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lec 5 - retina.docx

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University of Toronto Scarborough
Ted Petit

Oct 17 Lec 5 Retina – part of CNS - All info starts here (comes in here first) - Eyes grows out of brain -> developmentally part of the brain - Divided down center of retina ( 2 portions ) o Nasal portion -> closest to nose o Temporal portion -> outside portion -> closest to side of head - Cortex –visual cortex – area 17 - Nerves connects through to: o Optic nerve  Nerve -> pathway  Realistically it is a part of the CNS but break rule and call it optic nerve o Optic chiasm  Cross over of some nerves between retina and cortex  Temporal portion comes in to chiasm and leaves same side it was from  Nasal portion nerves cross over then goes into the brain  From retina on right side, leaves chiasm on left side... vice versa  Object in right visual field, hits nasal(left) of right eye, temporal(left) of left eye  Object in left visual field, hits temporal(right) of right eye, nasal(right) of left eye  Assuming looking straight ahead with BOTH eyes– middle is center  Right visual field (right half)  Left visual field (left half)  “grandma can’t see something in right side of visual field”  Not just wrong with the right eye  Remember how both eyes are used to see a visual field o Optic tract  It’s called a tract even though being same as a nerve  Called a tract when nerve is inside brain - Further system is ->simpler the system o Response to a specific stimulus (on and off) – Light source hitting on spot on retina - Closer to main area -> neurons put info all together o Neurons at visual cortex -> works with lines and orientation o Associational cortex -> does more complex works and interprets what you see - ..... Directly related to where the damage is - Images on slide: NOT RETINA -> JUST MAPPED VISUAL FIELD o Blacked out area = can’t see that area (visual field)  I.e. Black area on left side of visual field of left eye = nasal(right side) of left eye can’t see o Maps one eye at a time o Inner circle shows actual visual field  Retina is not perfectly circular o ALWAYS KEEP IN MIND OF 2 PORTIONS OF RETINA Macular sparing - Not complete blindness, some middle area not blind – very small area at very center of visual field If complete damage in occipital cortex - i.e. Massive stroke in cerebral posterior artery o Gets complete blindness in opposite side If incomplete damage – small amount - Get partial blindness in opposite side - Scotoma -> small area of blindness caused by a small area of damage o Most of the time don’t notice because brain is “plastic” – brain makes up for it o Natural blind spot is like a scotoma -> recall intro psych textbook example 17 - Primary area in occipital cortex Associated areas: 18, 19, 21 Right side: more patterns, complex patterns Left side: association, language, name of objects and stuff Syndromes to describe human behaviours - Today described what people can’t see - i.e. Some1 sees Martians shooting them or stuff -> schizophrenia Visual agnosia (a syndrome) - Cannot recognize objects: what it is or its function - Can’t decipher very complex forms o i.e. faces but that’s another syndrome o mainly objects - usually caused by damage to left of occipital lobe Prosopagnosia - person cannot distinguish faces o know it’s a person and human being but don’t know face - faces are very complex o mouth, eyes, nose, dif color hair, skin tone o but overall, very similar  takes a lot of visual awareness to differentiate - bilateral damage to associational cortex 18 and 19 -> varies - cannot recognize other complex
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