Changes in reaching reaction times due to volitional modulation of beta oscillations

Hypotheses about what drives beta oscillations in local field potentials (LFPs) of motor areas are numerous and include action inhibition, muscle stiffening, sensorimotor processing, and increased attention. Here, a subject performs variations on a reaching task where they experience either predictable or unpredictable `go cue´ times and target locations in blocks. The beta (25-40 Hz) power time course is analyzed as the subject learns the statistics of the hold time and target location. While learning a predictable target location correlates with an earlier onset in the pre-reach rise in beta, learning a predictable hold time does not alter beta dynamics. Further, during unpredictable hold times, fast reaction times that are likely in anticipation of the `go cue´ exhibit reduced beta desynchronization compared to slower reaction times where the subject likely has waited for the `go cue´ prior to movement initiation. These findings point to a role of beta power in inhibition of prepared actions. We test this hypothesis with a combined operant - conditioning and reaching task where subjects volitionally control their motor cortical beta power and immediately afterwards perform a reaching task. We find that when subjects lower their beta power, their reaction times are significantly faster, supporting the idea that beta power inhibits prepared actions.