Binocular Vision: Lecture 2: Binocular Summation (1)

Question 1

1. 4 reasons why we need binocular vision?

Answer 1

1. Increased VA and CS
2. Stereopsis
3. Field of View
4. Spare Eye (?)

Question 2

1. Define Binocular Summation

Answer 2

1. It’s adding Info from EACH EYE to give us a BINOCULAR VISUAL PERFORMANCE that EXCEEDS Monocular Performance

Question 3

1. Does Performance on Visual Tasks like reading, Improve w/Binocular Viewing conditions?
2. What about Luminance Detection, Brightness matching, reaction times, Critical Flicker Frequency (CFF), Visual Acuity, Etc?

Answer 3

1. IDK…Look it up in the book when it comes!

Question 4

1. In what 2 situations do 2 Eyes DOUBLE the PERFORMANCE?
2. When are 2 Eyes not better than one?
3. When are 2 Eyes Slightly Better?
4. When are 2 Eyes WORSE than one eye?

Answer 4

1. Complete Linear Binocular Summation, AND Binocular Facilitation
2. When there is NO BINOCULAR SUMMATION
3. Partial Binocular Summation
4. Binocular Inhibition

Question 5

1. When Ocular Output of Right and Left Eye are both +1.00, what happens when they sum in Visual Cortex Output:
   a. +1.00
   b. +2.00
   c. +2.40
   d. +1.80
   e. +0.40

Answer 5

1. a. No Summation
   b. Complete Summation
   c. Facilitation
   d. Partial Summation
   e. Inhibition

Question 6

Sherington’s Investigation (1)

1. When an Identical Flicker is shown in Each Eye, IN PHASE, BINOCULAR SUMMATION would predict greater sensitivity to the flicker when viewed how?
2. What happens when Flicker is 180 degrees OUT OF PHASE b/w the 2 eyes?
3. What would happen if no Binocular Summation occurred?

Answer 6

1. When viewed Binocularly than when viewed Monocularly
2. the flicker would be CANCELLED out under Binocular conditions if Summation occurred, thus REDUCING SENSITIVITY
3. No difference b/w in-phase and out-of-phase conditions cuz the Amplitude of flicker would be the Same in either eye.

Question 7

Sherington’s Investigation (2)

1. First Evidence supporting the existence of binocular Summation:
   a. If no binocular summation occurred, what would happen?
   b. What would this result in?

Answer 7

1. a. The higher perceived amplitude of Flicker w/Binocular Viewing in the In-phase condition would yield a HIGHER CFF.
   b. The lower perceived amplitude in the out-of-phase condition would yield a LOWER CFF

Question 8

Binocular vs. Monocular Temporal Contrast Sensitivity Function (1)

1. They measured TEMPORAL CONTRAST SENSITIVITY for several temporal frequencies using what wave flicker?
   a. What, in order, had highest to lowest sensitivity: Binocular-in phase, Monocular flicker, and Binocular out-of phase sensitivity?

Answer 8

1. Sine-wave flicker w/gradually increasing and decreasing the brightness levels
   a. Binocular in-phase > Monocular flicker sensitivity > binocular out-of-phase sensitivity

Question 9

Binocular vs. Monocular Temporal Contrast Sensitivity Function (2)

1. What did Sherrington find in regards to the CFF of Binocular in-phase and out-of-phase flicker sensitivities when compared directly?
   a. This is also evident when Binocular (In-phase) Sensitivity is compared to what?
2. When is there LITTLE difference in a person’s RESPONSE to BINOCULAR FLICKER?
   a. Where are Benefits of Binocular Summation seen? (at what frequencies)

b. The Ratio of Binocular to Monocular Thresholds is what at Low frequencies?
c. What about at High Temporal Frequencies?

Answer 9

1. That there was just a SMALL Difference in the CFF!
   a. to Monocular Sensitivity
2. At HIGHER TEMPORAL FREQUENCIES
   a. In the Low to Medium Temporal Frequencies.
   b. 1.4 to 1.6
   c. it drops to only 1.15

Question 10

Degree of Binocular Summation DEPENDS on Temporal Frequency of the Stimulus

1. Low Temporal Frequencies?
2. Middle Temporal Frequencies?
3. High Temporal Frequencies?

Answer 10

1. Facilitation Occurs
2. Complete Summation
3. Partial Summation

Question 11

How is info from the 2 eyes combined for other visual functions?

1. In light detection Experiments, what are the differences in Binocular Absolute Detection Thresholds and Monocular Thresholds?

Answer 11

1. Binocular Absolute Detection Thresholds are only slightly LOWER than Monocular Thresholds

Question 12

Binocular Summation: VA vs. CSF

1. What does Acuity Represent on the Spatial Contrast-Sensitivity Curve?
2. Spatial Contrast Sensitivity Performance is consistently about how many times HIGHER than the monocular performance?

Answer 12

1. Only 1 POINT on the curve

2. It’s consistently about 1.4 times higher than the Monocular Performance regardless of the Spatial Frequency measured

Question 13

Binocular Summation

1. There are three things that are considered in Binocular Summation: What are they?

Answer 13

1. Probability Summation
2. Neural Summation
3. Signal to Noise Ratio

Question 14

Probability Summation (1)

1. What does the independence theory of Binocular summation predict?
2. What produces better performance: using 2 detectors or just 1 detector?
   a. Inputs from the 2 eyes are not what?
   b. A Central Decision-making process has access to what?

Answer 14

1. Just cuz a person has 2 eyes, even if they worked completely INDEPENDENTLY, LOWER THRESHOLDS would be expected under binocular Conditions than w/one eye alone
2. 2 detectors
   a. Are NOT COMBINED. They’re processed independently
   b. to both Monocular Inputs

Question 15

Probability Summation (2)

1. If the neurons in our eyes acted independently and they didn’t converge on a common binocular neuron in the visual cortex, Binocular Performance would be expected to improve by what?
2. What is PROBABILITY SUMMATION?

Answer 15

1. By 40%

2. it’s the DEGREE of improvement one would expect by using 2 Eyes even w/o Binocular Combination of info.

Question 16

Probability Summation (3)

1. Is Probability summation the only reason we see better w/2 eyes?

Answer 16

1. NO. If we stimulate 2 eyes, but present TARGETS to widely separated non-corresponding points, we would not expect Binocular Neural Combination to Occur

Question 17

Binocular Integration Period (1)

1. What happens if we present 2 stimuli, one after the other, w/a long temporal delay b/w them?
2. Probability summation DOES NOT require Spatial or temporal synchrony b/w the 2 exposures of the target in both eyes; IT
   ONLY REQUIRES WHAT?

a. SO, The TRUE TEST for NEURAL BINOCULAR SUMMATION is to stimulate what?

Answer 17

1. it would PREVENT BINOCULAR NEURAL COMBINATION, yet allow probability summation
2. that more than 1 exposure to the stimulus does occur.
   a. stimulate both eyes when fusion is allowed and also when it’s prohibited. If thresholds improve when fusion is allowed, Neural Summation must exist.

Question 18

Binocular Integration Period (2)

1. Matin measured ABSOLUTE light detection thresholds under monocular and binocular conditions while varying the Interstimulus Interval (ISI) b/w the left and right eye presentations b/w 0 and 100 ms.
   a. When BOTH EYES viewed the target at the SAME TIME (ISI = 0), what were Binocular Thresholds like?
2. What did this experiment prove?
   a. Binocular Summation has been shown to occur for what 2 situations?
   b. Would Neural summation occur outside of Panum’s Fusional Area?

Answer 18

1. a. They were 80% LOWER than MONOCULAR THRESHOLDS
2. That NEURAL SUMMATION DOES OCCUR, but ONLY IF you STIMULATE BOTH EYES w/in a Binocular Integration Period of 100 ms.
   a. For Both Light Flashes and Grating Stimuli.
   b. NO. The points won’t converge onto a single binocular cortical neuron

Question 19

1. What Conditions prevent the Synchronous presentation of the Stimuli to Both Eyes?
2. Stimuli presented to each eye also have to be what?

Answer 19

1. Amblyopia, Anisometropia, and Strabismus

2. Similar

Question 20

Signal to Noise Ratio

1. Using 2 Detectors, the improvement using 2 eyes would be a factor of what?
2. Internal Neural Noise will also be added from what?
3. If the noise is random, then what might happen?
4. The Visual Performance improvement by a factor of 1.41, can be explained by what?

Answer 20

1. of the square root of 2, = 1.41
2. together from the 2 eyes
3. they might cancel each other
4. by Neural Combination of the activity from the 2 eyes, rather than probability summation alone

Question 21

Binocular Summation

1. Depends on what 3 factors?

Answer 21

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

Question 22

Binocular Summation

1. Also depends on what 3 things?

Answer 22

1. Probability Summation
2. Signal to Noise Ratio
3. Neural Summation