Isochronous sounds for isochronous movements: The multiplex control of timing in human subjects.

The ability to perform isochronous movements when listening to rhythmic auditory input requires a foremost and flexible process to manage timing information. We tested whether isochronic movement is result of a multifaceted control process of timing whose individual elements are sensitive or variously resistant to auditory input. We recorded kinematic parameters of movement while participants, free from visual and touch information, performed repeated isochronous wrist's flexion-extensions in silence, driven by streams of beats or excerpts of music, and during auditory recall. Our study on the temporal behavior of isochronous wrist movements reveals composite interrelations between auditory input and motor performance. Some elements of timing are insensitive to auditory information. Other elements of timing are sensitive to auditory input, but only as regarding rhythmic information. Interestingly, the nature of the auditory input is not real-time influential, comes into play only during recall, and for a comprehensive characteristic of rhythmic motor performance: the tempo. Our results provide evidence of a multiplex control of timing in audio-motor coupling for isochronous movements. This intricate framework to control movement offers unique opportunities for the functional exploration of then normal and diseased human brain.