotor transformations including manual control tasks and reaching (Bock et al., 2001, Seidler, 2003) and obstacle avoidance during walking (Lam and Dietz, 2004).
Taken together, the evidence suggests that a training regimen exposing crewmembers to variation in locomotor conditions, with repeated transitions among states, may enhance their ability to learn how to reassemble appropriate locomotor patterns upon return from microgravity. We believe exposure to this type of training will extend crewmembers’ locomotor behavioral repertoires, facilitating the return of functional mobility after long duration space flight. In other words, our proposed training protocol will compel subjects to develop new behavioral solutions under varying sensorimotor demands. Over time subjects will learn to create appropriate locomotor solution more rapidly enabling acquisition of mobility sooner after long-duration space flight.
A gait adaptability training program can be superimposed on nominal treadmill exercise activities thus ensuring that no additional crew time is required to perform this type of training regimen and that it can be implemented with current in-flight exercise systems available on the International Space Station. During treadmill walking subjects can be exposed to variations in visual flow, body loading, stability in the walking surface along with alterations in task constraints (reading, head movements). These variations will systematically and repeatedly challenge the gait control system during treadmill walking, enhancing sensorimotor flexibility, ultimately facilitating adaptation and re-adaptation to different gravitational environments.
77 Our laboratory is currently developing adaptive generalization training procedures and the associated flight hardware to implement such a training program during regular in-flight treadmill operations. A visual display system will provide variation in visual flow patterns during treadmill exercise. Crewmembers will be exposed to a virtual scene that can translate and rotate in six-degrees-of freedom during their regular treadmill exercise period. Associated ground based studies are focused on determining optimal combinations of sensory manipulations (visual flow, body loading and support surface variation) and training schedules that will produce the greatest potential for adaptive flexibility in gait function during exposure to challenging and novel environments. An overview of our progress in these areas will be presented at the meeting.
This work supported by the National Space Biomedical Research Institute through NASA NCC 9-58 and by NASA ISS Experiment E120.
78 DEVELOPMENT OF IN-FLIGHT COUNTERMEASURES WITH MULTIMODAL EFFECTS - MUSCLE STRENGTH AND BALANCE FUNCTION Oddsson, LIE1; Bloomberg, JJ2; Zemkova, E3; Dwyer, A4; Chow, A4; Meyer, PF5; Wall, C6 1Boston University; 2NASA/Johnson Space Center, Houston; 3Faculty of Physical Education and Sports, Comenius University, Bratislava; 4Department of Biomedical Engineering, Boston University; 5Tyco Healthcare; 6Massachusetts, Eye and Ear Infirmary/Harvard Medical School, Boston
BACKGROUND: Astronauts lose postural control, coordination and muscle strength as well as bone mass and cardiovascular capacity during exposure to microgravity. These problems may influence safety during orbit entry and egress of the vehicle after landing, on Earth or during future missions to the Moon and Mars. Furthermore, astronauts have post-flight balance related problems during activities such as standing, walking and turning corners that may jeopardize potential mission activities on the Moon and Mars surfaces. Nevertheless, current in-flight countermeasures have not included exercises for postural control. Devices currently used in the International Space Station use a harness and bungee cords to strap down the subject bilaterally to provide a stabilizing load that may eliminate the need for balance control. An altered strapping technique may allow exercises that combine strength and balance training effects and we propose to demonstrate this possibility using an on-earth model of frontal plane microgravity effects on the balance control system. By the use of a 90 degree tilted room, we can match both the frontal plane dynamics of the task and the frontal plane inputs to the vestibular system (semicircular canals and otolith organs) to those occurring in microgravity. For frontal plane balancing tasks, the tilted room environment provides motion stimuli sensed by the vestibular system that are similar to those experienced in microgravity. We have demonstrated that mediolateral balance training conducted in the 90 deg tilted visual environment, with the subject strapped to a freely moving device providing a longitudinal G-like load through a weight and pulley system, can improve balance function during upright standing. In the current project we use the tilted room environment to investigate whether strength and balance function can be improved in parallel, potentially improving the efficiency of in-flight countermeasures.
METHODS: To date, two groups of 12 healthy young subjects have trained in the tilted room environment over a period of four weeks, four sessions/week. The two groups have performed the same task (“squat”) in the tilted room environment with the same load and progression although the first group perform the squat on a balance board to add an element of balance requirement to the task. The second group performed the squat without balance requirement while attached to a set of linear rails. The program was progressive (50%-75% of 1RM) and each session consisted of 6 sets of 10 reps. Pre- and post-testing of muscle strength and balance function is performed. Maximal Voluntary Contraction (MVC) and maximal power during isokinetic squat extension (10 deg/s & 35 deg/s) was measured using a computerized exercise system (Ariel Life Systems, CES). Test of balance function is performed and Center of Pressure (COP) is sampled at 100Hz using a moveable balance platform (BALDER) during upright stance tasks of increasing level of difficulty; 1-2) Stationary stance on two legs, eyes open and closed; 3-4) Stationary stance on one leg, eyes open and closed; 5-6) Continuous horizontal perturbation, two legs, eyes open and closed. Ten trials of 30s were performed under each condition. Subjects were instructed to stand as still as possible during each trial. Summary statistics and Stabilogram-Diffusion parameters were extracted from the COP data.
RESULTS AND CONCLUSIONS: Results of the Strength+Balance group and partial results from the Strength only group are reported here. The MVC and power production during both slow and fast isokinetic squat extension movements improved significantly (12%-20%) for both groups and did not appear to be different between the groups. Changes were seen in balance parameters during one-legged standing for the Strength+Balance group. Under open eyes conditions there was a 40% increase in mediolateral short-term stochastic activity (p<0.012). Under eyes closed conditions there was a 105 ms decrease in mediolateral critical time (p<0.05) indicating that, on average, postural corrections were implemented faster after training. A similar, although non-significant, decrease was seen with eyes open (p<0.14). Training appeared to alter the relationship between balance behavior under eyes closed vs. eyes open. The Critical Displacement parameter, indicating the average COP displacement at which the postural control process becomes predominantly antipersistent, was five times higher under eyes closed compared to eyes open pre-training and decreased significantly post-training. A similar decrease was seen for the ratio between short-term diffusion coefficients indicating a relatively lower short-term stochastic activity under eyes closed conditions as a result of the training. This may indicate an
79 improved use of somatosensory as well as visual cues for balance control as a result of the training. Findings to date support the view that it should be possible to combine in-flight strength training with balance training to improve and/or maintain both strength and balance function.
80 ASSESSMENT OF POSTFLIGHT LOCOMOTOR PERFORMANCE UTILIZING A TEST OF FUNCTIONAL MOBILITY: STRATEGIC AND ADAPTIVE RESPONSES Warren, LE1; Mulavara, AP2; Peters, BT3; Cohen, HS4; Richards, JT3; Miller, CA3; Brady, R3; Ruttley, TM5; Bloomberg, JJ5 1Universities Space Research Association; 2National Space Biomedical Research Institute, Baylor College of Medicine; 3Wyle Laboratories; 4Bobby R. Alford Department of Otorhinolaryngology and Communicative Sciences, Baylor College of Medicine; 5Neuroscience Laboratories, NASA-Johnson Space Center
Space flight induces adaptive modification in sensorimotor function, allowing crewmembers to operate in the unique microgravity environment. This adaptive state, however, is inappropriate for a terrestrial environment. During a re-adaptation period upon their return to Earth, crewmembers experience alterations in sensorimotor function that cause various disturbances in perception, spatial orientation, posture, gait, and eye-head coordination. This sensorimotor dysfunction could prevent or extend the time required to make an emergency egress from the vehicle, thus compromising crew safety and mission objectives.
We are investigating two types of motor learning that may interact with each other and influence a crewmember's ability to re-adapt to Earth's gravity environment. The first is strategic learning, in which crewmembers make rapid modifications in their motor control strategy emphasizing error reduction. This type of learning may be critical during the first minutes and hours after landing. The second is adaptive learning, in which long-term plastic transformations occur. This may involve morphological changes and synaptic modification. Recently, these two behavioral components have been associated with separate brain structures that control the execution of motor strategies: the strategic component was linked to the posterior parietal cortex and the adaptive component was linked to the cerebellum (Pisella, et al. 2004). The goal of this paper is to demonstrate the relative contributions of the strategic and adaptive components to the re-adaptation process in locomotor control after long duration space flight missions on the International Space Station (ISS).
The Functional Mobility Test (FMT) was developed to assess crewmembers’ locomotor ability postflight from an operational and functional perspective. Sixteen crewmembers were tested preflight (3 sessions) and postflight (days 1, 2, 4, 7, 25) following a long duration space flight (more than 6 months) on the ISS. We have further analyzed the FMT data to characterize strategic and adaptive components during the postflight re-adaptation period.
Crewmembers walked at a preferred pace through an obstacle course set up on a base of 10cm thick medium density foam (Sunmate Foam, Dynamic Systems, Inc., Leicester, NC). The 6.0m X 4.0m course consisted of the following obstacles: several foam pylons arranged in a so-called slalom fashion; a 46cm high foam hurdle; and a so-called portal constructed of two successive 31cm high Styrofoam blocks, with a horizontal bar foam bar between them, which was adjusted to the height of the crewmember’s shoulders. The portal required crewmembers to bend at the waist while stepping over the barriers. Crewmembers were instructed to walk through the course as quickly and as safely as possible without touching any of the objects on the course. This task was performed three times in the clockwise direction and three times in the counterclockwise direction in a randomized order. The dependent measures for each trial were time to complete the course (seconds) and the number of obstacles contacted.
For each crewmember, the time to complete each FMT trial from postflight days 1, 2, 4, 7 and 25 was analyzed. A single logarithmic curve using a least squares calculation was fit through these data as a whole to produce a single comprehensive marco curve. This macro curve, composed of data spanning 25 days, illustrates the re-adaptive learning function over the longer time scale. Additionally, logarithmic curves were fit to the 6 data trials within each individual postflight test day to produce 5 separate daily curves. These micro curves, produced from data obtained over the course of minutes, illustrate the strategic learning function exhibited over the shorter time scale.
The macro curve for all crewmembers exhibited adaptive motor learning patterns over the 25 day recovery period. Additionally, 9/16 crewmembers exhibited significant strategic motor learning patterns in their micro curves, as defined by mag(m) > 1 in the equation of the line y=m*LN(x) +b.
81 These data indicate that postflight recovery in locomotor function involves both strategic and adaptive mechanisms. Future countermeasures will be designed to enhance both recovery processes.
This work supported by the National Space Biomedical Research Institute through NASA NCC 9-58 and by NASA ISS Experiment E120.
82 RELATIVE CONTRIBUTIONS OF STRATEGIC AND ADAPTIVE CONTROL MECHANISMS IN PLASTIC RECALIBRATION OF LOCOMOTION Richards, JT1; Mulavara, AP2; Ruttley, TM3; Peters, BT1; Warren, LE4; Bloomberg, JJ3 1Wyle Laboratories, Inc.; 2National Space Biomedical Research Institute; 3NASA Johnson Space Center; 4Universities Space Research Association
Following space flight astronauts experience gait and postural instabilities due to inflight adaptive alterations in sensorimotor function. The training regimen we are developing is based on the concept of adaptive generalization. We anticipate that this training will accelerate readaptation to gravitational environments (e.g., Earth, Moon and Mars) following space flight. Adaptation to sensory discordances results from the contributions of two distinct mechanisms: strategic modification vs. adaptive realignment. The strategic behavioral component has been linked to the posterior parietal cortex, while the adaptive component was associated with the cerebellum, in motor strategy execution (Pisella, et al. 2004). Our adaptive generalization training model uses both strategic and adaptive modifications in motor control to facilitate transition from one sensorimotor state to another. Strategic modification represents immediate and transitory modifications in control that are employed to deal with short-term changes in the prevailing environment. If these changes are prolonged then plastic adaptive changes are evoked that modify central nervous system function to automate new behavioral responses. We have shown previously that exposure to rotating visual scenes during treadmill walking induced strategic (Richards, et al., 2003) and plastic adaptive changes (Mulavara, et al., 2005) in locomotor function. The goal of the present study was to investigate the relationship between these two types of motor learning mechanisms to further refine our adaptive generalization paradigms.
METHODS-- Subjects (n = 10) walked on a motorized linear treadmill while viewing a wide field-of- view virtual scene for 24 minutes. The scene was static for the first 4 minutes and then, for the last 20 minutes, depicted constant rate self-motion equivalent to walking around the perimeter of a room to one’s left. During treadmill walking, subjects’ three-dimensional torso positions and angles were recorded at 60 Hz, and gait cycle timing data were collected at 1000 Hz. Before and after the treadmill locomotion adaptation period, subjects performed five stepping trials where, in each trial, they marched in place at 90 steps/min for a total of 100 steps while blindfolded in a quiet room. At the end of each stepping trial, the subject’s final heading direction was measured relative to his or her initial heading direction. Subjects never received post-test feedback of their performance and final heading direction.To characterize the positional (X, Y and Z) and angular (roll, pitch and yaw) variation of the torso movements over the 20-min treadmill locomotion period, we calculated the root mean square (RMS) and sum of standard deviations (SSD) variation, respectively, for every 10 second bin of kinematic data collected. Normalized variability data were then calculated for each subject as the ratios, Rp and Ro, of RMS and SSD values during scene rotation to that during static scene presentation, respectively. Finally, means (RP and RO) and 95% confidence intervals (CIP and CIO) of the RP and RO were calculated over groups of six adjacent 10-second bins. RP and RO data were a measure of the stability of torso movement during scene motion. CIP and CIO data were a measure of variations in this torso movement stability during scene motion. We completed separate regression analyses on each parameter for each subject. To investigate whether a relationship existed between the observed change in heading direction following adaptation and the rate at which the stability of torso movements and its variation changed during the adaptation process, Pearson correlation tests were used with heading direction differences and regression fit slopes as variables.RESULTS-- Regression analyses showed that decreasing trends over the 20-min adaptation period were significant, only for the CIP and the RO of torso X and Yaw movements, respectively. Pearson correlation tests further showed a significant negative correlation between the heading direction bias observed during post-adaptation stepping trials and the rate at which the CIP for torso X movements decreased (p < 0.05). The negative correlation between the heading direction bias and the rate at which the RO for torso Yaw movements decreased was marginally significant (p = 0.06).
CONCLUSIONS-- Results indicate that there is a relationship between the rate at which strategic modification is reduced and the depth of plastic adaptive change in locomotor heading trajectory produced after prolonged viewing of a rotating virtual scene during treadmill walking. Therefore, countermeasure training programs designed to enhance sensorimotor adaptability need to harness both strategic and adaptive mechanisms to produce both rapid alterations in behavior followed by consolidation of these changes into an adaptive response requiring less overall cognitive supervision.
This work supported by the National Space Biomedical Research Institute through NASA NCC 9-58. 83 DEPENDENCE OF MOTION SICKNESS SUSCEPTIBILITY ON THE TIME CONSTANT OF THE ANGULAR VESTIBULO-OCULAR REFLEX (AVOR) Dai, MJ1; Raphan, T2; Cohen, B3 1Mount Sinai School of Medicine; 2Department of Computer and Information Science, Brooklyn College, CUNY, Brooklyn, NY; 3Department of Neurology, Mount Sinai School of Medicine, NY
We studied motion sickness (MS) elicited by rolling the head while rotating (RWR) in 16 normal subjects (S¡¯s). There was a strong positive relation between the aVOR time constant (Tc) and motion sickness susceptibility (MSS). As the aVOR Tc became shorter with repeated testing, S¡¯s became less susceptible to MS. The high frequency gain of the aVOR had no relationship to MSS in these S¡¯s. This indicates MSS is related to the process in the central vestibular system that produces the dominant Tc of the aVOR, which we have called ¡®velocity storage¡¯.
This process enhances the low frequency response of the aVOR and orients eye velocity to gravity or to gravito-inertial acceleration. We further investigated this relationship by employing baclofen, a GABAB agonist. Baclofen reduced the aVOR Tc and the coupling gain to velocity storage in 6 S¡¯s, but had no effect on the high frequency aVOR gain. We then tested the MSS of 7 normal S¡¯s after baclofen and a placebo using RWR. The S¡¯s were less susceptible to MS after baclofen than after receiving a placebo. They were also less susceptible after baclofen than the 16 normal S¡¯s previously tested with RWR. The changes in Tc due to baclofen or to habituation support the idea that reduction of the aVOR Tc reduces MSS.
To verify that the high frequency aVOR pathway plays no role in setting the level of MSS, we tested 5 bilateral vestibular deficit patients who had a normal high frequency aVOR gains but very short aVOR Tc¡¯s. All of these patients had substantially less MSS than normal S¡¯s. We conclude that velocity storage, not the high frequency component of the aVOR, is involved in the production of MS. We further postulate that MSS can be reduced by any method that shortens the time constant of velocity storage.
Sponsored by NSBRI NA00406, DC005204, DC05222, and EY01867.
84 THE DISTRIBUTION OF OTOLITH POLARIZATION VECTORS BASED ON THE CURVATURE OF MACULAR SURFACES IN MAMMALS Kondrachuk, AV1; Jaeger, R2; Haslwanter, T3 1Institute of Physics, Natl.Acad.of Sci.; 2Dept. of Astrophysics, University of Tuebingen; 3Up. Austr.Res, Dept. for Med.Inf. Linz,Austria & Inst. of Theor.Physics, ETH Zurich
PURPOSE The function of an otolith as a gravisensor comprises a sequence of different physical and chemical processes whose experimental investigation is difficult or unfeasible. To understand the relationship between the input and output in an otolith organ, certain assumptions have to be formulated. The classic works of Fernandez and Goldberg (1976) and Goldberg et al. (1990) were devoted to measurements of unit neural responses corresponding to static forces (gravity and centrifugal force), recorded from otoliths of squirrel monkeys., The following main assumptions have been used in these investigations, although some of them were not expressed explicitly. 1) The directional sensitivity of afferent unit can be characterized by a single polarization vector (functional vector), which reflects a cumulative reaction of hair cells that belong to the terminal field of afferent. 2) The functional vector is lying in tangent plane to the macular surface in the terminal field. 3) The functional vector is specific characteristic of the given terminal field and does not depend on the type of the mechanical stimulation of otolith. 4) An afferent response is determined by the projection of the vector of the head acceleration on the functional vector. The analysis of the otolith membrane morphology, afferent responses and the results of the modeling show that the listed assumptions are not obvious and need to be carefully analyzed. The main purpose of the present work is to check if spatial distribution of the directions of functional vectors agrees with the basic assumption that functional vectors are lying in tangent planes to terminal fields. We also reconstructed morphological vectors (Lindeman,1969) as 3D vectors and analyzed the correlation of their spatial distribution with functional vectors. Since the data were obtained from different species, the work cannot be considered as quantitative proof of the link between functional and morphological vectors and macular topology, but rather as a preliminary probe into their relationships.
METHODS To reconstruct 3D macular surfaces, the data of Takagi&Sando (1988) were used. While it is commonly assumed that epithelia surfaces are smooth, the measurement process can introduce geometric artifacts that change considerably over a short distance, and the measured surfaces look “bumpy”. The data sets were pre-processed to remove artifacts from the measurement process and make macular surface smooth. The remaining artifacts of a slicing procedure were removed by smoothing the surfaces with a Savitzky-Golay filter. The hypothesis tested in the work is that the directions of functional vectors are lying in the planes that are tangent to the corresponding macular surface in the regions of terminal fields. Since we consider macular surface to be smooth, the tangent planes and normal vectors can be built at every point of this surface. The functional vectors were normalized to the unit length. The distribution of tips of these unit vectors (corresponding to all possible orientations of functional vectors lying in tangent planes to macular surface) on the unit sphere will divide the surface of the unit sphere in two parts: admissible and non-admissible for the directions of functional vectors-tangents to 3D macular surface. The shapes of these parts and their location on the sphere will reflect the spatial relief of the macular surface. The tips of unit vectors corresponding to Goldberg’s 3D functional vectors can easily be projected on the unit sphere. The same procedure can be applied to unit vectors corresponding to 3D morphological polarization vectors reconstructed from Lindeman’s data.
RESULTS AND CONCLUSIONS. The results of the modeling do not contradict the basic assumption tested that the functional vectors are tangent to the macular surface: all projections of the functional vectors from (Goldberg et al, 1990) lie within the limits of an “admissible zone” determined by the spatial relief of epithelium. The modeling showed that although the curvature of the utricular macular surface is relatively small (the radius of the curvature> the size of the macula), the tips of corresponding unit vectors may cover more than 2/3 of unit sphere provided that the functional vectors are tangent to the macular surface. In the case of a saccular surface, the ends of unit vectors may cover about 1/3 of unit sphere. The
85 distribution of the directions of reconstructed 3D morphological vectors correlates with the distribution of functional vectors.
This study was supported by the Betty and David Koetser Foundation for Brain Research, by DLR 50WB9940, and by the REGINS project.
86 ULTRASTRUCTURAL AND CONFOCAL STUDY OF VESTIBULAR HAIR CELLS FROM THE TILTED MOUSE. Gaboyard-Niay, S; Price, SD; Lysakowski, A University of Illinois at Chicago
One goal of studies in sensory systems is to determine whether appropriate stimuli affect the structure and function of sensory organs. As has often been found in the visual system (Hubel and Wiesel, 1970), both the morphology and physiology of the central nervous system (CNS) depend on sensory input during a critical period of development. However, in the peripheral organs themselves, the existence of such a critical period is still debated. Two different ways to study the relation between a stimulus and its sensory receptor organ are hyperstimulation and sensory deprivation.
For the utricular maculae, ground-based hypergravity experiments correspond to hyperstimulation of hair cells. Unfortunately, sensory deprivation cannot be performed on the ground, and so “space” experiments are required to investigate the loss of stimulus. Under hypergravity conditions, different experiments in rodents raised during the embryological and postnatal period strongly support the idea of a critical period for the proper development of these vestibular end-organs as well. The size of otolithic crystals is modified (Sondag et al., 1997), the apical cross-sectional area of hair cells appears to be larger (Wubbels et al., 2002), large changes occur in the membrane permeability of hair cells (Chabbert et al., 2003), and synaptogenesis is delayed during the first postnatal week (Gaboyard et al., 2003). In weightlessness, such developmental studies have been limited in mammals because of the problems associated with nursing pups in spaceflight. Indeed, studies that have been undertaken during the embryonic period (Bruce and Fritzsch, 1997) or during late postnatal development (Dememes et al., 2001; Raymond et al., 2000), did not show modification of the vestibular endorgans. In contrast, experiments on quails subjected to weightlessness during their entire period of development did show alterations of the vestibular sensory epithelia. The otoconial mass and the number of synaptic ribbons in type I hair cells increased, and calyx development was delayed (Dickman et al., 2003).
These data strongly suggest that sensory deprivation during a precise period of development alters the function of utricular maculae. Thus, if a precise critical period does exist in mammals, no study in weightlessness has yet been performed during this time. The tilted mouse provides a model of weightlessness on Earth since the maculae lack otoconia (Lane, 1986, 1987). These adult tilted mice do not display a global morphological alteration of the macular sensory epithelium, but they have no afferent response or vestibular behavior (Ornitz et al., 1998, Jones et al., 2004). However, a study of the afferent innervation during development also demonstrated an alteration during the first postnatal week, since the number of afferent neurons was reduced (Smith et al., 2003). Thus, these tilted mice, as a wonderful ground-based model for vestibular studies, may also provide an indication of the influence of critical period stimuli that would occur during the first postnatal week of rats and mice.
Using immunohistochemistry, confocal imaging and electron microscopy, we first tried to determine if depriving hair cells of stimulation during development can lead to the production of the necessary molecular machinery of synaptic transmission. We investigated the ultrastructure of their typical synaptic ribbons in utricular and saccular hair cells, and different proteins, linked to the hair cell function, as calretinin, Rab3, RIM1. So far, we have found an increased number of type II hair cells expressing calretinin in comparison to wild type mice. This might reflect a slight dis-regulation or an adaptation of the maturation process of hair cells. More quantification and more time points are needed in tilted mice to define whether these crucial modifications affect hair cell function or if sensory deprivation merely induces minor alterations that can be later compensated. This would provide some insight about the risks of developing organisms in space, and then answer the question: ''does development of the utricular primary receptor in a ''weightless'' environment induce a ''molecular'' disturbance that could definitely impair hair cell function?'' (from NSBRI's research announcements: Neurovestibular Adaptation Strategic Plan). Supported by the NSBRI through NASA NCC 9-58.
87 NATIONAL SPACE BIOMEDICAL RESEARCH INSTITUTE EDUCATION AND OUTREACH Rahmati Clayton, S1; Thomson, WA1; MacLeish, MY2; Moreno, NP1 1Baylor College of Medicine; 2Morehouse School of Medicine
BACKGROUND The NSBRI Education and Outreach Team aims to communicate the significance of space life sciences, and to transfer and disseminate knowledge gained via the biomedical advances made by NSBRI Research Teams to students across the educational continuum, from kindergarten through postdoctoral level, as well as teachers and general public. This aim is being achieved through development of education and training programs designed to target the next generation of explorers, engineers, and space flight scientists.
METHODS AND RESULTS Translating and Transferring NSBRI Research Curriculum Development. Seven instructional guides were developed, tested and disseminated. Six additional guides are under development. Guides were disseminated to more than 32,000 teachers, representing more than four million students (estimated at 130 students per secondary school teacher). Teacher Professional Development. More than 15,000 teachers participated in NSBRI Education and Outreach Program initiatives and activities, including summer research programs for high school teachers, workshops at national conferences of science teacher and professional organizations, local teacher workshops, and intensive one-year teacher internships.
PROMOTING CAREERS IN SPACE LIFE SCIENCE Direct Student Contact. More than 3,400 students participated in Education and Outreach projects. Enhancing University Teaching and Learning. Graduate and Undergraduate Courses. Two courses—“Space Biomedical Research†and “Sensorimotor Adaptation†—were offered to 50 graduate and undergraduate students at MIT, University of Maryland, and Smith College.
ENHANCING CAREER PATHWAYS JSC Summer Internship Program includes 10- to 15-week learning opportunities for 34 undergraduates and 18 graduate and professional students in NASA, JSC, or NSBRI laboratories. Begun in 2004, the Postdoctoral Fellowship is a two-year program that includes workshops, presentations, and a one-week JSC experience. 2004-2006 Fellows: Sophie Gaboyard, PhD, University of Illinois; Andrew Judge, PhD, Boston University; Vesna Zderic, PhD, University of Washington; Luis Cardoso Landa, PhD, Mt. Sinai School of Medicine (Dr. Landa has accepted a faculty position at City College of New York). 2005-2007 Fellows: Hirofumi Aoki, PhD, Massachusetts Institute of Technology; Philipp Oberdoerffer, PhD, Harvard Medical School; Amy Ouellette, PhD, Stanford University. The Irish Internship Program was initiated in October 2005 and is supported by Foras Aiseanna Saothair (Training and Employment Authority of Ireland). It is a companion to the Florida Space Authority Irish Internship Program. There are 20 Interns in Florida and Texas (at Rice, UTHSC-Houston, BCM, NASA and NSBRI), and the program will be expanding to the Boston area. Promoting Understanding of NSBRI in Science, Education, and Medical Communities Dissemination of NSBRI information and findings via website, print media, televised broadcasts has included 21 peer-reviewed papers and presentations and 55 presentations at national and regional meetings. NSBRI Continuing Medical Education Program activities included 39 events for a total of 820 participants through JSC Physician Grand Rounds and Lecture Series, and Aerospace Medicine Board.
REACHING OUT TO THE PUBLIC Collaboration with museums and science centers included Barany Chair and Knowledge Station exhibits, as well as Family and teacher activities. NSBRI materials were disseminated to the following national institutions: Challenger Learning Centers, Fernbank Science Center (Atlanta, GA), Space Center Houston, Children’s Museum of Houston, Denver Museum of Nature and Science, Space Science Institute, MIT Learning Laboratory, Boston Museum of Science, and Peabody Essex Museum.
NEW STRATEGIES FOR DISSEMINATION Collaboration with NASA CONNECT™ and NASA SCIFiles™ to create television programs based on NSBRI Education and Outreach materials reached 130 PBS stations, with a possible audience of 75 million viewers. Web-Based Resources have been the new strategy to reach broader audiences. A model for online teacher professional development can we viewed on BCM’s www.bioedonline.org website. Additional curriculum materials are available on NSBRI and individual program websites at Baylor College of Medicine, MIT, Morehouse School of Medicine, and Mt. Sinai School of Medicine.
88 CONCLUSIONS Through research and evaluation, NSBRI’s Education and Outreach team is studying the impact of its activities on: teacher knowledge and practice; student learning outcomes and attitudes; the effectiveness of web-based educational strategies in comparison to traditional methods; the success of NSBRI education and outreach efforts in addressing the needs and challenges of students, teachers, schools, and communities.
This work supported by the National Space Biomedical Research Institute through NASA NCC 9-58
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