The time course of phase correction : a kinematic investigation of motor adjustment to timing perturbations during sensorimotor synchronization

Synchronizing movements with a beat requires rapid compensation for timing errors. The phase correction response (PCR) has been studied extensively in finger tapping by shifting a metronome onset and measuring the adjustment of the following tap time. How the response unfolds during the subsequent tap cycle remains unknown. Using motion capture, we examined finger kinematics during the PCR. Participants tapped with a metronome containing phase perturbations. They tapped in "legato" and "staccato" style at various tempi, which altered the timing of the constituent movement stages (dwell at the surface, extension, and flexion). After a phase perturbation, tapping kinematics changed compared with baseline, and the PCR was distributed differently across movement stages. In staccato tapping, the PCR trajectory changed primarily during finger extension across tempi. In legato tapping, at fast tempi the PCR occurred primarily during extension, whereas at slow tempi most phase correction was already completed during dwell. Across conditions, timing adjustments occurred primarily 100-250 ms into the following tap cycle. The change in movement around 100 ms represents the time to integrate information into an already planned movement and the rapidity suggests a subcortical route.