Lecture 10 - Visual thalamus and cortex

Left visual hemifield represented in

both retinas, both optic nerves, right optic tract, right lateral geniculate nucleus, right primary visual cortex

LGN layers represent

entire map of contralateral visual hemifield, layers 146 is contralateral side, layers 235 is ipsilateral side

LGN cells RF

ON center and OFF center

Ocular dominance columns

zebra stripe patterns, patches in layer 4C in primary visual cortex that receive input from one eye

Where is information from both eyes first combined

layer 3 of primary visual cortex

V1 cells respond best to

oriented lines and some are direction selective so they respond to an oriented line moving in one direction but not the opposite

As you move perpendicular to the surface of V1, orientational selectivity of cells (stays the same/changes)

stays the same

As you move parallel to the surface of V1, orientational selectivity of cells (stays the same/changes)

changes

Simple cell and RF

in V1 that has distinct ON and OFF regions from converging LGN input, orientation

Complex cell and RF

in V1 that has no distinct ON and OFF regions from converging simple cell input. Responds to stimulus at preferred orientation anywhere in the RF

Blobs

In V1 layers 2356, look like spots, high levels of cytochrome oxidase, contribute to color processing

Visual “what” pathway in cortex

V1 - V2 - V4 - IT - anterior temporal areas

Visual “how/where” pathway in cortex

V1 - V2 - V3 - MT - MST - parietal areas

V2 cells respond best to

angles and combinations of lines from converging V1 cell input

V4 cells respond best to

form and color (colored shapes) from converging V2 cell input

MT cells respond best to

middle temporal cells respond to stimuli moving in particular directions