Spatiotemporal relations and movement trajectories in visuomotor synchronization

This work investigates how spatial and temporal aspects of rhythmic movements are affected by spatial and temporal components of a visual pacing sequence. Participants synchronized finger taps with three visual pacing sequences (Flash, High Finger, and Low Finger) at two tempi (500 ms and 400 ms interonset interval). The Flash sequence contained only temporal information, whereas the two Finger sequences contained apparent motion of different amplitudes. Participants' finger movements were recorded with a motion capture system, and movement trajectories and timing accuracy were analyzed. Results indicated that apparent motion facilitates visuomotor synchronization accuracy, which likely stems from tight perception-action links. Stimulus amplitude modulated tap amplitudes in the same direction, but this spatial assimilation did not adversely affect timing accuracy. Flexion times toward the target were significantly shorter than extension or dwell times, and could indicate a relatively ballistic movement trajectory. Local deviations of tap timing correlated with the movement trajectories from the preceding and following movement cycle. For example, after a late tap, the following movement cycle had lower amplitude and shorter extension and dwell times. This could signify the workings of error correction mechanisms that ensure stable synchronization.