Visual Anatomy-Lect2 Flashcards
Where does the light go when it enters the eye describe process
The photoreceptors (rods and cones) in the retina (at back of eye) transduce the light into neural signals
What is the Blind spot
The point at which the optic nerve leaves the eye, no rods and cones present there.
Name the main pathway for info to go from retina to the brain/ to V1?
There are abt 10 but the main one travels to the primary visual cortex (V1) via the LATERAL GENICULATE NUCLEUS (LGN) located in Thalamus. One LGN in each hemisphere. The V1 comprises a route called the GENICULO-STRIATE PATHWAY.
In LGN, how is the info received divided/sub divided?
LGN has 6 layers ; top 4 layers called PARVOCELLULAR due to having small cell bodies, used for colour and fine details ; lower 2 layers are called MAGNOCELLULARS,has larger cell bodies, used for depth and movement
Name for the occipital cortex outside V1 and name the areas specialised for other visual functions
It is called Extrastriate cortex and includes V4 and V5 (or MT). V4 = for colour ; V5 = for movement
So when looking at smthg, different aspects are processed by different brain regions = specialisation
damage to V4 and damage to V5 can lead to …
V4 Damage = Achromatopsia, colour blindness
V5 damage = Akinetopsia
Who proposed the two visual systems hypothesis?
Milner & Goodale 1995 proposed 2 main routes outside of V1 : The VENTRAL (what) route for details and identity, and the DORSAL (where) route for motion, location
= So conscious visual perceptions and visuomotor control would be separate functions
Name and describe two patients supporting the 2 visual hypothesis
Patient DF had a damage to the ventral route, she could not recognise familiar objects and faces (visual agnosia), could not judge size or orientation but had no issue doing these in action.
Patient RV had damage to the dorsal route and showed opposite pattern. Difficulty grasping and pointing towards visual objects but no problem to identify them (optic ataxia).
What do patients DF and RV show?
Double dissociation between visual perception and visuomotor performance, show that both functions can be selectively and independently impaired, thus supporting the 2 visual systems account.
