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Neuroscience > L28 Visual Pathways > Flashcards

L28 Visual Pathways Flashcards

1
Q

define hemianopia

A

visual loss in 1/2 of the visual field (visual hemifield)

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2
Q

define quadrantic anopia

A

visual loss in 1/4 of the visual field

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3
Q

define homonymous anopia

A

same visual field defect for both eyes

left visual field (temporal) is affected in L eye
left visual field (nasal) is affected in R eye

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4
Q

define heteronymous anopia

A

different visual field defect for both eyes

example - visual loss affecting the temporal visual field in either eye (bitemporal hemianopia) –
left visual field (temporal) in L eye
right visual field (temporal) in R eye

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5
Q

what is the visual field

A

the total space seen when the eye is fixed looking straight ahead towards the center of the visual field (point of fixation)

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6
Q

what is another name for left and right hemifields? what is their span?

A

nasal and temporal fields

60-90 degrees (nasal to temporal)

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7
Q

the superior half of the visual field is reflected onto the _____ half of the retinal field

A

inferior + vice versa (upside down)

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8
Q

the nasal half of the visual field is reflected onto the _____ half of the retinal field

A

temporal + vice versa (opposite)

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9
Q

in summary, how do the visual fields reflect on the retinal field?

A

upside down

and opposite

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10
Q

what is the projection pathway of retinal ganglion cells?

A

retinal ganglion cells –> optic disk –> optic nerve –> optic chiasm –> LGN (thalamus) –> primary visual cortex V1

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11
Q

where is the macula located in the visual field diagram?

A

in the center

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12
Q

images from the superior visual field will travel via the _______ to the ____ portion of V1

A

temporal radiation

inferior

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13
Q

images from the inferior visual field will travel via ____ to the ____ portion of V1

A

parietal radiation

superior

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14
Q

images from the LEFT visual field will relay to the ___ LGN and then to the ____ portion of V1

A

right

right

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15
Q

images from the RIGHT visual field will relay to the ____ LGN and then to the ____ portion of V1

A

left

left

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16
Q

what are the 4 places that retinal ganglion cells can terminate?

A 
LGN (thalamus)
suprachiasmatic nucleus (hypothalamus)
pretectal nucleus (midbrain)
superior colliculus (midbrain)
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17
Q

what is the role of the LGN

A

relay station between the retina and the primary visual cortex

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18
Q

what is the role of suprachiasmatic nucleus?

A

trigger circadian clock

19
Q

what is the role of the pretectal nucleus

A

forming part of the afferent limb of the pupillary light reflex

20
Q

what is the role of the superior colliculus

A

contribute to eye movements

21
Q

What Brodmann’s area corresponds to the primary visual cortex?

A

Area 17 (superior and inferior gyrus split by calcarine sulcus)

22
Q

where is a major portion of the primary visual cortex represented

A

on the medial aspect of the brain

23
Q

where does the primary visual cortex receive most of its blood supply?

A

calcarine branches of the PCA

*note - small portion around occipital pole may also get blood from MCA (especially after an occlusion of the PCA)

24
Q

retinoptic organization of V1: the left visual fields reflects to the ____ V1

A

right V1 (vice versa)

25
Q

retinoptic organization of V1: the superior visual fields reflects to the ____ V1

A

inferior (vice versa)

26
Q

retinoptic organization of V1: the macular/central vision reflects to the _____ V1

A

superficial

27
Q

retinoptic organization of V1: the peripheral vision reflects to the ____ V1

28
Q

what types of columns make up the columnar organization of V1

A

occular dominance columns

orientation columns

29
Q

describe occular dominance columns

A

there are separate/infividual areas (column) dedicated to the input from each eye

there are contralateral columns (C) and ipsilateral columns (I) in both the left and right V1

*visual fields from both the L and R eye can relay to a single side of V1, however that info does not actually reach identical locations

30
Q

describe orientation columns

A

there are columns of V1 that have a preference to the orientation of the image in the visual field

there are various orientation columns which have varying preferences such as vertical and horizontal light as well are the intermediate variations!

31
Q

what layers of the cortex are involved in the organization of columns?

A

all of them
layer 1 near pial surface
layer 6 near white matter

32
Q

what are depth, motion, form and color handled

A

parallel pathways

33
Q

what is the pathway for depth and motion

A

magnocellular neurons (M-ganglion cells) of the retina –> synapse in 2/6 layers in the LGN –> follow dorsal (parietal pathway)

note - similar to inferior visual field

34
Q

what is the pathway for form and color

A

start in parvocellular neurons (P-ganglion cells) of the retina –> synapse in 4/6 layers in the LGN –> follow ventral (temporal) pathway

note - similar to superior visual field

35
Q

what is the confrontational visual field test

A

each quadrant of the visual field can be tested individually

36
Q

site of lesion: optic n.
what is the visual field defect?
what is the possible origin?

A

visual field defect: monocular blindness

what is the possible origin: optic neuritis

37
Q

site of lesion: optic chiasm
what is the visual field defect?
what is the possible origin?

A

visual field defect: bitemporal hemianopia

what is the possible origin: pituitary tumor

38
Q

site of lesion: optic tract
what is the visual field defect?
what is the possible origin?

A

visual field defect: homonymous hemianopia

what is the possible origin: temporal lobe tumor

39
Q

site of lesion: temporal radiation (Meyer’s loop)
what is the visual field defect?
what is the possible origin?

A

visual field defect: homonymous superior quadrantic anopia

what is the possible origin: temporal or occipital lobe tumor

40
Q

site of lesion: parietal radiation
what is the visual field defect?
what is the possible origin?

A

visual field defect: homonymous inferior quadrantic anopia

what is the possible origin: parietal or occipital lobe tumor

41
Q

site of lesion: visual cortex
what is the visual field defect?
what is the possible origin?

A

visual field defect: homonymous hemianopia

what is the possible origin: PCA dysfunction

42
Q

what is color agnosia (achromotopsia)?

A

inability to distinguish colors due to cortical lesions in areas 18 and 37 = cortical color blindness

43
Q

what are the sensory cortex generalizations

A

topographical organization - retinotopic map
organization in columns - occular dominance and orientiation columns
input layer IV - thalamocortical fibers from LGN end here

Neuroscience (54 decks)

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