31: Visual Tracts

Question 1

What forms depth perception?

Answer 1

When info from both eyes comes together in the optic tract

Question 2

What are the two types of layers called in the lateral geniculate nucleus?

Answer 2

Magnocellular, parvocellular

Question 3

Four functions of the LGN

Answer 3

1. Controls motion of eyes to converge on point of interest
2. Control focus of eyes based on distance
3. Determine relative position of objects to map them in space
4. Detect movement relative to object

Question 4

What part of the retina takes up a disproportionately large area of the LGN and visual cortex

Answer 4

Macula and fovea

Question 5

Path of optic radiations to the primary visual cortex

Answer 5

Arch rostrally, pass through temporal lobe, make a U-turn as the Meyer loop

Question 6

Other name for visual association cortex

Answer 6

Parietooccipital-temporal area

Question 7

Visual field vs retinal field

Answer 7

Visual field: area a person is able to see when both eyes are fixed in a position
Retinal field: location on retina onto which an objected in the visual field is projected

Question 8

How are images inverted on the retina?

Answer 8

In both lateral and vertical dimensions

Question 9

Where is the left half of the visual field displayed on the retina?

Answer 9

Nasal half of left retina + temporal half of right retina

Question 10

How do quadrants of the visual field project to the primary visual cortex?

Answer 10

Each quadrant projects to its own quadrant of the primary visual cortex

Question 11

Where does the upper left quadrant of the visual field represent in the visual cortex?

Answer 11

Upper left visual field -> lower right visual cortex

Question 12

Another term for depth perception

Answer 12

Stereoscopic vision

Question 13

How are visual system lesions named?

Answer 13

By visual field, not retinal field

Question 14

Hemianopia vis quadrantanopia

Answer 14

Hemianopia: blindness in one half of the visual field
Quadrantanopia: blindness in one quadrant of visual

Question 15

Homonymous visual field vs heteronymous visual field

Answer 15

Homonymous: conditions in visual field loss is similar in both eyes
Heteronymous: conditions where eyes have non-overlapping field loss

Question 16

Macular sparing

Answer 16

Visual field loss that preserves vision in center of visual field

Question 17

Congruous lesions of the optic tracts and radiation

Answer 17

Visual field loss of one eye is superimposed on that of the other eye

Question 18

Lesions are more likely to be congruous when they are in what two areas?

Answer 18

1. Closer to visual cortex

2. More posterior in optic tract/radiation

Question 19

Lesions: anterior to chiasm, at chiasm, and behind chiasm

Answer 19

Anterior to: affects ipsilateral eye
At chiasm: heteronymous deficits
Behind chiasm: homonymous deficits

Question 20

Associative visual agnosia: cause

Answer 20

Infarct of left occipital lobe + posterior corpus callosum, typically from PCA damage

Question 21

What two areas become disconnected in associative visual agnosia

Answer 21

Language area + visual association cortex

Question 22

S/S of associative visual agnosia

Answer 22

Pt cant name or describe an object in the visual field, but can recognize and demonstrate its use; can also be alexic and have agraphia