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S2 Neuroscience > Visual System 2 > Flashcards

Visual System 2 Flashcards

1
Q

primary visual pathway

-path of optic nerve fibers from the temporal retina (nasal visual hemifield)

A

course caudally along the lateral edge of the optic nerve, optic chiasm and optic tract to the ipsilateral lateral geniculate nucleus (LGN)

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2
Q

primary visual pathway

-path of optic nerve fibers from the nasal retina (temporal visual hemifield)

A

course caudally along the medial edge of the optic nerve and then cross in the chiasm
after crossing, these fibers course along the medial edge of the optic tract to the contralateral LGN

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3
Q

primary visual pathway

-path of optic nerve fibers from the upper retina (inferior or lower visual hemifield)

A

course caudally along the dorsal edge of the optic nerve, optic chiasm, and optic tract

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4
Q

primary visual pathway

-path of optic nerve fibers from the lower retina (superior or upper visual hemifield)

A

course caudally along the ventral edge of the optic nerve, optic chiasm, and optic tract

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5
Q

topographic arrangement of retinogeniculate fibers carrying information from

  • peripheral visual fields
  • fovea
A 
periphery
-locates most superficially
fovea
-located more internally
all are within the optic nerve, optic chiasm, and optic tract
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6
Q

after optic nerve fibers pass through the chiasm, they continue as the _____ to end where?

A 
continue as optic tract
end primarily (80%) in LGN
20% terminate in the midbrain in or near the superior colliculus
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7
Q

how do the minority of optic nerve fibers that terminate in the midbrain get there?

A

via the brachium of the superior colliculus (BSC)

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8
Q

after optic nerve fibers synapse in the LGN, where do they go and what carries them there

A

thalamocortical axons proceed to primary visual cortex via visual radiations (geniculocalcarine radiations, optic radiations
-these are the efferent fibers leaving the lateral geniculate nucleus and coursing into the primary visual cortex surrounding the calcarine fissure

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9
Q

function of thalamocortical fibers that are carrying optic nerve information

A

carrying visuotopic information to precise regions of primary visual cortex (area 17)

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10
Q

geniculocalcarine fibers

-can carry information from what areas?

A

lower halves of retinae (upper visual hemifields)

upper halves of both retinae (lower visual hemifields)

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11
Q

geniculocalcarine fibers carrying information from the upper halves of both retinae
-where do they go?

A

course directly backward around the lateral ventricle, as part of the internal capsule, to reach the superior bank of the calcarine fissure - cuneus

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12
Q

geniculocalcarine fibers carrying info from the lower halves of the retinae
-where do they go?

A

course forward toward the tip of the temporal horn of the lateral ventricle, then loop inferiorly then caudally in the temporal lobe to reach the inferior bank of the calcarine fissure - lingual gyres

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13
Q

long loop created by the geniculocalcarine fibers carrying info from the lower halves of the retinae is called…
-if injured separately from the other geniculocalcarine fibers, it results in…

A

Meyer’s Loop

results in a contralateral upper homonymous quandrantanopia

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14
Q

primary visual cortex

  • where is the central visual location represented
  • where is the macula represented
  • where are the peripheral visual fields represented
A

central visual field
-most posterior part of the occipital lobe
macula
-represented at the occipital pole
peripheral visual fields
-in rostral direction along the calcarine fissure (ceneus and lingual gyrus)

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15
Q

LGN

  • location
  • composed of how many layers
A

located at the termination of the optic tracts (retinogeniculate fibers) in the thalamus
6 layers

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16
Q

each LGN contains a representation of the _____

A

contralateral visual hemifield

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17
Q

the 6 layers of the LGN are divided into what groups?

-each layer contains a map of the…

A

magnocellular
parvocellular
each layer contains a map of the contralateral visual hemifield

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18
Q

magnocellular layers

  • involved in…
  • which cells carry this information to the LGN
A

involved in perception of dark and light contrast

M-cells, correspond to information from transient ganglion cells that are activated by rods

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19
Q

parvocellular cayers

  • function
  • which cells carry this information to the LGN
A

process fine spatial and color information

P-cells, correspond to information from sustained ganglion cells that are activated by cones

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20
Q

secondary visual pathways

  • where else do axons of retinal ganglion cells project?
  • where is the major secondary projection?
A

project to several areas within the midbrain

major projection is to the superior colliculus

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21
Q

retino-collicular fibers

-travel through ____ to terminate in _____

A

travel through brachium of the superior colliculus to terminate in the superior colliculus

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22
Q

retino-collicular fibers

-after synapsing in the superior colliculus, where do they go?

A

project to the prestriate visual areas that surround primary visual cortex (areas 18 and 19)

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23
Q

secondary visual pathways

  • where do the fibers that do not end in the superior colliculus go?
  • what is the function of these fibers
A

branch off in the brachium of the superior colliculus and terminate in the nuclei of the pretectal area just rostral to the superior colliculus
this connection is the afferent limb of the pupillary light reflex that adjusts pupil diameter specific to amount of light entering the eye

24
Q

secondary visual pathways: fibers responsible for afferent limb of pupillary light reflex

  • connect to…
  • this results in…
A

connect to oculomotor complex

results in constriction of pupil

25
Q

oculomotor complex

-descending connections to T1, T2 intermediolateral cell column control…

A

control dilation of pupil

26
Q

quadrant defects

-often first clue to some pathology where?

A

in “silent” areas of cortex

-especially temporal lobe cortex

27
Q

macular sparing

  • what is it?
  • occurs when…
A

field defects which include everything except macular field (central vision)
occurs when intire ipsilateral visual cortex is destroyed except for the occipital pole

28
Q

in macular sparing, why is the occipital pole spared?

-also, what does the occipital pole represent?

A

receives an overlapping blood supply

represents fovea

29
Q

what are the primary areas in the cortex that respond to visual stimulation

A 
primary visual (striate) cortex (area 17)
secondary and tertiary visual (prestriate) cortex (areas 18 and 19)
30
Q

primary visual cortex

-contains an orderly map of _____, which it receives from neurons of _____

A

map of the contralateral visual hemifield, which it receives from neurons of the LGN

31
Q

primary visual cortex: location of mapping of

  • central visual field
  • peripheral visual fields
A

central
-posterior pole in the occipital lobe
peripheral
-more anterior portions of the calcarine sulcus

32
Q

primary visual cortex

-which area is greatly magnified and occupies a disproportionally large portion of the cortical tissue

A

fovea

33
Q

once information is mapped on the primary visual cortex, where is the information distributed to?
-what is the purpose of sending the information to each of these locations

A 
areas 18 and 19, then to...
temporal lobe
-object recognition
areas in the posterior parietal lobe
-perception of motion
-rotation and depth
parieto-temporal lobe junction
-perception of color
-rotation and depth to a lesser extentr
34
Q

the temporal lobe, posterior parietal lobe, and parieto-temporal lobe are extensively interconnected to allow…

A

perception of visual space (depth and movement)
object specificity (color and form)
within the visual space

35
Q

information derived from p-cells of LGN is responsible for…

A

relaying information on form and color of objects to the temporal lobe regions (P pathway)

36
Q

information derived from m-cells of LGN is responsible for…

A

relaying information concerning gross form and motion to parietal lobal areas (M pathway)

37
Q

lesions of primary visual cortex

-results in…

A

contralateral visual field deficity (visual field cut)

38
Q

if a lesion involves all of area 17 bilaterally

  • what will be gone
  • what may remain?
  • -why might this remain?
A

subject will appear blind
may retain the pupillary light reflex
-thought to reflect collicular function

39
Q

name the other visual areas (outside of primary visual cortex)

A

prestriate (extrastriate) cortex (areas 18 and 19)
posterior half of the middle and inferior temporal gyri
area V5
anterior half of the middle and inferior temporal gyri, Brodmann’s areas 20 and 21
area V3

40
Q

prestriate cortex

  • called the…
  • receives projections from what three sources
A 
visual association cortex
receives projections from
-ipsilateral primary visual cortex
-ipsilateral superior colliculus
-contralateral prestriate cortex
41
Q

visual association cortex lesions

  • severity
  • results in…
A

not as devastating as those in area 17

cause deficits in discriminating between objects or patterns

42
Q

posterior half of the middle and inferior temporal gyri

-receives projections from…

A

prestriate cortex and superior colliculus

43
Q

posterior half of the middle and inferior temporal gyri

-receptive field size compared to striate and prestriate cortex

A

very large receptive fields

44
Q

posterior half of the middle and inferior temporal gyri

-how can these cells be responsive to stimuli from both hemifields

A

receptive fields may extend across the midline

45
Q

posterior half of the middle and inferior temporal gyri

-the fact that receptive fields may extend across the midline indicates…

A

a convergence of information from both hemispheres into this cortical region (i.e. it receives a projection from the contralateral hemisphere)

46
Q

what is the first level of the visual system in which visual stimuli from both hemispheres are merged to form a single image

A

posterior half of the middle and inferior temporal gyri

47
Q

posterior half of the middle and inferior temporal gyri

-bilateral lesion effect

A

leads to considerable difficulty in identifying the salient features of objects or patterns that distinguish them

48
Q

area V5

  • where is this?
  • what pathway?
A

posterior part of the temporal lobe and its junction with the inferior parietal lobe
-includes parts of the superior temporal sulcus
P pathway

49
Q

area V5

-function

A

involved in form and color recognition

part of this region is also involved in movement, especially with respect to translational movements

50
Q

anterior holf of the middle and inferior gyri

  • receives projections from…
  • physiological properties of cells in this area are similar to…
A

receive projections from posterior half of the respective gyri (P pathway)
properties similar to those found in the posterior area, especially form of objects

51
Q

anterior holf of the middle and inferior gyri

-lesions result in…

A

great impairment of ability to recognize a previously seen pattern or object

52
Q

anterior holf of the middle and inferior gyri

-function

A

function in “memorizing” a visual pattern (object recognition)

53
Q

area V3

-where is this

A

posterior parietal lobe

-Brodmann’s area 7

54
Q

area V3

-receives projections from…

A

receives projections from visual association areas (M pathway)

55
Q

area V3

-function

A

involved in ability to identify rotational and directional movements
involved in ability to identify visual spatial orientation, or position of body in space (depth perception)

S2 Neuroscience (25 decks)

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