Marquette University e-Publications@Marquette Master's Theses (2009 -) Dissertations, Theses, and Professional Projects EEG Source Localization of Visual and Proprioceptive Error Processing During Visually- Guided Target Tracking with the Wrist Prajakta Sukerkar Marquette University Recommended Citation Sukerkar, Prajakta, "EEG Source Localization of Visual and Proprioceptive Error Processing During Visually-Guided Target Tracking with the Wrist" (2010). Master's Theses (2009 -). Paper 70. http://epublications.marquette.edu/theses_open/70 EEG SOURCE LOCALIZATION OF VISUAL AND PROPRIOCEPTIVE ERROR PROCESSING DURING VISUALLY-GUIDED TARGET TRACKING WITH THE WRIST by Prajakta Ashok Sukerkar, B.S. A Thesis submitted to the Faculty of the Graduate School, Marquette University, in Partial Fulfillment of the Requirements for the Degree of Master of Science Milwaukee, Wisconsin December 2010 ABSTRACT EEG SOURCE LOCALIZATION OF VISUAL AND PROPRIOCEPTIVE ERROR PROCESSING DURING VISUALLY-GUIDED TARGET TRACKING WITH THE WRIST Prajakta A. Sukerkar, B.S. Department of Biomedical Engineering Master of Science Sensorimotor error feedback plays an integral role in movement; it adapts the sensorimotor control system to rapid changes in environmental loads and allows smooth limb coordination. Studies have shown the cerebellum, parietal, and premotor cortices to be involved in error processing, but the specific neural function of those areas remain relatively unknown. The objective of this study was to characterize the neural sources that underlie the computation of visual and proprioceptive error during goal-directed movement. We tested the hypothesis that the cortical networks meditating the two sensory error systems are distinct. Subjects (n=7) used a cursor to track a moving target presented on a computer display. Cursor position on the screen was yoked to a 1-D wrist manipulandum that recorded wrist position, velocity, and torque and applied controlled torques to the wrist. External displacement errors were applied as either force perturbations to the wrist (Proprioceptive condition) or visual displacements to cursor position (Visual condition). Five levels of displacement were applied to identify neural responses that co-varied with the magnitude of displacement. EEG was collected from 64 electrodes. Distributed cortical source modeling (Brainstorm v.3) identified cortical sources that contributed to the averaged EEG activity across error levels. In force perturbation trials, current source density across subjects showed early somatosensory, premotor, motor, and frontal activity ranging from 43±5 ms to 48±6 ms, followed by parietal activity at 70±8 ms. In visual perturbation trials, parietal activation at 113±8 ms was followed by sensory, motor, and premotor activation (123±42 ms to 131±22 ms). Spatial analyses suggest error representations for proprioception and vision may be computed in spatially distinct areas of frontal and parietal cortices. The temporal sequence of error-related activity suggests that sensorimotor error may not initially be computed in parietal regions before being processed in motor areas. The early premotor/motor activation in the Proprioceptive condition suggests that a course estimate of error is first computed in those areas before a more accurate representation of error is generated in the parietal regions. This may occur to initiate a course correction faster in the direction of the error while gathering more information about the error. i DEDICATION To all teachers of the past, present, and future Yatah sarvani bhutani pratibhanti stithani cha yatrai vo pasamam yanti tasmai satyatmane namah Salutations to that reality in which all the elements, and all the animate and inanimate beings shine as if they have an independent existence, and in which they exist for a time and into which they merge. ‘Vasistha’s Yoga’. by Swami Venkatesananda, State University of New York Press, Albany, NY ii ACKNOWLEDGEMENTS I would like to thank my parents for their unending support and unconditional love. A special note of gratitude to my father for pushing me headfirst into graduate school – this journey has undoubtedly been one of the most rewarding experiences of my life. A huge hug to my sister, Kavita, who never turned down an opportunity to help me with my endless Matlab questions, and for always encouraging me to stay strong and push through whenever I had fleeting thoughts of renouncing everything and absconding to the Himalayas. I would like to acknowledge and thank my advisor, Dr. Scott Beardsley, whose knowledge, ethics, and support have been a true motivation throughout my thesis. His strive for nothing short of perfection and professionalism has helped me improve as a researcher. I would also like to extend my gratitude to my committee members, Drs. Robert Scheidt and Brian Schmit, for graciously allowing me to use their lab resources and equipment and for offering their invaluable feedback on my thesis project. A note of recognition also to Drs. Sylvain Baillet and Aniko Szabo for getting me acquainted with the necessary skill set to perform the analyses outlined in my thesis, and a big ‘thank you’ to the Falk Family Medical Research Trust and the Department of Biomedical Engineering at Marquette University for their financial support of this project. My thesis would have been much less enjoyable had it not been for the help of my many friends at Marquette University. I would especially like to thank my labmate, Chintan, and friends, Madhavi, Ashvini, Nuttaon, Krishnaj, Sanket, Ryan, Sunaina (& UCSB), Sheraz, Sampada, Tushar, David, Megan, and Jain, for all their help and support. My love and gratitude goes out to my friends in the Art of Living for being my loving family in the United States. Special thanks to Naresh, Shraddha, and Parneet. Last and in no way least, I would like to express a heart full of gratitude to my spiritual advisor, friend, and mentor, Sri Sri Ravi Shankar, for making me grow leaps and bounds as a person, for giving me an opportunity to give back to the society, and for making my life magical and beautiful – Jai Guru Dev! iii TABLE OF CONTENTS DEDICATION ................................................................................................................................. i ACKNOWLEDGEMENTS ............................................................................................................ ii LIST OF FIGURES ........................................................................................................................ v LIST OF TABLES ......................................................................................................................... vi LIST OF ABBREVIATIONS ....................................................................................................... vii 1 INTRODUCTION AND SPECIFIC AIMS ............................................................................ 1 2 BACKGROUND & SIGNIFICANCE .................................................................................... 3 2.1 Motivation ..................................................................................................................................... 3 2.2 Types of Sensory Error ................................................................................................................. 4 2.3 Brain Areas Involved in Sensorimotor Error Processing .............................................................. 5 2.3.1 The Posterior Parietal Cortex ................................................................................................ 5 2.3.2 The Cerebellum ................................................................................................................... 11 2.3.3 The Premotor, Motor, and Medial-Frontal Cortices ........................................................... 12 2.4 Event Related Potentials in Sensory Error Processing: the N100, P300, and fERN ................... 14 2.5 Visual and Proprioceptive Sensorimotor Processing .................................................................. 16 2.6 Significance ................................................................................................................................. 17 3 METHODS ............................................................................................................................ 19 3.1 Overview ..................................................................................................................................... 19 3.2 Experimental Apparatus .............................................................................................................. 19 3.3 Subjects ....................................................................................................................................... 21 3.4 Experimental Design ................................................................................................................... 21 3.4.1 Trial Structure ..................................................................................................................... 22 3.4.2 Proprioceptive Trials ........................................................................................................... 23 3.4.3 Visual Trials ........................................................................................................................ 24 iv 3.4.4 Triggering ........................................................................................................................... 26 3.5 Experimental