B7.035 Visual System II

Question 1

how to test the medial rectus independently (without testing MLF)

Answer 1

looking at nose

independent of conjugate gaze pathway

Question 2

two bundles LGN fibers

Answer 2

travel to banks of the calcarine sulcus

1. parietal lobe fibers represent inferior visual field
2. temporal lobe fibers (Meyer’s loop) represent the superior visual field

Question 3

posterior occipital cortex

Answer 3

largest portion represents central vision (fovea)

Question 4

hemianopsia

Answer 4

1/2 of visual field is blacked out

Question 5

2 types of hemianopsia

Answer 5

1. bitemporal

2. homonymous

Question 6

what leads to macular sparing

Answer 6

collateral blood flow of macula

• PCA (most of visual cortex)
• MCA (most posterior region of visual cortex)

Question 7

how is input from the two eyes processed in the cortex?

Answer 7

incoming info from LGN is segregated into ocular dominance columns in the cortex
all cells in a column come from the same eye
columns alternate back and forth in a normal person

Question 8

how are ocular dominance columns formed

Answer 8

not hard wired
can change amount of cortical space that represents a particular function based on usage
malleable during specific periods of development

Question 9

where is input from two eyes finally merged?

Answer 9

cells enter in 4th layer

input merged in more superficial and deep cortical layers

Question 10

strabismus

Answer 10

“lazy eye”

Question 11

result of strabismus

Answer 11

can interfere with establishing binocular neuronal processing in the cortex
no merging of the two inputs ever occurs, columns stay separate at all layers

Question 12

what happens between birth and adulthood in the visual cortex

Answer 12

initially eye input is more intertwined

by adulthood, separate into columns in the 4th layer, and mixing only occurs below and above