Precise sensory-motor synchronization is crucial to interact with a dynamic environment, such as dancing with music, playing football, and so on. In order to kick a ball, for example, accurate perception of spatio-temporal information of a ball and correct action are required. The coordination of perception and action has mainly been investigated using synchronized tapping with an isochronous stimulus sequence and psychological studies have shown better tapping performance when synchronizing with moving dot stimuli (continuous condition), compared to static flash stimuli (discrete condition) in the visual domain. This is natural because sensory-motor synchronization in our daily environment is most of the times continuous. However, no study contrasted continuous and discrete auditory stimuli, so it is unclear whether the motion effect depends on the modality or not.
In the present study, we investigated an influence of the motion information of the stimuli on synchronized tapping. Participants were asked to perform a finger-tapping task with an isochronous auditory or visual stimulus sequence with and without motion information (continuous condition vs. discrete condition). In the visual domain, moving dot stimuli improved the accuracy of synchronized tapping, compared to the repetitive presentation of the dot. In the auditory domain, however, moving sounds declined the tapping accuracy, compared to simple repetition of the sound. These results can be interpreted with the difference of the spatial resolution between visual and auditory systems.
As a next step, we are currently conducting the intervention study using transcranial direct current stimulation (tDCS) during the synchronized tapping task with discrete/continuous auditory stimuli. Since the right inferior parietal lobe (rIPL) has an important role in the auditory spatial processing, we hypothesized that the tDCS application to the rIPL would externally modulate synchronized tapping with continuous but not discrete auditory stimuli. The preliminary results of this experiment are also discussed.