Binocular Vision: Lecture 3: Binocular Summation (2)

Question 1

Binocular Summation: Three things

Answer 1

1. Pupillary Diameter
2. Accommodation & Vergence
3. Intraocular Transfer

Question 2

1. What happens when light falls in one eye?

2. Under what conditions is Accommodation Influenced: Monocular or Binocular conditions?

Answer 2

1. It affects the Diameter of the Pupils in BOTH EYES!

2. Both conditions

Question 3

1. Is there any advantage of using 2 Eyes in Suprathreshold Tasks?

Answer 3

1. NO. Once stimuli are easily visible, there’s a LESS ADVANTAGE when viewing w/2 eyes as opposed to one.

Question 4

Reaction Time under Monocular and Binocular Conditions

1. Harwerth used what to measure reaction times of one eye alone and both eyes?
2. When were REACTIONS times SHORTER?
   a. For what?
3. Contrast needed to reach a criterion reaction time is lower under what viewing conditions?

Answer 4

1. They Presented GRATING STIMULI
2. Under Binocular Viewing Conditions
   a. For any Grating Contrast Levels
3. with BINOCULAR VIEWING

Question 5

Binocular Brightness Averaging

1. There are Binocular Interactions to What stimuli?
   a. Some subjects may even show what for Suprathreshold stimuli?
2. The appearance of an object, (like a pencil) will be what the SAME/DIFFERENT under monocular and binocular viewing conditions?

Answer 5

1. to Suprathreshold stimuli, although there’s MORE VARIABILITY in the Degree of Summation than noted for threshold stimuli
   a. Binocular Facilitation
2. will be the SAME!

Question 6

Fechner’s Paradox

1. Under what conditions is it a Paradox?
   a. Why?

Answer 6

1. Binocular Conditions
   a. it’s under binocular conditions where You receive MORE TOTAL LIGHT, and the TARGET looks DIMMER than when viewing w/the unfiltered Eye Alone.

Question 7

Independence Hypothesis

1. What does it state?
   a. So, under this, it would lead one to predict that if the left eye sees the target as dim, and the right eye as bright, what would happen if you closed the left eye?

Answer 7

1. that the 2 Eyes operate Completely Independently
   a. It wouldn’t change the perception cuz the right eye still receives a bright image under binocular vs. monocular conditions

Question 8

Summation Hypothesis

1. What does it predict?
   a. It makes 2 incorrect predictions: What’s the first one?

b. And the Second?

Answer 8

1. Binocular Brightness is the SUM of the 2 Monocular Brightnesses
   a. it predicts that under binocular viewing conditions, the object will BE BRIGHTER than under monocular conditions, WHICH DOES NOT HAPPEN!
   b. it predicts that closing the eye w/a filtered, dimmer image will result in a perceived dimming. THIS is the EXACT OPPOSITE of what happens in FECHNER’s PARADOX!

Question 9

Averaging Hypothesis

1. So The visual system simply does what?
2. If there’s unequal brightness in the 2 eyes, what happens?
3. Binocular Brightness Averaging: What is it?

Answer 9

1. averages the perceived brightness of each eye to arrive at binocular brightness perception
2. the binocular perception would be midway b/w the perceived brightness of each eye alone
3. it’s averaging out the brightness seen by each eye to get a binocular brightness perception (NEURAL SUMMATION)

Question 10

Dominant vs. Non-Dominant Eye

1. Which eye’s brightness and visual direction is weighted more under binocular conditions?
2. Dominate eye will activate a larger portion of what?

Answer 10

1. DOMINANT Eye

2. of the Visual Cortex

Question 11

Inter-ocular Transfer of After-Effects

1. What are After-Effects?
2. Waterfall Illusion: What is it?

Answer 11

1. Visual illusions that come from fatiguing Tuned Visual neurons. (Perception of target viewed afterwards is Biased)
2. View an Adapting Stimulus (unidirectional Motion) long enough to Fatigue Neurons, then view a Stationary stimulus will cause you to Perceive that the object is moving in an Opposite direction

Question 12

Tilt After-Effects

1. When do Tilt Aftereffects transfer more strongly: with Real Tilted Contours, or with Subjective Contours?

Answer 12

1. Subjective Contours

Question 13

Inter-Ocular Transfer of After-Effects

1. What does the Motion aftereffect exhibit?
   a. with the magnitude of the aftereffect being weaker for what?
2. What exhibits more interocular transfer: Random-Dot Displays or Moving Grating Stimuli?

Answer 13

1. Interocular Transfer
   a. for Interocular Transfer than that of the Monocular Aftereffect
2. Random-dot motion displays

Question 14

Visual Masking (1)

1. What is it?
2. When does DICHOPTIC Visual Masking occur?
3. When is Dichoptic Masking Strongest?

Answer 14

1. Degradation of the Perception of a Test Stimulus by 1 SECOND, Masking stimulus presented either before, simultaneously with, or subsequent to the Test Stimulus
2. When this interference is produced from the Mask Stimulus being Presented to one eye and the Test Stimulus to the other eye.
3. When the Mask is Presented to the Dominant Eye

Question 15

Visual Masking (2)

1. How does Simultaneous Masking work?
   a. What does the Mask refer to?
   b. What does the mask interfere with?
2. Simultaneous Masking is More pronounced in what patients?
   a. What effect is this called?

Answer 15

1. The Mask and the Target are present at the SAME TIME
   a. Spatial Gratings
   b. with the Detection of a Stimulus Composed of Similar Frequencies (the Target)
2. Patients with AMBLYOPIA
   a. CROWDING EFFECT

Question 16

Visual Masking (3)

1. What is BACKWARD MASKING?
   a. What does the Mask do?
   b. When can this occur?
2. What happens in Forward Masking?
   a. The mask reduces the visibility of what?
3. Metacontrast: It’s a form of what?
   a. Visibility of a Briefly Presented target is Reduced by the subsequent presentation of what?

Answer 16

1. Target Precedes the Mask
   a. Reduces the Visibility (of the previously presented target)

b. When the Mask is MUCH BRIGHTER than the Target, enabling the Mask’s neural response to reach Central Visual Areas First, thus Interfering w/DETECTION of the Target.

2. The Mask PRECEDES the Target
   a. Of the Subsequently Presented Target
3. of Backward Masking where the mask and target are SPATIALLY ADJACENT
   a. of a Spatially Adjacent Mask

Question 17

Binocular Interactions in Abnormal BV (1)

1. Stereoblind Strabismic Individuals: What is it?
2. When Flicker Thresholds are measured under monocular and binocular conditions in stereoblind subjects, is there a Difference in Sensitivity to In-Phase and Out-of-Phase Flicker?
3. Who have Less impairment of Binocular Summation: Anisometropic Amblyopes or Strabismic Amblyopes?
   a. Why is that?

Answer 17

1. No Binocular Summation beyond that predicted by probability summation is seen.
2. NO!
3. Anisometropic Amblyopes
   a. They Fail to exhibit Binocular Summation and Stereopsis only at high Spatial Frequencies

Question 18

Binocular Interactions in Abnormal BV (2)

1. Is Sub-threshold Summation seen in Stereoblind Strabismic Amblyopes?

Answer 18

1. NO!

Question 19

Binocular Interactions in Abnormal BV (3)

1. Motion Aftereffects show NO Interocular Transfer in what types of Strabismics?
2. Interocular Transfer of Aftereffects is also reduced or Absent in subjects with what strabismus?
3. What Eliminates Excitatory Binocular Interactions (like subthreshold binocular Summation)?
   a. What is preserved though?

Answer 19

1. Early-Onset Strabismics
2. with Early-Onset Strabismus
3. Amblyopia
   a. Inhibitory Binocular Interactions like DICHOPTIC MASKING and INTEROCULAR SUPPRESSION