| Summary: | Simple perceptual decisions are ideally suited for studying the sensorimotor transformations underlying flexible behavior 1 and 2. During perceptual detection, a noisy sensory signal is converted into a behavioral report of the presence or absence of a perceptual experience [3]. Here, we used magnetoencephalography (MEG) to link the dynamics of neural population activity in human motor cortex to perceptual choices in a “yes/no” visual motion detection task. We found that (1) motor response-selective MEG activity in the “gamma” (64–100 Hz) and “beta” (12–36 Hz) frequency ranges predicted subjects' choices several seconds before their overt manual response; (2) this choice-predictive activity built up gradually during stimulus viewing toward both “yes” and “no” choices; and (3) the choice-predictive activity in motor cortex reflected the temporal integral of gamma-band activity in motion-sensitive area MT during stimulus viewing. Because gamma-band activity in MT reflects visual motion strength [4], these findings suggest that, during motion detection, motor plans for both “yes” and “no” choices result from continuously accumulating sensory evidence. We conclude that frequency-specific neural population activity at the cortical output stage of sensorimotor pathways provides a window into the mechanisms underlying perceptual decisions.
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