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Christopher Said, Ryan Egan, Marlene Behrmann, David Heeger; Normal binocular rivalry in autism. Journal of Vision 2012;12(9):1365. doi: 10.1167/12.9.1365.
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© ARVO (1962-2015); The Authors (2016-present)
Evidence from animal models suggests that autism may be caused by an increased excitation/inhibition ratio in cortex (the E/I hypothesis). To test this hypothesis in humans, we measured behavior during binocular rivalry, a well-characterized visual phenomenon that depends critically on the balance between excitation and inhibition. In Experiment 1, we measured the duration of mixed percepts during observation of rival gratings in a sample of autistic adults and matched controls. Based on a computational model, the E/I hypothesis predicts longer mixed percept duration for the autistic population compared to the control population. Observers were shown sustained orthogonal gratings (-45/45 degrees) to the two eyes, and continuously reported whether they were perceiving the -45 degree grating, the 45 degree grating, or a mixture of the two. We found no evidence for a difference in mixed percept durations between the autistic and control populations. In Experiment 2, we investigated traveling wave speed. Traveling waves are a perceptual phenomenon in which the dominance of one percept emerges locally and then expands to overtake the other percept. The E/I hypothesis predicts faster traveling wave speeds in the autistic compared to the control population. Observers were shown a ring with high-contrast spiral bands in one eye, and another ring with low-contrast radial bands in the other eye. Using a brief contrast increment at the top of the radial ring, we induced a traveling wave of the radial pattern, and measured the speed by asking subjects to report the wave onset time at various locations. There was no evidence for a difference in the wave speed between the two populations. While our results do not falsify the E/I hypothesis, they suggest that an obvious E/I imbalance is not present in the visual cortex of autistic individuals.
Meeting abstract presented at VSS 2012
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