physiology of visual cortex objectives - michael

Question 1

2) Organization of the visual cortex

Answer 1

a) Primary visual cortex is located on the medial surface of the occipital lobe
b) Visual association cortex surrounds the primary visual cortex, including portions of temporal lobe
c) 6 layers of cells; input from lateral geniculate terminates in layer 4; information then flows to layers 2/3, then to layer 5, then to layer 6
d) Layers 2/3 project to other cortical regions; layer 6 projects back to the lateral geniculate
e) A disproportionate volume of visual cortex is dedicated to information from the fovea
f) There is a point-to-point projection from retina to lateral geniculate and from geniculate to visual cortex
i) From the retina to the primary visual cortex, the image is inverted (top-to-bottom and left-to-right)
ii) In the lateral geniculate, the nasal half of each retina decussates so that each side receives half of the input from each eye (see figure on right)
iii) Ephrin (Eph) signaling: Temporal retinal ganglion cells produce Ephrin B1 and cells at the optic chiasm produce Ephrin B2. B1 and B2 interate to produce a repulsive signal that prevents temporal retinal ganglion cells from crossing over
iv) The upper half of the visual field projects to Meyer’s loop (below the calcarine sulcus)

Question 2

a) Primary visual cortex

Answer 2

located on the medial surface of the occipital lobe

Question 3

b) Visual association cortex

Answer 3

surrounds the primary visual cortex, including portions of temporal lobe

Question 4

d) Layers 2/3 projects to

Answer 4

project to other cortical regions

Question 5

layer 6 projects to

Answer 5

back to the lateral geniculate

Question 6

flow of information through the visual cortex

Answer 6

input from lateral geniculate terminates in layer 4; information then flows to layers 2/3, then to layer 5, then to layer

Question 7

point-to-point projection

Answer 7

f) There is a point-to-point projection from retina to lateral geniculate and from geniculate to visual cortex
i) From the retina to the primary visual cortex, the image is inverted (top-to-bottom and left-to-right)
ii) In the lateral geniculate, the nasal half of each retina decussates so that each side receives half of the input from each eye (see figure on right)
iii) Ephrin (Eph) signaling: Temporal retinal ganglion cells produce Ephrin B1 and cells at the optic chiasm produce Ephrin B2. B1 and B2 interate to produce a repulsive signal that prevents temporal retinal ganglion cells from crossing over
iv) The upper half of the visual field projects to Meyer’s loop (below the calcarine sulcus)

Question 8

iii) Ephrin (Eph) signaling

Answer 8

Temporal retinal ganglion cells produce Ephrin B1 and cells at the optic chiasm produce Ephrin B2. B1 and B2 interate to produce a repulsive signal that prevents temporal retinal ganglion cells from crossing over

Question 9

Meyer’s loop

Answer 9

iv) The upper half of the visual field projects to this

below the calcarine sulcus