Timing and history-dependent processing during sensorimotor synchronization.

Temporal processing is important during skilled actions and often underlies a successful performance. In the present study, functional connectivity profiles as determined by EEG coherence were evaluated in a switching paradigm that assessed the effect of movement rate history upon neural processing. To this end, right-handed subjects initiated tapping responses at a specific tempo, followed by a faster/slower tempo before switching back to the initial tempo. Left and right hand responses were performed and the alternative tempo was adopted by the same or opposite effector. The data showed an increased degree of contralateral intrahemispheric connectivity for slow tapping when preceded by fast tapping; an effect that was strongest for the left hand. When the opposite effector became involved in the switching process, intensification of interhemispheric and midline connectivity additionally occurred. No increase in functional coupling was observed for fast tapping when preceded by slow tapping. Overall, the observations illustrate that the dynamics of motor subroutines within a serial arrangement impose history-dependent operations in timing, which accordingly impacts on the effectiveness of neural processing.