Fusion, Rivalry, and Suppression Flashcards Preview

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Flashcards in Fusion, Rivalry, and Suppression Deck (41)
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1
Q

where does fusion happen in the brain

where do we stop seeing monocularly in the brain

A

fusion happens in the visual cortex

stop seeing mono in layer 4C of the striate cortex

2
Q

what are the 2 parts of fusion process

A
  1. sensory: images near corresp points are fused

2. motor: move eyes in or out to fuse images at diff distances

3
Q

what are the 2 types of diplopia, which is abnormal

A

physiological: nonfixated objects off the horopter
pathological: seeing 2 of the image you are paying attentino to, NOT NORMAL

4
Q

what is confusion
where is it most visible in
what does it usually accompnay
another name?

A

when you perceive 2 diff objects to be in the exact same place in the vf

  • most visible in foveal vision
  • usually accompanies diplopia
  • aka binocular rivalry
5
Q

what is panum’s area

A

an area on the retina of one eye wehre an image may be placed and still fuse w/ an image at a fixed location in the fellow eye

6
Q

what is panum’s space

A

the region of 3D space where singleness is perceived

7
Q

do all points fused in panum’s area appear in the same location in visual space

A

no-each diff pair of retinal points in PA creates a unique stereo depth and direction in visual space so there is no loss of spatial info w/ fusion

8
Q

where is the horopter in panum’s space

A

in the middle

9
Q

what is allelotropia

A

the oculocentric directions of fused images are averaged to form a cyclopean direction
-direction averaging process is influenced by ocular dominance

10
Q

how is PA related to retinal eccentricity

A

PA size increases w/ retinal eccentricity

11
Q

when patients report diplopia, where is it usually from

A

foveal

-it is not easily observed in peripheral vision

12
Q

how does PA change in the periphery

A

increases as you move out to the periphery

13
Q

what kind of motion increase the size of PA

A

target motion and patient motion

14
Q

higher spatial freq (sharp edges) are associated w/ ____ PA size

A

smaller

15
Q

what are the various sizes taht have been reported for foveal panum’s area?
using what kind of things?

A

2’ (woo, using fine bars)
6’ (ogle, using horopter rods)
15’ (mitchell, using small flashing spots)

16
Q

how is PA shaped for very brief stimuli?
how is it shaped for long duration stimuli?
how is it shaped for static targets?
how is it shaped for foveal?

A
  • round for brief
  • PA diamter slightly increased vert and greatly increased horiz (3x) for long duration
  • horizontal ellipse for static
  • elliptical for foveal
17
Q

how is panum’s area is strabismic patients

A

most constant strabismus have no fusion or panum area

18
Q

why do patients w/ microtropia have single peripheral vision

A

-ocular misalignment is too large in microtropes to allow images to fall w/in normal panum’s area in the foveal macular area

19
Q

how does PA develop in pts w/ constant microtrope strab

A

very large panum’s areas in the periphery

20
Q

what is binocular summatino

A

a change of nonspatial quality of vision caused by binocular interaction

21
Q

what are the possible levels of mathematical binocular summation

A
  1. facilitation: when stimulus is more than twice as bright OU than w/ one eye. 1+1>2
  2. complete summation: when stimulus is twice as bright OW
    1+1=2
  3. partial summation: when stimulus is brighter OU
    1+1=1.5
  4. zero summation: when stimulus is as bright OU
    1+1=1
  5. inhibition: when stimulus is not as bright OU
    1+1<1
22
Q

what is most binocular summation in terms of math

A

zero summation or partial summation

23
Q

how do eyes behave for dim scotopic images falling outside panum’s area

A

weak stimuli more detected w/ 2 eyes than 1 bc you get 2 changes of detection

24
Q

how is binocular summation related in CFF, contrast threshold, and resolution threshold

A

CFF: goes up
contrast threshold: goes down
resolution threshold: goes down bc of contrast threshold

25
Q

how are small differences in luminance and large difference in luminance handled by the brain

A

small: averaged by the brain
large: not averaged and the dimmer eye is suppressed

26
Q

what is color luster

A

for small differences of color btwn the 2 eyes image, we average them

27
Q

what color does the eye end to see more w/ brighter luminance? dimmer luminance?

A

brighter: eye tends to see things more towards blue
dimmer: eye tends to see images more toward red

28
Q

what does the eye do for large differences btwn colors of the 2 eyes

A

we do not average them
we will see rivalry (see one color then it turns into another, then back to the first)
-rate of alternation is dependent on luminance

29
Q

what is interocular transfer

when does this happen

A

binocular vision ells get adapted to a pattern when looking at another pattern and maysee an aftereffect which affects the new pattern
-happens w motion (waterfall effect), tilt, and size

30
Q

when does suppression occur

when does amblyopia occur

A

suppression=BINOCULAR VISION, momentary thing

amblyop=monocular vision

31
Q

what is physiological suppression

A

a normal form of suppression associated w/ non-horopter objects

  • when very dissimular images fall on corresponding points and brain can’t fuse
  • when images are of equal contrast, the perosn will perceive these images to be alternating
32
Q

what is binocular rivalry

A

2 diff images to the eyes but of equal contrast and importance and sitmulated corresponding points
-brain will go back and forth btwn which image is perceived

33
Q

if binocular rivalry occurs in foveal vision, the patient will report what

A

confusion

34
Q

is rivalry noticed in peripheral vision?

A

rarely

35
Q

what are rivalry suppression scotomas

  • how are they shaped
  • what is there size in panum’s area
A

regions in the monocular field where the suppression (from rivalry) is occurring

  • always round
  • twice as large in panum’s area at the same retinal location
  • larger in periphery
36
Q

when is pathological suppression found

A

early onset binocular abnormalities

-ARC patients

37
Q

what is pathological suppresion

which eye does it occur

A

suppresion induced by stimulus conditions which cause fusion in normals: similar images on corresponding points
-non dominant eye

38
Q

does adult onset strab cause pathological suppression?

A

no. causes diplopia w/o it

39
Q

what is a clinical test of suppresion

A

worth 4 dot test
-underestimates suppression in normal viewing though bc darkness, absence of textured background, red/green glasses (promotes rivalry) weakens suppression

40
Q

how are pathological suppression and rivalry related

A

both are stronger for images on corresponding points than noncorresponding points
-image dissimilarity on corresponding points may induce rivalry in both normals and strabs

41
Q

at minimum, what is the scotomoa size for pathological suppression scotomas

A

at min the fovea and zero-measure points