KD - Vision III

Question 1

Where do ganglion cells in the optic tract project to (4)

Answer 1

• Pretectum: feeds back to constrictor muscle in iris => pupillary light reflex
• Suprachiasmatic nucleus (hypothalamus): circadian (day – night) cycle
• Superior colliculus: coordination of movement in response to visual cues
• Dorsal lateral geniculate nucleus: relayed to visual cortex (“seeing”)
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Question 2

Where does the optic nerve project to?

Answer 2

Dorsal lateral geniculate nucleus

Question 3

What is the retinal projection to the dLGN characterized by?

Answer 3

The retinal projection to the dLGN is characterized by a retinotopic, point-to-point projection

Question 4

What are features of Retinotopic Maps? (3)

Answer 4

• Visual field maps
• Spatial arrangement of the retina; maintained throughout the visual pathway
• Disproportionate representation

Question 5

Where does the right and left visula field fall on the eye?

Answer 5

Right visual field

• Falls on the right nasal
• Falls on the left temporal

Left visual field

• Falls on the left nasal
• Falls on the right temporal

Question 6

What can result in focal visual loss?

Answer 6

Focal Lesions

Depending on where the focal lesion lies, alters the visual field affected

Question 7

How was it shown that neurons detect orientation? (3)

Answer 7

• Light bar stimulus projected on screen
• Specific stimulus orientation resulted in differences in neurone firing of cat
• Shows how orientation of a stimulus is detected by neurons in the visual cortex

Question 8

What do columns and adjacent columns respond to?

Answer 8

• Columns respond to one direction
• Adjacent columns respond to progressive shifts

Question 9

What do columns detect?

Answer 9

Columns detect different orientations and combine them to form a clear image

Question 10

What are ocular dominance columns?

Answer 10

Stripes of neurons in the visual cortex of certain mammals (including humans) that respond preferentially to input from one eye or the other

Question 11

Where do temporal and nasal pathways fall?

Answer 11

Temporal pathways fall on the ipsilateral side of the visual cortex layer 4

Nasal pathways fall on the contralateral side of the visual cortex layer 4

Question 12

What are Hypercolumns in the visual cortex?

Answer 12

A functional unit formed of the neighbouring columns whose neurons respond to a stimulus of particular orientation