Abstract
In rapid limb oscillations, bursts of muscle activity occur during certain phases of the movement. The authors examined phase stabilization in rapid oscillations of the index finger in a horizontal plane. Phase stabilization was rapid; therefore, a deviation from the mean phase was, on average, (almost) completely corrected in the subsequent movement cycle. Participants (N = 11) achieved rapid phase stabilization by using phase-dependent modulations of both the frequency of finger oscillation and the duration of interburst intervals. For example, with an early phase of a burst, oscillation frequency was increased immediately and the next burst of muscle activity was delayed. Whereas phase-stabilizing modulations of oscillation frequency are likely to be mechanically mediated, phase-stabilizing modulations of the timing of bursts of muscle activity must be neurally mediated. The present findings therefore strongly suggest that a central pattern generator does not generate rapid finger oscillations in an open-loop mode, but the pattern-generator network integrates, individually or in combination, afferent signals or predictive signals on the current or future states of the oscillating finger.
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