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William Curran, Christopher Benton; Direction repulsion facilitates motion segregation. Journal of Vision 2009;9(8):654. doi: 10.1167/9.8.654.
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© ARVO (1962-2015); The Authors (2016-present)
Inhibitory connections exist between motion-sensitive neural units tuned to different directions. Such inhibitory interactions are evidenced in a well known visual illusion, direction repulsion, in which the perceived direction difference between two superimposed transparent surfaces is exaggerated. A possible functional consequence of direction repulsion is to aid the segregation of global motions. If it does facilitate motion segregation then one would expect direction repulsion to be evident at the shortest duration for which two global motions can be perceptually segregated. Two experiments investigated this question. In the first experiment observers were presented with pairs of sequentially presented stimuli - one containing two transparent motion patterns, and one containing three motion patterns. The observers‘ task was to judge which stimulus contained two transparent motions. In the second experiment observers were presented with stimuli containing two transparent motions, and had to make direction judgments of one of the motion components; thus providing a direction repulsion measure. Our results reveal that direction repulsion occurs at the shortest duration at which transparent motions are perceived (circa 100ms). Furthermore, direction repulsion magnitude remains constant across all stimulus durations; thus demonstrating that the underlying inhibitory activity peaks before the perceptual segregation of transparent motions. This is consistent with the view that neural inhibition facilitates motion segregation.
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