1. Space Perception and Binocular Vision6
Space Perception and Binocular Vision

2. Binocular Vision and Stereopsis
How is stereopsis implemented in the human brain?
Fundamental requirement: Input from two eyes must converge onto the same cell
Many binocular neurons respond best when the retinal images are on corresponding points in the two retinas: Neural basis for the horopter
However, many other binocular neurons respond best when similar images occupy slightly different positions on the retinas of the two eyes (tuned to particular binocular disparity)

3. Figure Simplified diagrams of receptive fields for two binocular disparity–tuned neurons in striate cortex
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4. Combining Depth Cues
Bayesian approach: A statistical model based on Reverend Thomas Bayes’ insight that prior knowledge could influence our estimates of the probability of a current event
Bayesian approach is the formal model of UNCONSCIOUS INFERENCE

5. Figure Three of the infinite number of scenes that could generate the retinal image in Fig. 6.37
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6. Combining Depth Cues
Ideal observer: A theoretical observer with complete access to the best available information and the ability to combine different sources of information in the optimal manner
It can be useful to compare human performance to that of an ideal observer
Illusions and the construction of space
Our visual systems take into account depth cues when interpreting the size of objects

7. Figure 6.40 The two figures lying across these train tracks are the same size in the image
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8. Figure 6.41 All of the red lines in this illustration are the same length
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9. General context, not distance cues influencing perception
Figure The vertical lines are parallel in (a), as are the horizontal lines in (b)
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General context, not distance cues influencing perception

10. Combining Depth Cues
Binocular rivalry: The competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes

11. Figure 6.44 Two stimuli battling for dominance
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12. Development of Binocular Vision and Stereopsis
How to measure binocular vision?
Stereoacuity: A measure of the smallest binocular disparity that can generate a sensation of depth
Dichoptic: Referring to the presentation of two stimuli, one to each eye. Different from binocular presentation, which could involve both eyes looking at a single stimulus
Stereoacuity is often tested using dichoptic stimuli

13. Figure 6.45 The onset of stereopsis
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14. Figure 6.46 The development of stereoacuity
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15. Development of Binocular Vision and Stereopsis
Abnormal visual experience can disrupt binocular vision:
Critical period: In the study of development, a period of time when the organism is particularly susceptible to developmental change
Strabismus: A misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye, and on the nonfoveal area of the other (turned) eye
Suppression: In vision, the inhibition of an unwanted image

16. Figure Left esotropia
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17. Development of Binocular Vision and Stereopsis
Esotropia: Strabismus in which one eye deviates inward (cross-eyed)
Exotropia: Strabismus in which one eye deviates outward
Next time: perceiving movement