Fusion, Rivalry, and Suppression

Question 1

where does fusion happen in the brain

where do we stop seeing monocularly in the brain

Answer 1

fusion happens in the visual cortex

stop seeing mono in layer 4C of the striate cortex

Question 2

what are the 2 parts of fusion process

Answer 2

1. sensory: images near corresp points are fused

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

Question 3

what are the 2 types of diplopia, which is abnormal

Answer 3

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

Question 4

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

Answer 4

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

Question 5

what is panum’s area

Answer 5

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

Question 6

what is panum’s space

Answer 6

the region of 3D space where singleness is perceived

Question 7

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

Answer 7

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

Question 8

where is the horopter in panum’s space

Answer 8

in the middle

Question 9

what is allelotropia

Answer 9

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

Question 10

how is PA related to retinal eccentricity

Answer 10

PA size increases w/ retinal eccentricity

Question 11

when patients report diplopia, where is it usually from

Answer 11

foveal

-it is not easily observed in peripheral vision

Question 12

how does PA change in the periphery

Answer 12

increases as you move out to the periphery

Question 13

what kind of motion increase the size of PA

Answer 13

target motion and patient motion

Question 14

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

Answer 14

smaller

Question 15

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

Answer 15

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

Question 16

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?

Answer 16

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

Question 17

how is panum’s area is strabismic patients

Answer 17

most constant strabismus have no fusion or panum area

Question 18

why do patients w/ microtropia have single peripheral vision

Answer 18

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

Question 19

how does PA develop in pts w/ constant microtrope strab

Answer 19

very large panum’s areas in the periphery

Question 20

what is binocular summatino

Answer 20

a change of nonspatial quality of vision caused by binocular interaction

Question 21

what are the possible levels of mathematical binocular summation

Answer 21

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

Question 22

what is most binocular summation in terms of math

Answer 22

zero summation or partial summation

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

what is color luster

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

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

Question 29

what is interocular transfer

when does this happen

Answer 29

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

Question 30

when does suppression occur

when does amblyopia occur

Answer 30

suppression=BINOCULAR VISION, momentary thing

amblyop=monocular vision

Question 31

what is physiological suppression

Answer 31

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

Question 32

what is binocular rivalry

Answer 32

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

Question 33

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

Answer 33

confusion

Question 34

is rivalry noticed in peripheral vision?

Answer 34

rarely

Question 35

what are rivalry suppression scotomas

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

Answer 35

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

Question 36

when is pathological suppression found

Answer 36

early onset binocular abnormalities

-ARC patients

Question 37

what is pathological suppresion

which eye does it occur

Answer 37

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

Question 38

does adult onset strab cause pathological suppression?

Answer 38

no. causes diplopia w/o it

Question 39

what is a clinical test of suppresion

Answer 39

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

Question 40

how are pathological suppression and rivalry related

Answer 40

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

Question 41

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

Answer 41

at min the fovea and zero-measure points