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Mehrdad Jazayeri, Anthony J. Movshon; Integration of sensory responses in coarse and fine motion discriminations. Journal of Vision 2007;7(9):775. doi: 10.1167/7.9.775.
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© ARVO (1962-2015); The Authors (2016-present)
To make perceptual judgments, the brain must decode the responses of sensory cortical neurons. The direction of visual motion is represented by the activity of direction selective neurons. These neurons are often broadly tuned and inherently noisy, so to infer the direction of motion reliably the brain must appropriately integrate their responses. The optimal integration strategy is task-dependent. For coarse direction discriminations, neurons tuned to the directions of interest provide the most reliable information, but for fine discriminations, neurons with preferred directions off to the sides of the target directions are more reliable. To examine how the visual system pools the activity of direction selective neurons, unbeknownst to observers engaged in a coarse of a fine direction discrimination of random-dot stimuli, we added subthreshold motion signals of different directions to the stimulus to perturb the responses of different groups of direction selective neurons. The pattern of biases induced by subthreshold signals of different directions indicate that (1) subjects' choice behavior relies on the activity of neurons with a wide range of preferred directions and, (2) for coarse discriminations, observers' judgments are most strongly determined by neurons tuned to the target directions, but for fine discriminations, neurons with preferred directions off of the stimulus direction have the largest influence. Our results therefore show that perceptual decisions rely on a population decoding strategy that takes the statistical reliability of sensory responses into account.
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