DOCSLIB.ORG

Motion Detection in Blindsight

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Motion Detection in Blindsight City Research Online City, University of London Institutional Repository Citation: Moro, Sancho (2004). A study of pupil response components in human vision. (Unpublished Doctoral thesis, City University London) This is the unspecified version of the paper. This version of the publication may differ from the final published version. Permanent repository link: https://openaccess.city.ac.uk/id/eprint/3084/ Link to published version: Copyright: City Research Online aims to make research outputs of City, University of London available to a wider audience. Copyright and Moral Rights remain with the author(s) and/or copyright holders. URLs from City Research Online may be freely distributed and linked to. Reuse: Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. City Research Online: http://openaccess.city.ac.uk/ [email protected] A study of pupil response components in human vision Sancho Moro Dissertation submitted for a Philosophical Doctorate degree at City University, London Department of Optometry and Visual Science July 2004 Table of Contents Acknowledgements ....................................................................................................................... 10 Abstract ......................................................................................................................................... 12 Thesis outline and summary of research .................................................................................... 13 Chapter 1: Anatomy and Physiology of the Visual System .......................................................15 1.1 Photo-transduction in the retina ........................................................................................15 1.2 The retina..........................................................................................................................16 1.3 Horizontal, amacrine and bipolar retinal cells ..................................................................18 1.4 Retino-geniculate pathway................................................................................................19 1.5 Retinal ganglion cells........................................................................................................20 1.6 The lateral geniculate nucleus (LGN) of the thalamus......................................................25 1.7 Functional organisation of the brain .................................................................................29 1.8 Visual striate cortex (V1)..................................................................................................29 1.9 Extra-striate areas V2, V3, V4 and V5 .............................................................................35 1.10 Non geniculo-striate pathways.....................................................................................37 1.11 Models for visual perception........................................................................................40 Chapter 2: The Role of the Pupil in Human Vision ...................................................................43 2.1 The iris and the pupil ........................................................................................................43 2.2 Effects on retinal image quality ........................................................................................43 2.3 Factors affecting pupil size ...............................................................................................43 2.4 Innervation of the iris sphincter and dilator muscles ........................................................46 2.5 The neural pathways of the pupil light reflex (PLR) ........................................................46 2.6 Sympathetic and parasympathetic neuro-transmitters.......................................................51 2.7 Asymmetry in constriction and dilation rates ...................................................................51 2.8 Drugs affecting pupil size .................................................................................................52 2.9 Disorders of the pupil........................................................................................................53 2.10 Summary ......................................................................................................................55 Chapter 3: Methods ......................................................................................................................57 3.1 Introduction.......................................................................................................................57 3.2 Basic Photometry and Colorimetry...................................................................................57 3.3 Computer displays: luminance and colour calibration......................................................61 3.4 Experimental set-up during psychophysics and pupillometry ..........................................63 3.5 Pupil measurements: the P_SCAN system .......................................................................64 3.6 Periodic modulation and Fourier signal analysis ..............................................................66 3.7 Use of isoluminant stimuli................................................................................................69 3.8 Doubly isoluminant coloured stimuli................................................................................69 3.9 Visual psychophysics........................................................................................................70 Chapter 4: Pupil responses to different visual stimulus attributes...........................................72 4.1 Pupil Light Reflex (PLR) response measurements ...........................................................72 4.2 Pupil responses to isoluminant stimuli..............................................................................75 4.3 Pupil Colour Response (PCR) measurements...................................................................76 4.4 Pupil Grating Response (PGR) measurements..................................................................77 4.5 Pupil Perimetry .................................................................................................................79 4.6 Spatial summation in the PLR ..........................................................................................82 2 4.7 Discussion.........................................................................................................................85 4.8 Summary...........................................................................................................................89 Chapter 5: Effect of cortical lesions on the pupil response........................................................91 1.1 Introduction: 'blindsight' ...................................................................................................91 5.1 Patients’ medical histories ................................................................................................92 5.2 Methods ............................................................................................................................92 5.3 Experiments and results ....................................................................................................93 5.4 Summary and discussion...................................................................................................98 Chapter 6: Effect of pretectal lesions on the pupil response .....................................................99 6.1 Introduction: Parinaud's syndrome ...................................................................................99 6.2 Patients’ medical histories ................................................................................................99 6.3 Methods ..........................................................................................................................100 6.4 Experiments and results ..................................................................................................102 6.5 Summary.........................................................................................................................107 6.6 Discussion.......................................................................................................................107 Chapter 7: Clinical applications of the pupil response ............................................................109 7.1 Optic neuritis (ON) and Multiple Sclerosis (MS) ...........................................................109 7.2 Methods and subject groups............................................................................................110 7.3 Data analysis and results: Group 1..................................................................................115 7.4 Data analysis and results: Group 2..................................................................................117 7.5 Discussion.......................................................................................................................123 Directions for further research ................................................................................................ 126 References .................................................................................................................................
Load more

Recommended publications
  • Vision Research Xxx (2015) Xxx–Xxx
    Vision Research xxx (2015) xxx–xxx Contents lists available at ScienceDirect Vision Research journal homepage: www.elsevier.com/locate/visres Altered white matter in early visual pathways of humans with amblyopia ⇑ Brian Allen a, Daniel P. Spiegel c,d, Benjamin Thompson c,e, Franco Pestilli b,1, Bas Rokers a, ,1 a Department of Psychology, University of Wisconsin-Madison, Madison, WI, United States b Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, United States c Optometry and Vision Science, University of Auckland, Auckland, New Zealand d McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Canada e Optometry and Vision Science, University of Waterloo, Canada article info abstract Article history: Amblyopia is a visual disorder caused by poorly coordinated binocular input during development. Little is Received 8 September 2014 known about the impact of amblyopia on the white matter within the visual system. We studied the Received in revised form 16 December 2014 properties of six major visual white-matter pathways in a group of adults with amblyopia (n = 10) and Available online xxxx matched controls (n = 10) using diffusion weighted imaging (DWI) and fiber tractography. While we did not find significant differences in diffusion properties in cortico-cortical pathways, patients with Keywords: amblyopia exhibited increased mean diffusivity in thalamo-cortical visual pathways. These findings sug- Amblyopia gest that amblyopia may systematically alter the white matter properties of early visual pathways. White matter 2015 Elsevier Ltd. All rights reserved. Tractography Ó Diffusion-MRI 1. Introduction absent sensitivity to binocular disparity (Holmes & Clarke, 2006; Li et al., 2011). Amblyopia is a developmental disorder that occurs when the The neuro-anatomical consequences of amblyopia in humans visual input from the two eyes is poorly correlated during early are less established than the functional deficits.
    [Show full text]
  • The Nature of Foveal Representation Projections from the Nasal Part of the Retinae to Reach the Ipsilateral Hemispheres
    PERSPECTIVES OPINION hemiretina, project to the ‘wrong’ laminae of the LGN. These results were taken to show that the crossing of the nasal retinal fibres in the optic chiasm is incomplete, allowing some The nature of foveal representation projections from the nasal part of the retinae to reach the ipsilateral hemispheres. Normally, Michal Lavidor and Vincent Walsh however, foveal stimuli received by the nasal retinae are projected to the contralateral visual Abstract | A fundamental question in visual the visual midline. This is what Descartes1 cortex. A later study10 indicated that the perception is whether the representation of suggested in his description of the visual dendritic coverage of the centre of the fovea the fovea is split at the midline between the system — he identified the pineal gland as the by RGCs provides a possible neural basis for two hemispheres, or bilaterally represented organ of integration (FIG. 1).Unfortunately, 2–3° of bilateral representation of the fovea by overlapping projections of the fovea in this intuitive, appealing explanation is in the central visual pathways. There is also each hemisphere. Here we examine not true, and we therefore have to assume evidence that the nasotemporal overlap psychophysical, anatomical, that the two cerebral hemispheres cooperate increases towards the upper and lower regions neuropsychological and brain stimulation or compete over the representation of the of the retina11. experiments that have addressed this human foveal area. Most studies that have labelled RGCs with question, and argue for a shift from the When a person is fixating centrally (looking HRP after unilateral injections into the mon- current default view of bilateral straight ahead), information that is to key optic tract have found a nasotemporal representation to that of a split the right of fixation (in the right visual field) is overlap zone along the vertical meridian12.
    [Show full text]
  • (Homonymous Hemianopsia): Tapping Into Blindsight
    CORE Metadata, citation and similar papers at core.ac.uk Provided by Elsevier - Publisher Connector Journal of Medical Hypotheses and Ideas (2015) 9,S8–S13 Available online at www.sciencedirect.com Journal of Medical Hypotheses and Ideas journal homepage: www.elsevier.com/locate/jmhi REGULAR ARTICLE Enhancing visual performance in individuals with cortical visual impairment (homonymous hemianopsia): Tapping into blindsight Faith A. Birnbaum a, Steven A. Hackley b, Lenworth N. Johnson a,* a Neuro-Ophthalmology Unit, Department of Ophthalmology, The Warren Alpert Medical School of Brown University/Lifespan/Rhode Island Hospital, Providence, RI, United States b Department of Psychological Sciences of the University of Missouri Columbia, Columbia, MO, United States Received 2 October 2015; revised 29 November 2015; accepted 15 December 2015 Available online 22 January 2016 KEYWORDS Abstract Homonymous hemianopsia is a type of cortical blindness in which vision is lost Blindsight; completely or partially in the left half or the right half of the field of vision. It is prevalent in Cortical blindness; approximately 12% of traumatic brain injury and 35% of strokes. Patients often experience Homonymous hemianopsia; difficulty with activities such as ambulating, eating, reading, and driving. Due to the high prevalence Augmented virtual reality; of homonymous hemianopsia and its associated difficulties, it is imperative to find methods for Vision restoration therapy visual rehabilitation in this condition. Traditional methods such as prism glasses can cause visual confusion and result in patient noncompliance. There is a large unmet medical need for improving this condition. In this article, we propose that modifying visual stimuli to activate non-cortical areas of visual processing, such as lateral geniculate nucleus and superior colliculus, may result in increased visual awareness.
    [Show full text]
  • Affections of Uvea Affections of Uvea
    AFFECTIONS OF UVEA AFFECTIONS OF UVEA Anatomy and physiology: • Uvea is the vascular coat of the eye lying beneath the sclera. • It consists of the uvea and uveal tract. • It consists of 3 parts: Iris, the anterior portion; Ciliary body, the middle part; Choroid, the third and the posterior most part. • All the parts of uvea are intimately associated. Iris • It is spongy having the connective tissue stroma, muscular fibers and abundance of vessels and nerves. • It is lined anteriorly by endothelium and posteriorly by a pigmented epithelium. • Its color is because of amount of melanin pigment. Mostly it is brown or golden yellow. • Iris has two muscles; the sphincter which encircles the pupil and has parasympathetic innervation; the dilator which extends from near the sphincter and has sympathetic innervation. • Iris regulates the amount of light admitted to the interior through pupil. • The iris separates the anterior chamber from the posterior chamber of the eye. Ciliary Body: • It extends backward from the base of the iris to the anterior part of the choroid. • It has ciliary muscle and the ciliary processes (70 to 80 in number) which are covered by ciliary epithelium. Choroid: • It is located between the sclera and the retina. • It extends from the ciliaris retinae to the opening of the optic nerve. • It is composed mainly of blood vessels and the pigmented tissue., The pupil • It is circular and regular opening formed by the iris and is larger in dogs in comparison to man. • It contracts or dilates depending upon the light source, due the sphincter and dilator muscles of the iris, respectively.
    [Show full text]
  • Foveola Nonpeeling Internal Limiting Membrane Surgery to Prevent Inner Retinal Damages in Early Stage 2 Idiopathic Macula Hole
    Graefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-014-2613-7 RETINAL DISORDERS Foveola nonpeeling internal limiting membrane surgery to prevent inner retinal damages in early stage 2 idiopathic macula hole Tzyy-Chang Ho & Chung-May Yang & Jen-Shang Huang & Chang-Hao Yang & Muh-Shy Chen Received: 29 October 2013 /Revised: 26 February 2014 /Accepted: 5 March 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Keywords Fovea . Foveola . Internal limiting membrane . Purpose The purpose of this study was to investigate and macular hole . Müller cell . Vitrectomy present the results of a new vitrectomy technique to preserve the foveolar internal limiting membrane (ILM) during ILM peeling in early stage 2 macular holes (MH). Introduction Methods The medical records of 28 consecutive patients (28 eyes) with early stage 2 MH were retrospectively reviewed It is generally agreed that internal limiting membrane (ILM) and randomly divided into two groups by the extent of ILM peeling is important in achieving closure of macular holes peeing. Group 1: foveolar ILM nonpeeling group (14 eyes), (MH) [1]. An autopsy study of a patient who had undergone and group 2: total peeling of foveal ILM group (14 eyes). A successful MH closure showed an area of absent ILM sur- donut-shaped ILM was peeled off, leaving a 400-μm-diameter rounding the sealed MH [2]. ILM over foveola in group 1. The present ILM peeling surgery of idiopathic MH in- Results Smooth and symmetric umbo foveolar contour was cludes total removal of foveolar ILM. However, removal of restored without inner retinal dimpling in all eyes in group 1, all the ILM over the foveola causes anatomical changes of the but not in group 2.
    [Show full text]
  • Abnormal Retinotopic Representations in Human Visual Cortex Revealed by Fmri
    Acta Psychologica 107 -2001) 229±247 www.elsevier.com/locate/actpsy Abnormal retinotopic representations in human visual cortex revealed by fMRI Antony B. Morland a,*, Heidi A. Baseler c, Michael B. Homann a, Lindsay T. Sharpe b, Brian A. Wandell c a Psychology Department, University of London, Royal Holloway, Egham, Surrey TW20 0EX, UK b Psychology Department, Newcastle University, Newcastle, UK c Psychology Department, Stanford University, CA 93155, USA Received 1 September 2000; received in revised form 8 December 2000; accepted 11 December 2000 Abstract The representation of the visual ®eld in early visual areas is retinotopic. The point-to-point relationship on the retina is therefore maintained on the convoluted cortical surface. Func- tional magnetic resonance imaging -fMRI) has been able to demonstrate the retinotopic representation of the visual ®eld in occipital cortex of normal subjects. Furthermore, visual areas that are retinotopic can be identi®ed on computationally ¯attened cortical maps on the basis of positions of the vertical and horizontal meridians. Here, we investigate abnormal retinotopic representations in human visual cortex with fMRI. We present three case studies in which patients with visual disorders are investigated. We have tested a subject who only possesses operating rod photoreceptors. We ®nd in this case that the cortex undergoes a re- mapping whereby regions that would normally represent central ®eld locations now map more peripheral positions in the visual ®eld. In a human albino we also ®nd abnormal visual cortical activity. Monocular stimulation of each hemi®eld resulted in activations in the hemisphere contralateral to the stimulated eye. This is consistent with abnormal decussation at the optic chiasm in albinism.
    [Show full text]
  • Clinical Study of Etiopathogenesis of Isolated Oculomotor Nerve Palsy
    CLINICAL STUDY OF ETIOPATHOGENESIS OF ISOLATED OCULOMOTOR NERVE PALSY DISSERTATION SUBMITTED TO In partial fulfillment of the requirement for the degree of M.S. DEGREE EXAMINATION OF BRANCH III OPHTHALMOLOGY of THE TAMIL NADU DR. M. G. R MEDICAL UNIVERSITY CHENNAI- 600032 DEPARTMENT OF OPHTHALMOLOGY TIRUNELVELI MEDICAL COLLEGE TIRUNELVELI- 11 APRIL 2015 CERTIFICATE This is to certify that this dissertation entitled “Clinical Study Of Etiopathogenesis Of Isolated Oculomotor Nerve Palsy” submitted by Dr. Saranya.K.V to the faculty of Ophthalmology ,The Tamil Nadu Dr. MGR Medical University, Chennai in partial fulfillment of the requirement for the award of M.S Degree Branch III (Ophthalmology), is a bonafide research work carried out by her under my direct supervision and guidance. Dr. L.D.THULASI RAM MS. (Ortho) Dr A.YOGESWARI. The Dean Professor & Head of the Department Tirunelveli Medical College, Department of Ophthalmology Tirunelveli Tirunelveli Medical College, Tirunelveli. DECLARATION BY THE CANDIDATE I hereby declare that this dissertation entitled “Clinical Study Of Etiopathogenesis Of Isolated Oculomotor Nerve Palsy” is a bonafide and genuine research work carried out by me under the guidance of Dr. RITA HEPSI RANI .M, Assistant Professor of Ophthalmology, Department of Ophthalmology, Tirunelveli Medical College, Tirunelveli Dr. Saranya.K.V Post Graduate In Ophthalmology, Department Of Ophthalmology, Tirunelveli Medical College, Tirunelveli. ACKNOWLEDGEMENT I express my sincere gratitude and thanks to The Dean, Tirunelveli Medical College, Tirunelveli, for providing all the facilities to conduct this study. I sincerely thank Dr.A.Yogeswari Professor and HOD, Dept of Ophthalmology for her valuable advice, comments and constant encouragement for the completion of this study.
    [Show full text]
  • Retinal Anatomy and Histology
    1 Q Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? 2 Q/A Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? While often used interchangeably (including, on occasion, in this slide-set), these are technically not synonyms. The term neurosensory retina refers to the neural lining on the inside of the eye, whereas the term retina refers to this neural lining along with the retinal pigmentthree epithelium words (RPE). 3 A Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? While often used interchangeably (including, on occasion, in this slide-set), these are technically not synonyms. The term neurosensory retina refers to the neural lining on the inside of the eye, whereas the term retina refers to this neural lining along with the retinal pigment epithelium (RPE). 4 Q Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? While often used interchangeably (including, on occasion, in this slide-set), these are technically not synonyms. The term neurosensory retina refers to the neural lining on the inside of the eye, whereas the term retina refers to this neural lining along with the retinal pigment epithelium (RPE). The neurosensory retina contains three classes of cells—what are they? There are five types of neural elements—what are they? What are the three types of glial cells? The two vascular cell types? --? ----PRs ----Bipolar cells ----Ganglion cells ----Amacrine cells ----Horizontal cells --? ----Müeller cells ----Astrocytes ----Microglia --? ----Endothelial cells ----Pericytes 5 A Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? While often used interchangeably (including, on occasion, in this slide-set), these are technically not synonyms.
    [Show full text]
  • Anatomy and Physiology of the Afferent Visual System
    Handbook of Clinical Neurology, Vol. 102 (3rd series) Neuro-ophthalmology C. Kennard and R.J. Leigh, Editors # 2011 Elsevier B.V. All rights reserved Chapter 1 Anatomy and physiology of the afferent visual system SASHANK PRASAD 1* AND STEVEN L. GALETTA 2 1Division of Neuro-ophthalmology, Department of Neurology, Brigham and Womens Hospital, Harvard Medical School, Boston, MA, USA 2Neuro-ophthalmology Division, Department of Neurology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA INTRODUCTION light without distortion (Maurice, 1970). The tear–air interface and cornea contribute more to the focusing Visual processing poses an enormous computational of light than the lens does; unlike the lens, however, the challenge for the brain, which has evolved highly focusing power of the cornea is fixed. The ciliary mus- organized and efficient neural systems to meet these cles dynamically adjust the shape of the lens in order demands. In primates, approximately 55% of the cortex to focus light optimally from varying distances upon is specialized for visual processing (compared to 3% for the retina (accommodation). The total amount of light auditory processing and 11% for somatosensory pro- reaching the retina is controlled by regulation of the cessing) (Felleman and Van Essen, 1991). Over the past pupil aperture. Ultimately, the visual image becomes several decades there has been an explosion in scientific projected upside-down and backwards on to the retina understanding of these complex pathways and net- (Fishman, 1973). works. Detailed knowledge of the anatomy of the visual The majority of the blood supply to structures of the system, in combination with skilled examination, allows eye arrives via the ophthalmic artery, which is the first precise localization of neuropathological processes.
    [Show full text]
  • Neuropsychologia 128 (2019) 150–165
    Neuropsychologia 128 (2019) 150–165 Contents lists available at ScienceDirect Neuropsychologia journal homepage: www.elsevier.com/locate/neuropsychologia Psychophysical and neuroimaging responses to moving stimuli in a patient with the Riddoch phenomenon due to bilateral visual cortex lesions T Michael J. Arcaroa,b,c, Lore Thalerd, Derek J. Quinlane, Simona Monacof, Sarah Khang, Kenneth F. Valyearh, Rainer Goebeli, Gordon N. Duttonj, Melvyn A. Goodalee,g, Sabine Kastnerb,c, ⁎ Jody C. Culhame,g, a Department of Neurobiology, Harvard Medical School, Boston, MA, USA b Department of Psychology, Princeton University, Princeton, NJ, USA c Princeton Neuroscience Institute, Princeton, NJ, USA d Department of Psychology, Durham University, Durham, UK e Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada f Center for Mind and Brain Sciences, University of Trento, Trento, Italy g Department of Psychology, University of Western Ontario, London, Ontario, Canada h School of Psychology, University of Bangor, Bangor, Wales i Department of Cognitive Neuroscience, Maastricht University, Maastricht, The Netherlands j Department of Visual Science, Glasgow Caledonian University, Glasgow, UK ARTICLE INFO ABSTRACT Keywords: Patients with injury to early visual cortex or its inputs can display the Riddoch phenomenon: preserved Riddoch phenomenon awareness for moving but not stationary stimuli. We provide a detailed case report of a patient with the Riddoch Blindsight phenomenon, MC. MC has extensive bilateral lesions to occipitotemporal cortex that include most early visual Vision cortex and complete blindness in visual field perimetry testing with static targets. Nevertheless, she shows a Motion perception remarkably robust preserved ability to perceive motion, enabling her to navigate through cluttered environ- FMRI ments and perform actions like catching moving balls.
    [Show full text]
  • Pupils and Near Vision
    PUPILS AND NEAR VISION Akilesh Gokul PhD Research Fellow Department of Ophthalmology Iris Anatomy Two muscles: • Radially oriented dilator (actually a myo-epithelium) - like the spokes of a wagon wheel • Sphincter/constrictor Pupillary Reflex • Size of pupil determined by balance between parasympathetic and sympathetic input • Parasympathetic constricts the pupil via sphincter muscle • Sympathetic dilates the pupil via dilator muscle • Response to light mediated by parasympathetic; • Increased innervation = pupil constriction • Decreased innervation = pupil dilation Parasympathetic Pathway 1. Three major divisions of neurons: • Afferent division 2. • Interneuron division • Efferent division Near response: • Convergence 3. • Accommodation • Pupillary constriction Pupil Light Parasympathetic – Afferent Pathway 1. • Retinal ganglion cells travel via the optic nerve leaving the optic tracts 2. before the LGB, and synapse in the pre-tectal nucleus. 3. Pupil Light Parasympathetic – Efferent Pathway 1. • Pre-tectal nucleus nerve fibres partially decussate to innervate both Edinger- 2. Westphal (EW) nuclei. • E-W nucleus to ipsilateral ciliary ganglion. Fibres travel via inferior division of III cranial nerve to ciliary ganglion via nerve to inferior oblique muscle. 3. • Ciliary ganglion via short ciliary nerves to innervate sphincter pupillae muscle. Near response: 1. Increased accommodation Pupil 2. Convergence 3. Pupillary constriction Sympathetic pathway • From hypothalamus uncrossed fibres 1. down brainstem to terminate in ciliospinal centre
    [Show full text]
  • Visual Problems After Brain Injury
    Visual problems after brain injury As a charity, we rely on donations from people like you to continue providing free information to people affected by brain injury. Donate today: www.headway.org.uk/donate Introduction Vision is the skill that allows us to see the world around us. When we look at the world, a complex series of processes takes place between the eyes and the brain. The eyes take in the information, while the brain (which is connected to the eyes by a nerve called the optic nerve) is responsible for processing and interpreting it. Through this system we are able to see things such as colours, shapes, movement, objects and people. When the brain is injured, the ability to interpret visual information can be affected in different ways. This factsheet has been written to explain how brain injury can affect vision and how to seek professional support with these issues. Tips for coping with visual problems are also offered. Words in bold are defined in a glossary at the end of the factsheet. What is vision? There are lots of different aspects of vision. Some of the things the brain needs to do to decode information that it receives from the eyes are: • process the shape and colour of objects • process and merge information received from both eyes • recall information from memory to recognise objects or places • process the movement of objects • process the location and position of an object in space • process information across the visual field (including peripheral vision) Generally, different parts of the brain are responsible for processing these different aspects of vision.
    [Show full text]