Binocular Vision: Lecture 13: Suppression and Luster

Question 1

1. What happens when a Localized Contour to one eye and an empty uniform field to the other are combined Binocularly?
2. Where is suppression strongest?

Answer 1

1. The contour Suppresses the uniform field of the other eye.
2. at the Contour Location and Weakens with Spatial Separation from the Contour

Question 2

1. What does the Zone of Suppression result from?

a. The effect is Stronger when the Contour is Placed where in the Retina?

Answer 2

1. from the Inhibitory effect of the Surround Region of Center-Surround Receptive Fields EXCITED by the CONTOUR
   a. at the FOVEA than when it’s placed in the Retinal Periphery

Question 3

1. In the Binocular Percept, the locus where the 2 lines Intersect Seems Darker/Lighter then the other parts of each line.
   a. What does this suggest?
2. What will form just outside of the intersection where the retinal images differ greatly?
3. Binocular Suppression can also happen w/a Focused Sharp contour in one eye and what in the other eye?

Answer 3

1. DARKER
   a. that the Visual System has combined the Info from Each Line at the Location at which the Retinal Images are SIMILAR
2. A Halo of Suppression
3. and a BLURRED CONTOUR of the SAME ORIENTATION in the other EYE!

Question 4

Suppression Vs. Rivalry (1)

1. What happens to Single or small Localized, dissimilar contours?
2. What about Groups of dissimilar contours or large areas of contours?
3. In Suppression, the STRONGER you make the stimulus in one eye, the more it does what?
4. In rivalry, the Stronger you make what in one eye, the Longer it will do what?

Answer 4

1. it’s SUPPRESSED
2. they undergo RIVALRY
3. the More completely it will SUPPRESS the other eye’s image
4. you make the TARGET of one eye, the longer its view will WIN OUT in the Rivalry

Question 5

Suppression Vs. Rivalry (2)

1. What has more influence on the Length of the Suppression Period than the Salience of the Dominant Image?
2. With Rivalrous Stimuli, a Contour w/in the Dominant Image may actually do what?

Answer 5

1. The Strength of the Suppressed Image
2. suppress the neighboring background regions of the other eye’s view, replacing them with the Background of the Dominant Image.

Question 6

Binocular Luster (1)

1. The Locations of the Contours are the same in the images of each eye, BUT the contours are of DIFFERENT what?
2. The Light and Dark Regions of Each Image Are NOT SIMPLY AVERAGED out into what?

Answer 6

1. Luminances

2. a Uniform GRAY

Question 7

Binocular Luster (2)

1. The Background Appears GLOSSY. This is called…?
2. When does Luster occur?
3. The Smaller the Targets, the more likely that what will occur?
4. What will More Frequently Produce Color Rivalry than Luster?

Answer 7

1. BINOCULAR LUSTER
2. when corresponding retinal Points get the SAME Contour info but Different Luminance or Color Information
3. the more likely that COLOR MIXING will occur
4. Large formless displays of differing Color (like looking at a blank while while wearing red/green anaglyphic filters)

Question 8

Binocular Luster (3)

1. The Presence of Rivalry does not prevent what?
2. Rivalry and Fusion with stereopsis are DISTINCT processes mediated by independent Mechanisms. Both mechanisms can be Activated when?

Answer 8

1. the simultaneous Percept of Stereopsis

2. at the same time at the same location

Question 9

Mechanism of Suppression and Rivalry (1)

1. Neurons responding to Stimulation of the Dominant Eye Actively do what?
2. Aftereffects Like Spatial Frequency and Tilt-Aftereffects are Not affected when the Adapted Stimulus is Suppressed in what?

Answer 9

1. Actively inhibit the Activity of Neurons Responding to the Nondominant Eye: Possibly Present in the Laminae of the LGN
2. in a Rivalrous Presentation

Question 10

Mechanism of Suppression and Rivalry (2)

1. Site of Binocular Rivalry Processing might be after the site of processing of what 2 things?
2. As Contrast or Luminance of a Monocular image is Reduced, that image will be seen for how long during Rivalry?
   a. The degree to which its visibility is reduced during its suppressed phase will be INDEPENDENT of its what?

Answer 10

1. Spatial Frequency and Orientation
2. For Shorter Periods of Time during rivalry
   a. of its Contrast or Luminance

Question 11

Mechanism of Suppression and Rivalry (3)

1. A stimulus presented to the Nasal Retina of one eye tends to be what over a stimulus presented to the Temporal retina of the other eye?
   a. Who is more likely to Develop Amblyopia: Esotropes or Exotropes?

Answer 11

1. Nasal = more dominant than temporal

a. ESOTROPES

Question 12

Mechanism of Suppression and Rivalry (4)

1. If Rivalrous stimuli are presented to location in the Peripheral Retina, the size of what INCREASES with Greater Eccentricity from the Fovea?
2. The extend of the Zone is determined by what?

Answer 12

1. the Size of the SPATIAL ZONE of SUPPRESSION increases….
2. by Increasing the Size of a Rivalrous Stimulus until its percept changes from the entire stimulus alternating as a whole to Piecemeal Rivalry in different regions of the stimulus

Question 13

Mechanism of Suppression and Rivalry (5)

1. Suppression requires Spatial Overlap or Close Proximity of the Dominant and Suppressed Images. Suppression is less likely to occur when what?
2. Suppression is less likely to occur when the dominant and suppressed stimuli are what?

Answer 13

1. when the Dominant and Suppressed stimuli are spatially separated, and the duration for which the suppression lasts, decreases.
2. are Spatially separated, and the Duration for which the suppression lasts, decreases.

Question 14

Theories of Rivalry (1)

1. Helmholtz postulated that the Dominant stimulus is Perceived because why?
   a. Rivalry therefore would represent an Alternation of attention to what?
2. Hering: Believed that the Eye with the Greater degree of what will be dominant?

Answer 14

1. because attention is directed to it.
   a. to one, then the other eye.
2. of Contours Present in its image will be dominant

Question 15

Theories of Rivalry (2)

1. The Visual System maintains independent monocular channels for the processing of what info?
2. The Binocular channel is activated ONLY when the images presented to each eye are what?
3. Binocular rivalry is thought to occur at a RELATIVELY HIGH LEVEL IN THE VISUAL SYSTEM because adaptation can occur in Response to a Suppressed Stimulus during Rivalry, even though the suppressed stimulus is not what?

Answer 15

1. Left Eye, Right Eye info, in addition to a purely Binocular Channel
2. are Similar and Fusible
3. Not SEEN

Question 16

Where in the Brain does the Neural Basis of Rivalry Occur?

1. The surface Field potentials measured above the occipital lobe show that under conditions of rivalry, the right and left eye VEPs (visually evoked potentials) Amplitudes are what?
   a. This is evidence that Rivalry occurs where?

Answer 16

1. Are Inversely Correlated (when one increases, the other decreases)
   a. in the Visual Cortex or BEFORE. It’s hard to locate the precise site of rivalry with this approach.

Question 17

1. The Size of the area of suppression is typically proportional to what?
   a. It’s Common for the region of suppression (THE BINOCULAR SUPPRESSION SCOTOMA), to encompass what?
2. These patients will have reduced stereopsis in their Central Visual Fields at the Locus of the Suppression Zone, yet can retain Stereopsis where?

Answer 17

1. To the Size of the Angle of Deviation of the Strabismus
   a. To encompass images formed on BOTH of these Points
2. In their Peripheral Visual Fields Outside of this Zone.

Question 18

1. Monovision: On and in Eye Corrections for Presbyopia
   a. One eye corrected for what and the other what?
   b. Success Occurs when the patient only sees what?
2. Monovision works best with what?

Answer 18

1. a. for Distance and the other one for near.
   b. Only sees the FOCUSED IMAGE (“Blur Suppression”)
2. with Low Add Powers or Early Presbyopes with Residual Accommodation

Question 19

Worth 4 Dot Test

1. Colored filters: Red on Right Eye, Green on Left eye.
   a. What is seen on LE Suppression?
   b. RE Suppression?
2. Normal Fusion?
3. Exo Diviation with Diplopia?
4. Eso Deviation w/Diplopia.
5. Alternates R/G (Bottom Dot) = What?
6. Red Filter: RE View?
7. Green Filter: LE View?

Answer 19

1. a. 2 Vertical Red Dot
   b. 2 Horizontal Green Dots and 1 Green dot on the bottom
2. Top vertical red, 2 horizontal green, and one white dot
3. Red vertical dots to the left
4. Red vertical dots to the right
5. the red/green alternates = FUSION + RIVALRY
6. Eye w/Red Filter CANT see RED or White dote (they’re the same as the background) and sees the “Green” Dots as BLACK (Green light can’t pass thru the red filter)
7. Only the Top dot is BLACK

Question 20

Four Prism Base Out Test

1. Pt is asked to Fixate a Letter on a Nearpoint Snellen Chart.
   a. Prism introduced before EYE In question, Displacing its image TOWARD the BASE of the PRISM
   b. If the Eye makes a Vergence Movement to follow the Displacement of the image, then the CENTRAL VISION of THAT EYE is NOT what?
   c. IF there is no movement, the Image is presumed to have been displaced w/in what?
   d. The Prism is introduced BASE-OUT for detecting suppression in what?

Answer 20

1. b. is NOT SUPPRESSED
   c. w/in a Suppression Zone, and Hence its Displacement Remains undetected by the Patient.
   d. in Small-Angle Esotropia

Question 21

Bagolini Lenses

1. What are they?

Answer 21

1. Lenses with THIN STRIATIONS in them at an ANGLE of 45 degrees for one eye and 135 degrees for the other.

Question 22

Summary

1. Rivalry Takes about how long to develop?
   a. What is seen Initially?
2. Suppression during Rivalry in normals is more likely as what?
3. Suppression in Strabismics is MORE LIKELY when…?
4. Suppression Reduces what 2 things?
5. Rivalry suppression in Normals does not reduce what things?
   a. So this suggests what?
6. Strabismic Suppression Prevents What?
   a. Thus it Probably occurs in what?

Answer 22

1. about 1 second to develop
   a. Initially both stimuli are seen simultaneously
2. as RE and LE stimuli are more dissimilar
3. as RE and LE stimuli are more dissimilar
4. VA and CS
5. does not reduce Contrast Adaptation, Tilt After-Effect, and the Motion After-Effect
   a. That rivalry seems to occur after V1
6. prevents Contrast Adaptation
   a. in V1