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Vision Science 2 > 1 - Neurophysiology of Binocular Vision > Flashcards

1 - Neurophysiology of Binocular Vision Flashcards

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1
Q

What is binocular single vision?

A

The ability to use both eyes together to form a single image

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2
Q

What are 3 advantages of binocular vision?

A
  1. Increased visual field
  2. Binocular summation
  3. Stereopsis
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3
Q

Give a brief definition of binocular summation

A

2 eyes are better than 1

VAs are better binocular than monocular

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4
Q

Give a brief definition of stereopsis

A

Sensation of depth due to retinal disparity

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5
Q

What are 5 prerequisites for binocular single vision?

A
  1. Normal visual pathways, overlapping monocular VFs.
  2. Binocular neurons
  3. Normal retino-cortical correspondence
  4. Normal oculomotor system
  5. Equal image size and clarity
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6
Q

What is the visual pathway (retino-geniculate-striate)?

A
  1. Retina
  2. Optic nerve
  3. Optic chiasm
  4. Optic tract
  5. Dorsal Lateral Geniculate Nucleus
  6. Optic radiations (formed by dLGN axons)
  7. Striate cortex (V1 or primary visual cortex)
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7
Q

What would result from complete decussation at the optic chiasm?

A

There would be minimal overlap of monocular VFs and therefore no stereopsis (there actually is still coarse stereopsis supported by the corpus callosum)

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8
Q

Which LGN layers receive input from the IPSILATERAL eye?

A

Layer 2
Layer 3
Layer 5

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9
Q

Which LGN layers receive input from the CONTRALATERAL eye?

A

Layer 1
Layer 4
Layer 6

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10
Q

Which layers of the LGN receive input from the PARVOCELLULAR pathway?

A 
The four dorsal layers
Layer 3
Layer 4
Layer 5 
Layer 6
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11
Q

Which layers of the LGN receive input from the MAGNOCELLULAR pathway?

A

The two ventral layers
Layer 1
Layer 2

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12
Q

Where do the PARVO layers of the LGN project to in the primary visual cortex?

A

Layer 4-C-beta

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13
Q

Where do the MAGNO layers of the LGN project to in the primary visual cortex?

A

Layer 4-C-alpha

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14
Q

Which stream carries MAGNO input, and ends in the posterior parietal cortex?

A

Dorsal stream

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15
Q

Which stream carries PARVO input, and ends in the inferotemporal cortex?

A

Ventral stream

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16
Q

What type of information does the dorsal stream carry, and where does it carry to?

A

MAGNO input

ends in posterior parietal cortex

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17
Q

What type of information does the ventral stream carry, and where does it carry to?

A

PARVO input

ends in infero-temporal cortex

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18
Q

Do cells in each layer of the LGN have monocular or binocular fields?

A

Monocular receptive fields

each individual layer only has input from one eye

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19
Q

Where is the fovea represented in retinotopic mapping of the LGN?

A

Centrally and posteriorly

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20
Q

Where is the peripheral field represented in retinotopic mapping of the LGN?

A

Laterally and anteriorly

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21
Q

Where is the inferior visual field represented in retinotopic mapping?

A

Superiorly

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22
Q

Where is the superior visual field represented in retinotopic mapping?

A

Inferiorly

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23
Q

What type of response do LGN neurons show when stimulated binocularly?

A

Modulated response
mostly inhibitory
may play role in suppression/rivalry

24
Q

What is a modulated response?

A

A response that either enhances or suppresses

25
Q

How much of the striate cortex is used for the central 10 degrees of visual field?

A

More than 50%

fovea is overly represented in V1

26
Q

In what layer do LGN neurons synapse in the striate cortex?

A

Layer IV

27
Q

Are the striate cortical neurons that receive geniculate input monocular or binocular?

A

Completely monocular

28
Q

Where are true binocular neurons located in the striate cortex?

A 
Layer 1
Layer 2
Layer 3
LAYER 4 HAS MONOCULAR NEURONS
Layer 5
Layer 6
29
Q

What are 3 traditional methods of studying binocularity?

A
  1. Single-unit recording
  2. Voltage sensitive dyes
  3. PET/ fMRI scans
30
Q

What is single-unit recording also known as?

A

Extracellular recording

31
Q

What are 3 characteristics of binocular neurons?

A
  1. Have receptive fields in both eyes
  2. Show modulated response to binocular stimulus
  3. Can show facilitation, summation or inhibition depending on the sum of monocular stimuli
32
Q

What are groups of neurons that receive input from the same eye?

A

Ocular dominance columns

33
Q

What is a hypercolumn?

A

Cortical unit that includes a full complement of ocular dominance columns and orientation columns

34
Q

What is a benefit of having retinal disparity?

A

Gives the ability to see depth due to small positional differences

35
Q

What is the horopter?

A

The locus of all points in space that fall on corresponding retinal elements

36
Q

What are disparity detectors?

A

Binocular neurons in the visual cortex sensitive to disparity

37
Q

What type of cells are most responsive to zero retinal disparity?

A

Tuned cells

38
Q

What type of tuned cells are most responsive to targets on the horopter?

A

Tuned excitatory cells

39
Q

What type of tuned cells are most responsive to cells off the horopter?

A

Tuned inhibitory cells

40
Q

Are near and far cells tuned or untuned?

A

Untuned

41
Q

What type of disparities do near cells respond to?

A

Crossed

42
Q

What type of disparities do far cells respond to?

A

Uncrossed

43
Q

What types of cells form the basis for coarse stereopsis (motion stereopsis)?

A

Near cells

Far cells

44
Q

What types of cells form the basis for fine stereopsis (static stereopsis)?

A

Tuned excitatory cells

Tuned inhibitory cells

45
Q

What types of stimuli does fine stereopsis respond to?

A

Small disparities (2 arcsec to 20 arcmin)
High spatial frequencies (>3 cycles per degree)
Low temporal frequencies (stationary/slow moving)

46
Q

What types of stimuli does coarse stereopsis respond to?

A

Large disparities (30 arcmin to 10 degrees)
Low spatial frequencies
High temporal frequencies

47
Q

What is the latency for fine stereopis?

A

250 milliseconds

48
Q

What is the latency for coarse stereopsis?

A

125 milliseconds

49
Q

What are 2 characteristics of the secondary visual cortex (V2)?

A
  1. Large receptive fields

2. Many disparity detectors

50
Q

What are 3 features of V2 revealed with cytochrome oxidase staining?

A
  1. Thick stripes
  2. Thin stripes
  3. Interstripes
51
Q

What type of input do the thick stripes of V2 receive from layer 4B of V1?

A

MAGNO input

52
Q

What type of input do the thin stripes of V2 receive from blob and interblob regions of V1?

A

PARVO input

53
Q

Do interstripe neurons show sensitivity to disparity at high or low spatial frequencies?

A

High spatial frequencies

54
Q

In area V4, what type of input is used for disparity processing?

A

Magnocellular and Parvocellular information

Both inputs are used, different from other functions

55
Q

How do we have stereopsis at the center of the visual field?

A

There is a merging of the two visual fields, rather than a strict split at the midline

56
Q

What structure in the brain allows stereopsis at the midline even if the optic chiasm is damaged?

A

Corpus callosum

Myelinated nerve fibers connecting L and R cerebral hemispheres

57
Q

What type of stereopsis does the callosal pathway support?

A

Coarse stereopsis

Vision Science 2 (6 decks)

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