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Lai Ngor Fu, Ronald G. Boothe; A Psychophysical Measurement and Analysis of Motion Perception in Normal and Binocularly Deprived Monkeys. Invest. Ophthalmol. Vis. Sci. 2001;42(11):2547-2553.
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purpose. To measure psychophysically the thresholds for motion detection in the
nasal and temporal directions under monocular viewing conditions in
monkeys reared under conditions of daily alternating monocular
occlusion (AMO). The hypothesis was that motion perception would be
asymmetric with more sensitivity for motion in the nasal direction.
methods. Three monkeys subjected to AMO (AMO monkeys) and three normal monkeys
were studied. All were trained with operant conditioning techniques to
discriminate coherent from random motion in a random dot display. The
percentage of dots in the display that moved either left or right was
varied. Thresholds for motion detection of nasally directed and
temporally directed stimuli were measured to determine whether the
motion perception of AMO monkeys was asymmetric, as predicted.
results. A two-factor analysis of variance revealed a statistically significant
difference between treatment groups (normal versus AMO) and directions
(nasal versus temporal) and a significant interaction. The interaction
was due to a significant difference between nasal and temporal
directions for the AMO group, but no significant difference for the
normal group. Planned comparisons were performed based on each
animal’s best eye (eye most sensitive to nasal motion) and worst eye
(eye least sensitive to temporal motion). No significant differences
were found between the two groups in the best eyes’ responses to the
nasal direction, but the worst eyes’ responses in the temporal
direction were significantly poorer in the AMO group. A neural model
that can account for these findings is based on a Hebbian teacher
located in the nucleus of the optic tract that strengthens connections
of a subpopulation of directionally selective cortical neurons.
conclusions. AMO rearing results in asymmetric motion perception. Thresholds for
detecting nasally directed motion are normal, whereas thresholds for
detecting temporally directed motion are deficient. These results
demonstrate that motion-processing mechanisms in primates exhibit
experience-dependent developmental neural plasticity. The locus of the
neural plasticity could be a subpopulation of directionally selective
neurons in the striate cortex (V1).
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