wk3: ND - Visual development and Amblyopia Flashcards

1
Q

True/False: afferent pathways from the two eyes remain segregated as they project to the visual cortex

A

True

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2
Q

Describe research by Hubel and Wiesel, 1977, that stated Monocular deprivation leads to ocular dominance shift

A

In cats and monkeys you have a range of monocular/binocular cells, driven by 7 categories:
group 1 = only contralateral eye, group 4 = equal input, group 7 = only ipsilateral eye

Response (total number of cells reponding) for each group of these monocular/binocular cells in area 17 were measured after monocular deprivation (suturing of an eye) and they found what the title said

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3
Q

In Hubel’s monocular deprivation study, how did they look at the eye?

A
  1. Adult monkey: radioactive aminoacid injected into ipsilateral eye
    2 and 3. 18 month old monkeys: one eye sutured at 2 weeks
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4
Q

What did anatomical observation by Hubel in his monocular deprivation experiment find?

A

Anatomical studies show layer IV dominated by non-deprived eye, i.e., the non-deprived eye takes over most of the available cortical space

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5
Q

What happens when you suture both eyes shut? (Binocular deprivation)

A

Binocular Deprivation causes only fewer binocular cells. Receptive fields are not very abnormal! [In Nicholls, p. 560]
! !

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6
Q

What did Levay et al 1978 find about cat ocular dominance? How did he do this?

A

Found that cat ocular dominance is column dependant. He injected radioactive aminoacid into the ipsilateral eye at different postnatal days: at 2 weeks the whole of layer 4 of the striate cortex is filled with the radioactive label, whereas less and less of layer 4 is filled, as gaps start to appear as more time passes

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7
Q

What is interesting about LGN afferents terminating in layer 4 of the striate cortex?

A

they have markedly overlapping arbors

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8
Q

In cats and monkeys, when do distinct ocular dominance patterns become evident in layer 4 of the striate cortex?

A

Within about 6 weeks

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9
Q

Define arbor/arborization

A

a treelike figure or arrangement of branching parts especially : a treelike part or process (as a dendrite) of a nerve cell the terminal arborization of an axon. Comments on arborization.

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10
Q

What happens to geniculocortical axon arbors in the deprived eye of a cat with a deprived eye?

A

Much more shallow (way less branches) and much less concentrated. Barely any inputs here and the inputs are way less dense compared to the normal eye

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11
Q

True/False: There is competition between the geniculocorticoid inputs related to the two eyes for cortical space

A

True

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12
Q

Which vision is essential to establish normal connectivity? Form vision or Diffuse Light?

A

Form vision

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13
Q

What happens to cortical inputs in the one eye in the absence of inputs from the other eye?

A

Inputs increase. Inputs related to the other eye takes over the cortical space

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14
Q

What is the critical period for humans to be susceptible to ocular dominance shifts? Can ocular dominance shifts occur outside this period?

A

Few years. Yes they can, but obviously less likely

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15
Q

Does the extent of critical period for susceptibility for ocular dominance shifts differ between species?

A

Yes

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16
Q

Do different visual functions (e.g. stereopsis, contrast sensitivity, face recognition) have different critical periods?

A

Yes

17
Q

Define Occlusion Amblyopia

A

e.g., when one eye is occluded by a congenital cataract or a lid ptosis

18
Q

Define anisometropic amblyopia

A

when the two eyes have very different refractive errors

19
Q

Define strabismic amblyopia

A

when one eye is deviated (eye turn, squint).

20
Q

Provide 2 reasons for poor visual acuity in infants

A

(note: it is NOT due to poor optics)
All cone fovea contains widely spaced and poorly developed cones
Visual cortex not fully developed