Visual Cortex

Question 1

Columnal Organization

layer 4?

Answer 1

– Like all of Cerebral Cortex, Visual Cortex has six layers of cells;
- Layer 4 receives input from LGN

Question 2

All cells within a given Column of perceptual cortex show:

e.g.?

Answer 2

same “preferred stimulus” (i.e. react best to same stimulus)

• e.g. Cells each column respond to lines oriented in one particular Orientation (e.g. ||||| vs. ///// vs. = vs. \\\ etc)

Question 3

All cells within a Hypercolumn (set of columns)

Answer 3

• have same Receptive Field
• One Hypercolumn includes cols for 1 full set of Orientations, plus “Blobs” for color processing, from same area of retina

Question 4

Retinotopic Map

Answer 4

• reproduces retinal layout such that adjacent columns of Cortical cells have adjacent RFs in Retina

-This topological map preserves spatial relationships (area A next to B next to C etc. in both the Retina and the Cortex)
=> altho not necessarily absolute distances (e.g. distance from A to C in Retina may be greater/less than A to C in Cortex)

Question 5

Magnification Factor

Answer 5

Cortical cells with small RFs fill a disproportionally large area of the visual projection areas
- e.g. The Fovea takes up only .01% of the Retina, but 8% of V1

Question 6

Imagery (in absence of actual visual input)

Answer 6

activates many of the same areas of Visual Cortex as actual input

• e.g. Visualize distant mouse, macular (fovea and nearby) map active; Visualize close-up elephant, peripheral map also active