Does gravity influence the timing of motion? A project study on isochronous repetitive movements in human healthy subjects

The ability to perform isochronous repetitive movements while listening to a paced auditory stimulus requires a flexible process that integrates timing information with movement. Our group has developed and studied an audio-motor and recall-motor integration paradigm in which sets of repeated isochronous wrist"s flexion-extensions (IWFEs) are performed under different sensory conditions while minimizing visual and tactile information. Data indicate that the listening alone to paced auditory stimuli does not improve the precision of an isochronous performance (Modulation of isochronous movements in a flexible environment: links between motion and auditory experience. Bravi et al., 2014, Exp Brain Res, DOI 10.1007/s00221-014-3845-9). Recently, using the same paradigm, we tried to get further insights into the domain of repetitive timed movements by introduction of an external perturbation of the motor peripheral (kinesiotaping), thus showing how the precision of isochronous performance is subject to peripheral contribution. In line with our previous studies we are investigating, by means of a synchronization-continuation paradigm under different audio conditions, whether and how the gravity vector influences the production of IWFEs. First, sets of IWFEs are performed with the forearm, supported on armrest, in pronated position. Second, sets of IWFEs are performed with the forearm internally rotated by 90 degrees. Kinematic parameters were evaluated during each session and temporal parameters of movements were analyzed. Preliminary results suggest that the gravity vector influences isochronous movements by altering their durations. Results provide further evidence for an adaptable control of timing in the audio-motor coupling for isochronous movements.