Goal-directed whisking increases phase-locking between vibrissa movement and electrical activity in primary sensory cortex in rat

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National Academy of Sciences

RESUMO

We tested the hypothesis that behavioral context modulates phase-locking between rhythmic motor activity and concomitant electrical activity induced in primary sensory (S1) cortex. We used exploratory whisking by rat as a model system and recorded two measures: (i) the mystacial electromyogram (∇EMG) as a surrogate of vibrissa position, and (ii) the field potential (∇LFP) in S1 cortex as an indicator of electrical activity. The degree to which the ∇EMG and ∇LFP were phase-locked was compared for three categories of rhythmic whisking: (i) searching for an object with the vibrissae for a food reward, (ii) whisking in air for the goal of returning to the home cage, and (iii) whisking with no reward. We observed that the magnitude of phase-locking was nearly tripled for the two rewarded conditions compared to unrewarded whisking. Critically, increased locking was not accompanied by an increase in the amplitude of the cortical ∇LFP for the rewarded tasks. Additional experiments showed that there was no significant relation between the amplitude of a sensory-evoked response in S1 cortex and the magnitude of the locking between the ∇EMG and the ∇LFP during whisking. We conclude that the behavioral context of a whisking task can increase the modulation of S1 cortical activity by motor output without a concomitant increase in the magnitude of activity.

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