Lecture 13 Flashcards
What is blindsight and how does it work?
Blindsight is when you can localise where objects are but can’t see them. The shape can be typically sensed (though not sure what is sensed) when moved. This can occur through secondary pathways in the eye, these allow it to skip LGN and V1 and meet up later (e.g V5, this is on the dorsal pathway to the Parietal lobe, which is to do with where something is). When jiggled the V5 area (responsible for motion vision), start acting, hence the blindsight patient can sense the object, but not tell what it is(as visual cortex is skipped due to LGN and V1 skipping.
What are 6 examples of visual problems?
achromatopsia (absence of colour vision due to damage to V4), Akinetopsia(absence of motion vision, damage to V5). Visual agnosia involves several different types, appercetive agnosia is failure of object recognition due to failure of visual perception, preserved elementary visual function(can see colour, movement, can see that something is there, but struggle to tell what it is) and poor matching and copying, this mostly occurs due to problems with V1, the occipital lobe and possibly some parietal. Dorsal Simultagnosia is failure of object recognition due to a spatial perceptual impairment, preserved elementary visual function, able to recognize objects but only one at a time, this is due to damage to the parietal lobe, it is hard for them to understand what is going on with the objects because it is like trying to make a story from a series of objects, with no idea where they are in relation. Ventral simultagnosia is failure of object recognition due to a complex perceptual problem, can recognize objects, only one at a time, but can see multiple objects at the same time. Associative agnosia is failure of object recognition due to a higher order complex perceptual impairment, copying is accurate, but slavish (difficult).
What is the peppery mask hypothesis?
The peppery mask hypothesis says that if we damage one cell in the V1 area it will lead to a black spot in our vision, this means if large amounts are damaged all over the place it will be like viewing the world through a peppery mask, this is a possibility for how Appercetive agnosia is caused. This means movement helps vision as it moves the black spot locations relative to the object.
