Central Visual Pathways

Question 1

What are the 3 interneurons in the retina

Answer 1

Bipolar, amacrine, and horizontal

Question 2

What are the only projection neurons int he retina

Answer 2

Retinal ganglion cells

Question 3

What is meant by the horizontal and vertical organization of the retina

Answer 3

Horizontal is inhibitory and vertical is cone, bipolar, retinal ganglion cells

Question 4

What vessels supply the inner and outer portions of the retina

Answer 4

Central artery of the retina=inner and choroidal arteries=outer

Question 5

What are the major refractory structures of the eye

Answer 5

The cornea and the lens

Question 6

What is the difference between the optic nerve and optic tract

Answer 6

In the optic nerve the axons are from one eye only. Int he optic tract there are axons from parts of both eyes

Question 7

What are the 4 main central targets of RGC axons

Answer 7

1. Lateral geniculate nucleus
2. Superior colliculus
3. Pretectum
4. Hypothalamus

Question 8

How is the lataral geniculate nucleus (LGN) involved in the visual pathway

Answer 8

It relays to the cortex for conscious proprioception of vision

Question 9

How is the superior colliculus involved in the visual pathways

Answer 9

It generates eye movements, visual reflexes, and is part of an indirect pathway for the relay of information to the cortex

Question 10

How is the pretectum involved in the visual pathway

Answer 10

It is an area of the midbrain involved in the pupillary light reflex

Question 11

How is the hypothalamus involved in the visual pathway

Answer 11

It is involved in circadian rhythms

Question 12

Where does the LGN lie

Answer 12

In the posterior and lateral part of the thalamus

Question 13

What does each LGN process

Answer 13

Information from he contralateral hemifield of vision

Question 14

What vessels supply the LGN

Answer 14

The anterior choroidal artery and small branches ft he posterior cerebral artery

Question 15

Where do the LGN neurons project

Answer 15

To area 17 via the geniculo-calcarine tract as OPTIC RADIATIONS of the posterior limb of the internal capsule

Question 16

Where do axons coming out of the medial part of the LGN travel

Answer 16

They course dorsally over the lateral ventricle, to the internal capsule, and enter the cuneus gurus of the calcarine cortex

Question 17

Where do axons coming out of the lateral portion of the LGN course

Answer 17

Rostral around the Meyers loop, enter the internal capsule, and project to the lingual gyrus of the calcarine cortex

Question 18

What is the blood supply to the geniculo-calcarine tract

Answer 18

Deep perforating branches of the middle and posterior cerebral arteries, but mainly the middle cerebral artery

Question 19

Optic radiations represent what visually

Answer 19

The contralateral hemifield

Question 20

After entering area 17, area 17 projects to what

Answer 20

Extrastriate visual areas=higher order visual cortical areas int he occipital, temporal, and parietal lobes

Question 21

In order to identify “what” and object is, area 17 projects to where

Answer 21

Extrastriate visual areas of the occipital and temporal lobes

Question 22

In order to identify “where” an object is, area 17 projects to what areas of the brain

Answer 22

Extrastriate visual areas of the occipital and parietal lobes

Question 23

Once RGC’s project to the superior colliculus what are some of the roles it plays with vision

Answer 23

1. Orienting to moving stimuli and directing gaze

2. Relaying information to the cortex via the pulvinar

Question 24

Describe the pathway involving the superior colliculus to the pulvinar from RGC’s

And what is something unique about this pathway

Answer 24

RGC’s–> Superior Colliculus–>Pulvinar(thalamus)–>extrastriate visual cortex

It does not pass through area 17, it goes straight to the extrastriate visual cortex

Question 25

Lesions of area 17 result in what clinically

Answer 25

Someone who is functionally blind, but these people can still see light or it can be perceived. They are not AWARE that they are seeing

Question 26

Individuals with a bilateral destruction of the occipital lobes results in what clinically

Answer 26

An individual denies they are blind, but they are

Question 27

Visual agnostic is a result of what

Answer 27

Lesions of higher order visual areas with area 17 still being in tact

Question 28

Prosopagnosia

Answer 28

The inability to match a face with its identity

Question 29

Where is the pulvinar located

Answer 29

The dorsal thalamus