Visual Pathways and Eye Movements

Question 1

Visual stimuli are ultimately relayed to the primary visual cortex via the thalamus.

The primary visual cortex is aka the _____ cortex, located on the upper and lower banks of the _____ sulcus, which is Brodmanns area _____

Answer 1

Striate; calcarine; 17

Question 2

The visual pathway ends in the primary visual cortex retinotopically. What does this mean for inferior vs. superior visual fields?

Answer 2

Inferior visual fields project above calcarine sulcus

Superior visual fields project below calcarine sulcus

Question 3

The visual association cortex is known as the extrastriate cortex, composed of brodmanns areas ____ and _____ which surround the striate cortex and comprise the rest of the ______ lobe, as well as related parts of the temporal and parietal lobes. It is heavily interconnected with brodmanns area 17.

Answer 3

18; 19; occipital

Question 4

The _____ nucleus also sends targets to the visual association cortex which helps interpret location, motion, form, and color

Answer 4

Lateral geniculate

Question 5

What are 2 visual cortices besides the striate and extrastriate?

Answer 5

Superior colliculus

Pretectal/pretectum area

Question 6

Function of superior colliculus as visual cortex

Answer 6

Spatially directs head movements and visual reflexes

Question 7

2 sources of input to superior colliculus as visual cortex

Answer 7

Retinal input = select fibers from each optic tract bypass the LGN, passing over the medial geniculate nucleus and terminating retinotopically in superior colliculus

Cortical input = cells in Brodmann 17 project to superior colliculus in retinotopic pattern

[also receives some spinotectal/somatosensory and auditory inputs]

Question 8

The prectectum area is a bilateral group of interconnected nuclei located near the midbrain-forebrain junction. What are the 3 input sources for the pretectum as a visual cortex?

Answer 8

Afferent bilateral fibers from the optic tract

LGN and suprachiasmatic nucleus

Question 9

Function of pretectum area as a visual cortex

Answer 9

Pretectal nuclei respond to varying intensities of illuminance, mediating non-conscious behavioral responses to acute changes in light

Question 10

Area that you see when both eyes are fixed in one position

Answer 10

Visual field

Question 11

Within the visual field, the object of attention is focused and centered at the location of ____ and ____

Answer 11

Fovea centralis

Macula lutea

Question 12

The macula lutea is lateral to the ____ ___ which is the region where the retinal axons leave the eye as the optic nerve, and the area where photoreceptors are absent (blind spot)

Answer 12

Optic disk

Question 13

The macula is represented more _______ in the brain, in the region of the occipital pole, while peripheral visual fields are represented more ______

Answer 13

Posteriorly; anteriorly

Question 14

Visual field is subdivided into what 2 zones?

Answer 14

Binocular zone = broad central region seen by both eyes

Monocular zones (R/L) = seen only by corresponding eye

Question 15

Location on the retina that an object in the visual field is projected

Answer 15

Retinal field

Question 16

Divisions of the retinal field

Answer 16

Nasal half (upper quadrant + lower quadrant)

Temporal half (upper quadrant + lower quadrant)

Question 17

Image formed on the retina is inverted in both ____ and _____ dimensions

Answer 17

Lateral; vertical

Question 18

The image formed on the retina is inverted in both lateral and vertical dimensions

For example:
The left half of the visual field forms an image upon the ______ half of the left retina and the _____ half of the right retina

Answer 18

Nasal (right); temporal (right)

Question 19

The 2 optic nerves partially decussate in the optic chiasm. The ___ half of each retina projects to the contralateral optic tract. The ____ half of each retina projects to the ipsilateral optic tract

Answer 19

Nasal; temporal

Question 20

What is the functional purpose of the decussation of the optic nerve?

Answer 20

Depth perception

Question 21

____ ____ = fibers from temporal retina (ipsilateral eye) + fibers from nasal retina (contralateral eye)

Answer 21

Optic tract

Question 22

The optic tract curves posteriorly around the _____ _____ to terminate in the ______ ____ nucleus

Answer 22

Cerebral peduncle; lateral geniculate

Question 23

The lateral geniculate nucleus consists of six layers of ______ fibers which terminate in a precise retinotopic pattern.

The ventral base is formed by incoming optic tract (retinogeniculate) fibers, while the dorsal and lateral borders are formed by the outgoing _____ _____

Answer 23

Myelinated

Optic radiations

Question 24

The lateral geniculate nucleus is subdivided into what 2 layers based on anatomical origin and functional type?

Answer 24

Magnocellular layer = layers 1 and 2 (ventral)

Parvocellular layer = layers 3-6 (dorsal)

Question 25

Describe the magnocellular layer in terms of cell size and source of input

Answer 25

Contains large cells Receives ganglion cell inputs relaying from rods — larger receptive fields and thick, rapidly conducting axons, sensitive to moving stimuli

Question 26

Describe the parvocellular layer in terms of cell size and source of input

Answer 26

Contains small cells Receives ganglion cell inputs relaying from cones — small receptive fields, slower conducting axons, tonically responsive to stationary stimuli, high acuity color vision

Question 27

T/F: Within the 6 layers of the lateral geniculate nucleus, the pattern is the same in each layer. A given point in the visual field is represented by a column of cells extending through all 6 layers

Answer 27

True

Question 28

Note crossed vs. uncrossed, what layers, and ipsilateral vs. contralateral: Ganglion cell axons that arise in the temporal retina are ________ and terminate in layers _____, ____ and _____ of the __________ LGN

Answer 28

Uncrossed; 2, 3, 5; ipsilateral

Question 29

Note crossed vs. uncrossed, what layers, and ipsilateral vs. contralateral: Ganglion cell axons that arise in the nasal retina are ________ and terminate in layers _____, ____ and _____ of the __________ LGN

Answer 29

Crossed; 1, 4, 6; contralateral

Question 30

The right visual field consists of the nasal retina of the right eye and temporal retina of the left eye. The right nasal retina projects to layers ____, _____, and _____ of the ______ LGN. The left temporal retina projects to layers _____, _____, and ____ of the _____ LGN.

Answer 30

1, 4, 6; left 2, 3, 5; left

Question 31

The same point in visual space is represented ____ times — once in each layer of the LGN, located in the same medial-lateral position. Layers also run rostral—> caudal, representing __________ axis

Answer 31

Six; inferior-superior [note that optic tract axons branch in multiple layers even though they arise from the same visual field

Question 32

What are optic radiations?

Answer 32

Large bundle of myelinated fibers extended from secondary neurons of LGN Maintain retinotopic organization, but individual fibers carry info from one eye

Question 33

Optic radiations relay to the ______ cortex

Answer 33

Primary visual (striate)

Question 34

Divisions of optic radiations

Answer 34

Fibers from lower quadrant of contralateral hemifields Fibers from upper quadrant of contralateral hemifields Fibers conveying info from macula and fovea

Question 35

One division of optic radiations: fibers from the lower quadrant of the contralateral hemifields, originates from ______ portion of LGN and arches caudally to pass through the ______ limb of the internal capsule These fibers target the superior bank of the ______ sulcus, on the ______

Answer 35

Dorsomedial; retrolenticular Calcarine; cuneus

Question 36

One division of optic radiations, the fibers from the upper quadrant of the contralateral hemifields, originate from the _______ portion of the LGN. They do not pass directly caudal to the visual cortex, but arch rostrally, passing into the white matter of the ______ lobe to form a broad U-turn called the _____ ____

Answer 36

Ventrolateral; temporal; Meyer’s loop

Question 37

One division of optic radiations, the fibers from the upper quadrant of the contralateral hemifields, originate from the ventrolateral portion of the LGN. They do not pass directly caudal to the visual cortex, but arch rostrally, passing into the white matter of the temporal lobe to form a broad U-turn called the Meyer’s loop. What happens with temporal lobe damage considering this association?

Answer 37

Temporal lobe damage can produce a superior visual field deficit via Meyer’s loop

Question 38

One division of optic radiations, the fibers from the upper quadrant of the contralateral hemifields, originate from the ventrolateral portion of the LGN. They do not pass directly caudal to the visual cortex, but arch rostrally, passing into the white matter of the temporal lobe to form a broad U-turn called the Meyer’s loop. These fibers target the inferior bank of the calcarine sulcus, on the _____ _____

Answer 38

Lingual gyrus

Question 39

One division of optic radiations, the fibers conveying info from the macula and fovea, originate from ______ regions of the LGN and pass to the caudal portion of the visual cortex

Answer 39

Central

Question 40

Voluntary eye movements are controlled by ______ eye fields (area ______) in the posterior portion of the middle frontal gyrus Corticotectal fibers descend to the ______ _____ which will control the ______ of CN III, IV, and VI

Answer 40

Frontal; 8 Superior colliculus; LMN

Question 41

Involuntary eye movements involve the _______ eye fields in the visual association cortex projecting _________ fibers to the superior colliculus — may be associated with following a target

Answer 41

Occipital; corticotectal

Question 42

Lesion of the visual system characterized by blindness in 1/2 of the visual field

Answer 42

Hemianopia

Question 43

Lesion of the visual system characterized by blindness of a quadrant of the visual field

Answer 43

Quadrantanopia

Question 44

Conditions in which visual field losses are similar in both eyes

Answer 44

Homonymous visual fields

Question 45

Conditions in which the two eyes have non-overlapping field losses

Answer 45

Heteronymous visual fields

Question 46

Visual field loss of one eye can be superimposed on that of other eye (symmetrical)

Answer 46

Congruous

Question 47

The closer a lesion is to the visual cortex, the more ______ it is likely to be

Answer 47

Congruous (visual field loss of one eye can be superimposed on that of other eye)

Question 48

The more ______ a lesion is in the optic tract or radiations, the more likely it is that it will be incongruous

Answer 48

Anterior

Question 49

Damage anterior to optic chiasm affects which eye(s)?

Answer 49

Only ipsilateral eye

Question 50

Damage at the optic chiasm causes ________ visual deficits

Answer 50

Heteronymous (the two eyes have non-overlapping field losses)

Question 51

Damage behind the optic chiasm causes _____ deficits

Answer 51

Homonymous (visual field loss similar in both eyes)

Question 52

Condition in which destruction of one optic n. causes blindness in the eye that it arises

Answer 52

Monocuar blindness

Question 53

Condition in which damage to one side of the optic chiasm destrooys noncrossing ipsilateral fibers (arising in temporal retina)

Answer 53

Nasal hemianopia (blindness in nasal half of visual field)

Question 54

Condition arising from damage to the crossing fibers from both eyes at the optic chiasm

Answer 54

Bitemporal hemianopia (one type of heteronymous hemianopia — the two eyes have non-overlapping field losses)

Question 55

Condition caused by destruction of one optic tract

Answer 55

Contralateral homonymous hemianopia

Question 56

Describe the effects of contralateral homonymous superior quadrantopia

Answer 56

Damage to one temporal lobe and/or parts of optic radiation Specific to the contralateral superior quadrant of each visual field [Can also see homonymous inferior quadrantopia]

Question 57

Contralateral homonymous hemianopia is due to damage to one ______ lobe. However, since _____ representation is very large there is _______-sparing

Answer 57

Occipital; macular; macular

Question 58

Condition caused by infarction of the left occipital lobe and posterior corpus callosum, typically secondarily due to occlusion of the posterior cerebral artery

Answer 58

Associative visual agnosia

Question 59

What effect does associative visual agnosia have on a patient?

Answer 59

It disconnects the language area from the visual association cortex, so patient cannot name or describe an object in the visual field but can recognize and demonstrate its use [thus visual perception is intact] Patients may also be alexic and writing ability may be affected