DOCSLIB.ORG

Visual Pathways

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

VISUAL PATHWAYS Valentin Dragoi Department of Neurobiology and Anatomy Parallel streams of visual processing Outline • Visual pathways: From retina to the cortex • Information ppgrocessing in visual cortex Outline • Visual pathways: From retina to the cortex • Information ppgrocessing in visual cortex VISUAL PATHWAY Retinal ggganglion cell axons leave the eye at the optic disc The retinal ganglion axons exit the eye to form the optic nerve. VISUAL PATHWAY OPTIC NERVE Consists of 3° afferent axons Axons of retinal ganglion cells OPTIC CHIASM Optifibiiific nerve fibers originating from the nasal retina that decussate in the optic chiasm Optic nerve fibers originating from the temporal retina do not decussate in the optic chiasm OPTIC TRACT Consists of 3° afferent axons from the nasal half of the contralateral eye & the temporal half of the ipsilateral eye RETINAL GANGLION CELL AXONS: OPTIC TRACT Optic Optic nerve tract Optic Hypothalamus: chiasm regulation of cidihthircadian rhythms Lateral geniculate nucleus Pretectum: reflex contlftrol of pup il and lens Optic radiation Superior colliculus: orienting the movements of head and eyes Striate cortex LATERAL GENICULATE NUCLEUS OF THE THALAMUS The visual system thalamic nucleus LGN MGN LGN organized into 6 cell layers 2 Magnocellular layers 4 Parvocellular layers with thin layers of kinocellular (dust-like) neurons interposed All LGN neurons • are monocular - respond to stimulation of one eye only • have concentric (ON/OFF or OFF/ON) receptive fields Type mLGN neurons in LGN magnocellular layers • synapse with Type M retinal ganglion axons • have large concentric receptive fields • are insensitive to color • sensitive to small changes in brightness levels (scotopic vision) • are rapidly-adapting (motion sensitive) Type pLGN neurons in LGN parvocellular layers • synapse with Type P retinal ganglion axons • have small concentric recepti ve fields ( high acuity ) • are sensitive to color (color sensitivity) • are not sensitive to small changes in brightness levels • are slowly-adapting (indicate the duration stimulus is “on”) Outline • Visual pathways: From retina to the cortex • Information ppgrocessing in visual cortex PRIMARY VISUAL CORTEX Primary visual cortex Calcarine fissure Cerebral cortex is differentiated into 6 horizontal layers COLOR SELECTIVITY SPECIALIZED PROCESSING : CHARACTERISTICS OF V1 BLOB (COLOR ) CELLS •coliilor sensitive - target ofkf kLGN axons • small concentric receptive fields • monocular - onlyyy one eye stimulates the blob cells • indifferent to stimulus orientation • indifferent to stimulus movement (slowly-adapting) BLOBS RETINA …. …. Striate cortex: V1 V1 BLOB CELL RESPONSES Orientation selectivity Stimulus Stimulus orientation presented Light b ar sti mul us projected on screen Recording from visual cortex Record 01 23 Time (sec) ORIENTATION SELECTIVITY SPECIALIZED PROCESSING : COMMON CHARACTERISTICS OF INTERBLOB CELLS •eldifildlongated receptive fields • insensitive to color • binocular w/ ocular dominance > one eye elicits a stronger response • most are sensitive to stimulus orientation > strongest response to particular orientation …. …. Interblob cells ORIENTATION SELECTIVITY SPECIALIZED PROCESSING : SHAPE/FORM & LOCATION V1 INTERBLOB CELLS •eldifildlongated receptive fields • insensitive to color • binocular w/ ocular dominance > one eye elicits a stronger response • sensitive to stimulus orientation > strongest response to particular orientation •insensitive to movement - target of pLGN axons > slowly-adapting response • location specific > stronggpest response in field center DIRECTION OF MOTION SPECIALIZED PROCESSING : MOTION SENSITIVE V1 INTERBLOB CELLS •eldifildlongated receptive fields • insensitive to color • binocular w/ ocular dominance > one eye elicits a stronger response • sensitive to stimulus orientation > strongest response to particular orientation • sensitive to MOVEMENT => target of mLGN axons DIRECTION OF MOTION SPECIALIZED PROCESSING : MOTION+LOCATION SENSITIVE V1 INTERBLOB CELLS •eldifildlongated receptive fields • insensitive to color • binocular w/ ocular dominance > one eye elicits a stronger response • sensitive to stimulus orientation > strongest response to particular orientation • most sensitive to motion => target of mLGN axons •some location specific DIRECTION OF MOTION SPECIALIZED PROCESSING : MOTION DIRECTION SENSITIVE V1 INTERBLOB CELLS •eldifildlongated receptive fields • insensitive to color • binocular w/ ocular dominance > one eye elicits a stronger response • sensitive to stimulus orientation > strongest response to particular orientation • most sensitive to motion - => target of mLGN axons •others direction specific ‘Ice-cube’ model of primary visual cortex R L R L R L R L functional domains Optical imagingof Single conditionmaps Orientationmap Cortical vasculature domains Stimulus computer Camera Li g ht g uide Amplifier Video data acquisition EXTRA-STRIATE AND ASSOCIATION AREAS NON-HUMAN PRIMATES VISUAL CORTICAL AREAS Posterior parietal lobe Middle & Medial Superior Temporal gyrus Striate (Visual) cortex Extrastriate cortex Inferior temporal gyrus HIGHER ORDER PROCESSING V1 SENDS MOST OF ITS AXONS TO EXTRASTRIATE CORTEX EXTRASTRIATE CORTEX (V2, V3 & V4) SEND AXONS TO ASSOCIATION CORTEX (TEMPORAL & PARIETAL AREAS) DORSAL STREAM: > SUPERIOR TEMPORAL & PARIETAL NECESSARY FOR •spatial orientation • binocular fusion • depth perception • spatial location • movement detection “THE WHERE” HIGHER ORDER PROCESSING V1 SENDS MOST OF ITS AXONS TO EXTRASTRIATE CORTEX EXTRASTRIATE CORTEX (V2, V3 & V4) SEND AXONS TO ASSOCIATION CORTEX (TEMPORAL & PARIETAL AREAS) VENTRAL STREAM: > INFERIOR “TEMPORAL” GYRUS IMPORTANT FOR SHAPE & COLOR • perception • discrimination • recognition • memory • learning “THE WHAT” Motion processing Shape processing in infero-temporal (IT) cortex Parallel streams of visual processing Spatial vision Lesion to MT abolishes the perception of motion X without affecting object Object vision vision X Lesion to V4 abolishes color vision without affecting spatial vision Suggested readings 1. Neuroscience book (Purves et al.), Chapter 12.
Recommended publications
  • Structure and Function of Visual Area MT

    Structure and Function of Visual Area MT

    AR245-NE28-07 ARI 16 March 2005 1:3 V I E E W R S First published online as a Review in Advance on March 17, 2005 I E N C N A D V A Structure and Function of Visual Area MT Richard T. Born1 and David C. Bradley2 1Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115-5701; email: [email protected] 2Department of Psychology, University of Chicago, Chicago, Illinois 60637; email: [email protected] Annu. Rev. Neurosci. Key Words 2005. 28:157–89 extrastriate, motion perception, center-surround antagonism, doi: 10.1146/ magnocellular, structure-from-motion, aperture problem by HARVARD COLLEGE on 04/14/05. For personal use only. annurev.neuro.26.041002.131052 Copyright c 2005 by Abstract Annual Reviews. All rights reserved The small visual area known as MT or V5 has played a major role in 0147-006X/05/0721- our understanding of the primate cerebral cortex. This area has been 0157$20.00 historically important in the concept of cortical processing streams and the idea that different visual areas constitute highly specialized Annu. Rev. Neurosci. 0.0:${article.fPage}-${article.lPage}. Downloaded from arjournals.annualreviews.org representations of visual information. MT has also proven to be a fer- tile culture dish—full of direction- and disparity-selective neurons— exploited by many labs to study the neural circuits underlying com- putations of motion and depth and to examine the relationship be- tween neural activity and perception. Here we attempt a synthetic overview of the rich literature on MT with the goal of answering the question, What does MT do? www.annualreviews.org · Structure and Function of Area MT 157 AR245-NE28-07 ARI 16 March 2005 1:3 pathway.
  • Neuroanatomy Crash Course

    Neuroanatomy Crash Course

    Neuroanatomy Crash Course Jens Vikse ∙ Bendik Myhre ∙ Danielle Mellis Nilsson ∙ Karoline Hanevik Illustrated by: Peder Olai Skjeflo Holman ​ Second edition October 2015 The autonomic nervous system ● Division of the autonomic nervous system …………....……………………………..………….…………... 2 ● Effects of parasympathetic and sympathetic stimulation…………………………...……...……………….. 2 ● Parasympathetic ganglia ……………………………………………………………...…………....………….. 4 Cranial nerves ● Cranial nerve reflexes ………………………………………………………………….…………..…………... 7 ● Olfactory nerve (CN I) ………………………………………………………………….…………..…………... 7 ● Optic nerve (CN II) ……………………………………………………………………..…………...………….. 7 ● Pupillary light reflex …………………………………………………………………….…………...………….. 7 ● Visual field defects ……………………………………………...................................…………..………….. 8 ● Eye dynamics …………………………………………………………………………...…………...………….. 8 ● Oculomotor nerve (CN III) ……………………………………………………………...…………..………….. 9 ● Trochlear nerve (CN IV) ………………………………………………………………..…………..………….. 9 ● Trigeminal nerve (CN V) ……………………………………………………................…………..………….. 9 ● Abducens nerve (CN VI) ………………………………………………………………..…………..………….. 9 ● Facial nerve (CN VII) …………………………………………………………………...…………..………….. 10 ● Vestibulocochlear nerve (CN VIII) …………………………………………………….…………...…………. 10 ● Glossopharyngeal nerve (CN IX) …………………………………………….……….…………...………….. 10 ● Vagus nerve (CN X) …………………………………………………………..………..…………...………….. 10 ● Accessory nerve (CN XI) ……………………………………………………...………..…………..………….. 11 ● Hypoglossal nerve (CN XII) …………………………………………………..………..…………...………….
  • Quantitative Analysis of Axon Collaterals of Single Pyramidal Cells

    Quantitative Analysis of Axon Collaterals of Single Pyramidal Cells

    Yang et al. BMC Neurosci (2017) 18:25 DOI 10.1186/s12868-017-0342-7 BMC Neuroscience RESEARCH ARTICLE Open Access Quantitative analysis of axon collaterals of single pyramidal cells of the anterior piriform cortex of the guinea pig Junli Yang1,2*, Gerhard Litscher1,3* , Zhongren Sun1*, Qiang Tang1, Kiyoshi Kishi2, Satoko Oda2, Masaaki Takayanagi2, Zemin Sheng1,4, Yang Liu1, Wenhai Guo1, Ting Zhang1, Lu Wang1,3, Ingrid Gaischek3, Daniela Litscher3, Irmgard Th. Lippe5 and Masaru Kuroda2 Abstract Background: The role of the piriform cortex (PC) in olfactory information processing remains largely unknown. The anterior part of the piriform cortex (APC) has been the focus of cortical-level studies of olfactory coding, and asso- ciative processes have attracted considerable attention as an important part in odor discrimination and olfactory information processing. Associational connections of pyramidal cells in the guinea pig APC were studied by direct visualization of axons stained and quantitatively analyzed by intracellular biocytin injection in vivo. Results: The observations illustrated that axon collaterals of the individual cells were widely and spatially distrib- uted within the PC, and sometimes also showed a long associational projection to the olfactory bulb (OB). The data showed that long associational axons were both rostrally and caudally directed throughout the PC, and the intrinsic associational fibers of pyramidal cells in the APC are omnidirectional connections in the PC. Within the PC, associa- tional axons typically followed rather linear trajectories and irregular bouton distributions. Quantitative data of the axon collaterals of two pyramidal cells in the APC showed that the average length of axonal collaterals was 101 mm, out of which 79 mm (78% of total length) were distributed in the PC.
  • Visual Cortex in Humans 251

    Visual Cortex in Humans 251

    Author's personal copy Visual Cortex in Humans 251 Visual Cortex in Humans B A Wandell, S O Dumoulin, and A A Brewer, using fMRI, and we discuss the main features of the Stanford University, Stanford, CA, USA V1 map. We then summarize the positions and proper- ties of ten additional visual field maps. This represents ã 2009 Elsevier Ltd. All rights reserved. our current understanding of human visual field maps, although this remains an active field of investigation, with more maps likely to be discovered. Finally, we Human visua l cortex comprises 4–6 billion neurons that are organ ized into more than a dozen distinct describe theories about the functional purpose and functional areas. These areas include the gray matter organizing principles of these maps. in the occi pital lobe and extend into the temporal and parietal lobes . The locations of these areas in the The Size and Location of Human Visual intact human cortex can be identified by measuring Cortex visual field maps. The neurons within these areas have a variety of different stimulus response proper- The entirety of human cortex occupies a surface area 2 ties. We descr ibe how to measure these visual field on the order of 1000 cm and ranges between 2 and maps, their locations, and their overall organization. 4 mm in thickness. Each cubic millimeter of cortex contains approximately 50 000 neurons so that neo- We then consider how information about patterns, objects, color s, and motion is analyzed and repre- cortex in the two hemispheres contain on the order of sented in these maps.
  • Structural Brain Abnormalities in Patients with Primary Open-Angle Glaucoma: a Study with 3T MR Imaging

    Structural Brain Abnormalities in Patients with Primary Open-Angle Glaucoma: a Study with 3T MR Imaging

    Glaucoma Structural Brain Abnormalities in Patients with Primary Open-Angle Glaucoma: A Study with 3T MR Imaging Wei W. Chen,1–3 Ningli Wang,1,3 Suping Cai,3,4 Zhijia Fang,5 Man Yu,2 Qizhu Wu,5 Li Tang,2 Bo Guo,2 Yuliang Feng,2 Jost B. Jonas,6 Xiaoming Chen,2 Xuyang Liu,3,4 and Qiyong Gong5 PURPOSE. We examined changes of the central nervous system CONCLUSIONS. In patients with POAG, three-dimensional MRI in patients with advanced primary open-angle glaucoma revealed widespread abnormalities in the central nervous (POAG). system beyond the visual cortex. (Invest Ophthalmol Vis Sci. 2013;54:545–554) DOI:10.1167/iovs.12-9893 METHODS. The clinical observational study included 15 patients with bilateral advanced POAG and 15 healthy normal control subjects, matched for age and sex with the study group. Retinal rimary open angle glaucoma (POAG) has been defined nerve fiber layer (RNFL) thickness was measured by optical formerly by intraocular morphologic changes, such as coherence tomography (OCT). Using a 3-dimensional magne- P progressive retinal ganglion cell loss and defects in the retinal tization-prepared rapid gradient-echo sequence (3D–MP-RAGE) nerve fiber layer (RNFL), and by corresponding psychophysical of magnetic resonance imaging (MRI) and optimized voxel- abnormalities, such as visual field loss.1 Recent studies by based morphometry (VBM), we measured the cross-sectional various researchers, however, have suggested that the entire area of the optic nerve and optic chiasm, and the gray matter visual pathway may be involved in glaucoma.2–23 Findings from volume of the brain.
  • Network Centrality in Patients with Acute Unilateral Open Globe Injury: a Voxel‑Wise Degree Centrality Study

    Network Centrality in Patients with Acute Unilateral Open Globe Injury: a Voxel‑Wise Degree Centrality Study

    MOLECULAR MEDICINE REPORTS 16: 8295-8300, 2017 Network centrality in patients with acute unilateral open globe injury: A voxel‑wise degree centrality study HUA WANG1, TING CHEN1, LEI YE2, QI-CHEN YANG3, RONG WEI2, YING ZHANG2, NAN JIANG2 and YI SHAO1,2 1Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, Hunan 410008; 2Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Jiangxi Province Clinical Ophthalmology Institute and Oculopathy Research Centre, Nanchang, Jiangxi 330006; 3Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Xiamen, Fujian 361102, P.R. China Received January 12, 2017; Accepted August 1, 2017 DOI: 10.3892/mmr.2017.7635 Abstract. The present study aimed to investigate functional Introduction networks underlying brain-activity alterations in patients with acute unilateral open globe injury (OGI) and associations with Open globe injury (OGI) is a severe eye disease that frequently their clinical features using the voxel-wise degree centrality causes unilateral visual loss. Ocular trauma is a public health (DC) method. In total, 18 patients with acute OGI (16 males and problem in developing countries (1,2). A previous study indicated 2 females), and 18 healthy subjects (16 males and 2 females), that the annual prevalence of ocular trauma was 4.9 per 100,000 closely matched in age, sex and education, participated in the in the Western Sicily Mediterranean area, which investigated a present study. Each subject underwent a resting-state functional 5 year period from January 2001 to December 2005 (3). In addi- magnetic resonance imaging scan. The DC method was used tion, the incidence of OGI is increased in men compared with to assess local features of spontaneous brain activity.
  • Isolated Relative Afferent Pupillary Defect Secondary to Contralateral Midbrain Compression

    Isolated Relative Afferent Pupillary Defect Secondary to Contralateral Midbrain Compression

    OBSERVATION Isolated Relative Afferent Pupillary Defect Secondary to Contralateral Midbrain Compression Cheun Ju Chen, MD; Mia Scheufele, MD; Maushmi Sheth, MD; Amir Torabi, MD; Nick Hogan, MD, PhD; Elliot M. Frohman, MD, PhD Background: Relative afferent pupillary defects are typi- accounts for the relative afferent pupillary defect con- cally related to ipsilateral lesions within the anterior vi- tralateral to the described lesion. sual pathways. Result: Magnetic resonance imaging of the brain revealed a pineal tumor compressing the right rostral midbrain. Objective: To describe a patient who had a workup for headache and was found to have an isolated left relative Conclusion: While rare, a relative afferent pupillary de- afferent pupillary defect without any other neurological fect can occasionally occur secondary to lesions in the findings. postchiasmal pathways. In these circumstances, the pu- pillary defect will be observed to be contralateral to the Design: We review the neuroanatomy of the pupil- side of the lesion. lary light reflex pathway and emphasize the nasotem- poral bias of decussating fiber projections, which Arch Neurol. 2004;61:1451-1453 RELATIVE AFFERENT PUPIL- though retinal fibers concerned with this lary defect (RAPD) is char- reflex transmit information to both the ip- acterized by pupillary dila- silateral and contralateral midbrain, there tion upon illuminating the is a slight crossing bias, with about 53% of eye during the swinging the fibers crossing in the optic chiasm Aflashlight test. The presence of this sign sig- (chiefly derived from the nasal retina) and nifies an abnormality in the transmission 47% remaining ipsilateral. This anatomi- of light information within the pupillary cal organization of the pupillary constric- light constrictor pathway from the retina tor pathway results in the possibility of pro- to the rostral midbrain circuitry involved ducing an RAPD during illumination of the in this reflex.
  • Measurement of the Normal Optic Chiasm on Coronal MR Images

    Measurement of the Normal Optic Chiasm on Coronal MR Images

    Measurement of the Normal Optic Chiasm on Coronal MR Images Andrew L. Wagner, F. Reed Murtagh, Ken S. Hazlett, and John A. Arrington PURPOSE: To develop an objective method for measuring the optic chiasm and to document its normal range in size. METHODS: Measurements of the height and area of the optic chiasm, made on coronal T1-weighted MR images with the use of commercially available region-of-interest software, were obtained in 114 healthy subjects who had a total of 123 MR studies. A normal range and standard deviation were calculated, and the information was broken down by age and sex. RESULTS: The mean area of the optic chiasm was 43.7 mm2, with a standard deviation of 5.21. The mean width was 14.0 mm, with a standard deviation of 1.68. CONCLUSION: The area and width of the optic chiasm can be measured with the use of commercially available software, which allows an objective estimate of the chiasm’s size. Knowledge of the normal size range of the optic chiasm can be helpful in the early detection of some disorders. Index terms: Optic chiasm; Brain, anatomy; Brain, measurement AJNR Am J Neuroradiol 18:723–726, April 1997 The optic chiasm is an important land- months and that had been interpreted as normal. No pa- mark when interpreting magnetic resonance (MR) tient had suspected visual or endocrine abnormalities. All examinations of the brain. A small chiasm can be the examinations had been performed with a 1.5-T Gen- an indication of several disorders, the most com- eral Electric (Milwaukee, Wis) Signa or 1.5-T Siemens mon of which is septooptic dysplasia (1), and a (Cary, NC) Somatom MR system using routine imaging large chiasm can be the result of glioma, menin- protocols, with additional 3-mm T1-weighted contiguous coronal sections used for measurements.
  • Biorxives Gaze-Stabilization Pdf Creator

    Biorxives Gaze-Stabilization Pdf Creator

    bioRxiv preprint doi: https://doi.org/10.1101/2021.07.30.454479; this version posted August 1, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Visuo-vestibular gaze control – conserved subcortical processing Tobias Wibble1,2, Tony Pansell2, Sten Grillner1, Juan Pérez-Fernández1,3,* 1The Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden 2The Department of Clinical Neuroscience, Marianne Bernadotte Centrum, St: Erik’s Eye Hospital, Karolinska Institutet, Stockholm, Sweden 3CINBIO, Universidade de Vigo, Campus universitario Lagoas, Marcosende, 36310 Vigo, Spain *Corresponding author: [email protected] Abstract Gaze stabilization compensates for movements of the head or external environment to minimize image blurring, which is critical for visually-guided behaviors. Multisensory information is used to stabilize the visual scene on the retina via the vestibulo-ocular (VOR) and optokinetic (OKR) reflexes. While the organization of neuronal circuits underlying VOR is well described across vertebrates, less is known about the contribution and evolutionary origin of the OKR circuits. Moreover, the integration of these two sensory modalities is still poorly understood. Here, we developed a novel experimental model, the isolated lamprey eye-brain-labyrinth preparation, to analyze the neuronal pathways underlying visuo-vestibular integration which allowed electrophysiological recordings while applying vestibular stimulation using a moving platform, coordinated with visual stimulation via two screens. We show that lampreys exhibit robust visuo-vestibular integration, with optokinetic information processed in the pretectum 1 bioRxiv preprint doi: https://doi.org/10.1101/2021.07.30.454479; this version posted August 1, 2021.
  • Eye Fields in the Frontal Lobes of Primates

    Eye Fields in the Frontal Lobes of Primates

    Brain Research Reviews 32Ž. 2000 413±448 www.elsevier.comrlocaterbres Full-length review Eye fields in the frontal lobes of primates Edward J. Tehovnik ), Marc A. Sommer, I-Han Chou, Warren M. Slocum, Peter H. Schiller Department of Brain and CognitiÕe Sciences, Massachusetts Institute of Technology, E25-634, Cambridge, MA 02139, USA Accepted 19 October 1999 Abstract Two eye fields have been identified in the frontal lobes of primates: one is situated dorsomedially within the frontal cortex and will be referred to as the eye field within the dorsomedial frontal cortexŽ. DMFC ; the other resides dorsolaterally within the frontal cortex and is commonly referred to as the frontal eye fieldŽ. FEF . This review documents the similarities and differences between these eye fields. Although the DMFC and FEF are both active during the execution of saccadic and smooth pursuit eye movements, the FEF is more dedicated to these functions. Lesions of DMFC minimally affect the production of most types of saccadic eye movements and have no effect on the execution of smooth pursuit eye movements. In contrast, lesions of the FEF produce deficits in generating saccades to briefly presented targets, in the production of saccades to two or more sequentially presented targets, in the selection of simultaneously presented targets, and in the execution of smooth pursuit eye movements. For the most part, these deficits are prevalent in both monkeys and humans. Single-unit recording experiments have shown that the DMFC contains neurons that mediate both limb and eye movements, whereas the FEF seems to be involved in the execution of eye movements only.
  • Visual Pathways

    Visual Pathways

    Visual Pathways Michael Davidson Professor, Ophthalmology Diplomate, American College of Veterinary Ophthalmologists Department of Clinical Sciences College of Veterinary Medicine North Carolina State University Raleigh, North Carolina, USA <[email protected]> Vision in Animals Miller PE, Murphy CJ. Vision in Dogs. JAVMA. 1995; 207: 1623. Miller PE, Murphy CJ. Equine Vision. In Equine Ophthalmology ed. Gilger BC. 2nd ed. 2011: pp 398- 433. Ofri R. Optics and Physiology of Vision. In Veterinary Ophthalmology. ed. Gelatt KN 5th ed. 2013: 208-270, Visual Pathways, Responses and Reflexes: Relevant Structures Optic n (CN II) – somatic afferent Oculomotor n (CN III), Trochlear n (CN IV), Abducens n (CN VI) – somatic efferent to extraocular muscles Facial n (CN VII)– visceral efferent to eyelids Rostral colliculi – brainstem center that mediates somatic reflexes in response to visual stimuli Cerebellum Cerebro-cortex esp. occipital lobe www.studyblue.com Visual Pathway Visual Cortex Optic Radiation Lateral Geniculate Body www.studyblue.com Visual Field each cerebral hemisphere receives information from contralateral visual field (“the area that can be seen when the eye is directed forward”) visual field Visual Fiber (Retinotopic) Segregation nasal retinal fibers decussate at chiasm, temporal retinal fibers remain ipsilateral Nasal Temporal Retina Retina Fibers Fibers Decussate Remain Ipsilateral OD Visual Field OS Total visual field OD temporal nasal hemifield hemifield temporal nasal fibers fibers Nasal Temporal Retina = Retina = Temporal
  • Asymmetries of Dark and Bright Negative Afterimages Are Paralleled by Subcortical on and OFF Poststimulus Responses

    Asymmetries of Dark and Bright Negative Afterimages Are Paralleled by Subcortical on and OFF Poststimulus Responses

    1984 • The Journal of Neuroscience, February 22, 2017 • 37(8):1984–1996 Systems/Circuits Asymmetries of Dark and Bright Negative Afterimages Are Paralleled by Subcortical ON and OFF Poststimulus Responses X Hui Li,1,2 X Xu Liu,1,2 X Ian M. Andolina,1 Xiaohong Li,1 Yiliang Lu,1 Lothar Spillmann,3 and Wei Wang1 1Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China, 2University of Chinese Academy of Sciences, Shanghai 200031, China, and 3Department of Neurology, University of Freiburg, 79085 Freiburg, Germany Humans are more sensitive to luminance decrements than increments, as evidenced by lower thresholds and shorter latencies for dark stimuli. This asymmetry is consistent with results of neurophysiological recordings in dorsal lateral geniculate nucleus (dLGN) and primary visual cortex (V1) of cat and monkey. Specifically, V1 population responses demonstrate that darks elicit higher levels of activation than brights, and the latency of OFF responses in dLGN and V1 is shorter than that of ON responses. The removal of a dark or bright disc often generates the perception of a negative afterimage, and here we ask whether there also exist asymmetries for negative afterimages elicited by dark and bright discs. If so, do the poststimulus responses of subcortical ON and OFF cells parallel such afterimage asymmetries? To test these hypotheses, we performed psychophysical experiments in humans and single-cell/S-potential recordings in cat dLGN. Psychophysically, we found that bright afterimages elicited by luminance decrements are stronger and last longer than dark afterimages elicited by luminance increments of equal sizes.