Binocular Vision: Lecture 12: Binocular Rivalry

Question 1

1. How does the Visual System Handle the Conflicting Information at the Corresponding Points?

Answer 1

1. They either IGNORE or TUNE off Either all or Part of the IMAGE to ONE EYE!

Question 2

1. What is this: 2 DIFFERENT Objects are perceived as occupying the SAME Location in Visual Space.

Answer 2

BINOCULAR CONFUSION

Question 3

1. What is this: a Failure to allow some monocular portion of the Binocular Field to Contribute to the Combined Binocular Perception.
   a. This region undergoes a REDUCTION of sensitivity to what?
   b. With an ELEVATION of what?
   c. How long can it take for this to start?

Answer 3

1. SUPPRESSION
   a. to Visual Stimuli
   b. of Light Detection threshold and Prolongation of Reaction Times
   c. can take up to 75-150 ms for Suppression to begin

Question 4

1. An important Consequence of MISALIGNMENTS of the Visual Axes is that what Can be formed on Corresponding Points?

Answer 4

DISSIMILAR IMAGES

Question 5

1. When Does Binocular Suppression start?

Answer 5

1. When Dissimilar Contours or Features are Presented to Each Eye

(So like a line seen in the left eye going from bottom to top and in right eye going from top to bottom)…when trying to fuse, binocular suppression occurs, so only one of them is seen.

Question 6

1. When a Left eye sees a horizontal line and the Right eye sees two vertical lines, what happens when it tries to fuse the two images together?
   a. So if the two vertical lines look whole, what is happening?

Answer 6

1. When the 2 images are Superimposed, Part of one Eye’s View disappears!
   a. Local Suppression of the Left Eye’s information has occurred.

Question 7

Suppression

1. If both eyes are equal in their contribution to the binocular visual system (1 eye isn’t very dominant over the other), the eye presented with what will be suppressed?
2. Pathological Suppression is usually an adaptation to what?
   a. The visual system over a period of time does what?
3. With strabismus, which eye is dominant?
   a. Which one will be suppressed?
   b. Alternating Strabismics can do what?

Answer 7

1. the Weaker or Less Salient Image
2. to Prolonged Diplopia or Binocular Confusion
   a. “Shuts off” one eye’s image to yield single vision
3. the Fixating Eye
   a. the Nondominant Deviating Eye
   b. can switch eye dominance, so that the formerly deviating eye is now the Fixating Eye and Vice Versa

Question 8

Binocular Rivalry (1)

1. Suppression may also be triggered by dissimilar Binocular inputs. This is called…
   a. This is basically an Intermittent and Alternating Suppression of what?
   b. When does it usually occur?
   c. When is it strongest?

Answer 8

1. Binocular Rivalry
   a. of Brightness, Color, and/or Contour of one, then the other eye.
   b. with Vastly dissimilar images in each eye.
   c. when dissimilar contours are presented, like Orthogonally oriented gratings (gratings rotated at a 90 degree angle relative to each other) imaged in each eye.

Question 9

Binocular Rivalry (2)

1. Rivalry is also more likely to occur when Orthogonally oriented gratings are both of what Contrast?
2. IF the dissimilar targets are small in AREA, each eye’s entire image of the target may be ALTERNATIVELY SUPPRESSED. What is this called?

Answer 9

1. MEDIUM to HIGH CONTRAST

2. EXCLUSIVE DOMINANCE

Question 10

Rivalry:

1. The effect of Contrast on what?
2. The effect of SIZE on what?
3. Rivalry Waves

Answer 10

1. on PREDOMINANCE
2. on FRAGMENTATION
3. Free-fuse pairs of gratings (diverse so that your R and L eyes fixate the right and left gratings respectively)…take time to see if you can observe a “Wave” of dominance moving around the stimulus.

Question 11

1. The binocular Percept is that of a PATCHWORK in which the contours continuously Change over time. What is this called?
2. At any given location, the percept alternates from that of the left eye’s image alone to that of the right eye’s alone, and so on with what happening?

Answer 11

1. MOSAIC DOMINANCE

2. with the AREAS of ALTERNATION CONSTANTLY SHIFTING

Question 12

Binocular Rivalry (2)

1. These independent areas of ALTERNATION have been Called what?
   a. They have been shown to be what in size to the Portion of the VF processed by a CORTICAL HYPERCOLUMN?
   b. The size of a Spatial Zone of Binocular Rivalry will Increase/Decrease as more peripheral portions of the VF are Stimulated by RIVALROUS Stimuli?

Answer 12

1. SPATIAL ZONES of BINOCULAR RIVALRY
   a. to by SIMILAR in size.
   b. INCREASE

Question 13

Binocular Rivalry (3)

1. When a portion of the VF is suppressed in one eye’s image during rivalry, what happens to the SENSITIVITY of that region?
2. The strength of inhibition is typically what?
   a. How high of an elevation in detection threshold is there for stimuli presented to the Suppressed eye due to inhibition?
3. The Strength of Rivalry was Specific to particular locations in the field at which what is present?
   a. But not specific to what?

Answer 13

1. it’s INHIBITED or REDUCED
2. 0.5 LOG UNITS
   a. there’s a THREEFOLD ELEVATION in detection threshold
3. at which Conflicting Stimuli are Present
   a. to the precise characteristics of the stimuli being detected

Question 14

Binocular Rivalry (4)

1. Recent studies suggest that what stimuli are suppressed to a greater extent than what stimuli?
2. The Degree of Inhibition is increased/decreased/remains the same during the period of suppression?

Answer 14

1. Chromatic Stimuli; Achromatic Stimuli

2. Remains the Same

Question 15

Binocular Rivalry (5)

1. What kind of stimulus is LESS LIKELY to be suppressed during rivalry?
2. How might 2 gratings of Equal contrast but Orthogonal Orientations may be perceived?

Answer 15

1. a VISUALLY STRONGER STIMULUS! (it will be visible a greater proportion of the time than will a weaker stimulus)
2. May be perceived ALTERNATELY, w/each eye’s view visible 50% of the time and suppressed 50% of the time

Question 16

Binocular Rivalry (6)

1. What happens if a High contrast grating is shown to one eye, and a low-contrast grating is shown to the other eye?

Answer 16

1. The high contrast grating is perceived MORE THAN 50% of the TIME. and Low contrast grating is seen less than 50% of the time.

Question 17

Suppression vs. Rivalry (1)

1. Suppression and Rivalry differ in what?
2. In Binocular Rivalry, the Percept does what?
3. The Strength of a Suppressed stimulus can still modulate what?

Answer 17

1. in the Rate of Change of Visibility of the Targets in each eye.
2. continually changes from MOMENT to MOMENT at EACH LOCAL AREA as a result of Alternation of Suppression b/w the 2 Eyes.
3. the Period of Time for which that stimulus is suppressed. (the length of its suppression period)

Question 18

Suppression vs. Rivalry (2)

1. A Sudden change in what 3 things may terminate the period of Suppression and Make that Image Available to Perception?
2. Rivalry requires that the images are what b/w the 2 eyes?
3. Suppression, Esp. Pathological Suppression, can still occur when the stimuli are what?

Answer 18

1. in Orientation, Spatial Frequency, or Contrast.
2. DIFFER in the 2 eyes.
3. Can still occur when Identical Stimuli are Presented to EACH EYE

Question 19

Suppression vs. Rivalry (3)

1. When does suppression in Binocular Rivalry tend to be stronger: In normal Binocular Rivalry, or in that of Pathological Suppression found in Strabismus?
2. We Get selective Inhibition of what to a greater degree than to what during binocular Rivalry?
3. Binocular Rivalry and Strabismic Suppression Reflect DISTINCT what?

Answer 19

1. Normal Binocular Rivalry suppression tends to be stronger
2. with Chromatic Channels than w/Achromatic Channels
3. Distinct Neural Processes

Question 20

1. Onset time of Pathological suppression in the Normal Visual System?
   a. Compared to Physiological Suppression?
2. One eye may in fact see part of the More distant object that is occluded from what?
   a. This leads to a rivalrous percept caused by images of the Occluding Near object and part of the occluded distant object being formed on what?

Answer 20

1. MUCH SLOWER ONSET TIME (can take as long as 1-2 minutes)
   a. SHORT. (less than 200 ms)
2. from the other eye’s image.
   a. on corresponding points.

Question 21

Binocular Rivalry (6?)

1. In DICHOPTIC MASKING, the target to be detected is presented to one eye and a mask that reduces the visibility of the target is presented to the other eye.
   a. The rivalrous percept provides the Visual System with Cues to what?
   b. Rivalry would therefore need to take place at stages beyond which what occur?

Answer 21

1. a. to the Relative Distances of the 2 Objects.

b. beyond which Adaptation Occurs.