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Corey Ziemba, Robbe Goris, Eero Simoncelli, J. Movshon; Uncoupling choice formation and choice-correlated activity in early visual cortex. Journal of Vision 2017;17(10):1271. doi: https://doi.org/10.1167/17.10.1271.
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Responses of individual task-relevant sensory neurons can predict monkeys' trial-by-trial choices in perceptual decision-making tasks. Choice-correlated activity has been interpreted as evidence that the responses of these neurons are causally linked to perceptual judgements. To test this hypothesis, we studied the responses of neurons in V1 and V2 while two macaque monkeys performed two perceptual discrimination tasks. In the first task, monkeys discriminated fine orientation differences between drifting sinusoidal gratings. Both animals exhibited high behavioral sensitivity, and neuronal sensitivity in both V1 and V2 was high. However, only one animal exhibited significant choice-correlated activity. Surprisingly, this correlation was negative: when a neuron fired more vigorously, the animal was less likely to choose the orientation preferred by that neuron. Moreover, choice-correlated activity emerged late in the trial, and earlier in V2 than in V1. In the second task, monkeys discriminated patches of texture synthesized with varying amounts of higher-order correlations. We previously found that in anesthetized macaques, V2 neurons, but not V1 neurons, were sensitive to these higher-order correlations. Both animals performed with high behavioral sensitivity; neuronal sensitivity was low, though higher in V2 than in V1. We found weak choice-correlated activity in both V1 and V2 in both animals, and the correlation was consistently positive. Choice-correlated activity emerged early in the trial in V2, but late in the trial in V1. Our findings reveal substantial variation in choice-correlated activity across subjects performing the same task, as well as across tasks performed by the same subject. Together, these results suggest that choice-correlated activity in sensory neurons is not a reliable signature of their involvement in perceptual judgments.
Meeting abstract presented at VSS 2017
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