HAND COORDINATION IN BIMANUAL CIRCLE DRAWING

Two right-handed and 2 left-handed participants drew circles in the horizontal plane with both hands simultaneously in either a symmetrical or an asymmetrical mode, at their preferred rate or as fast as possible. During symmetrical movements, the hands showed frequency and phase synchronization at both rates. During fast asymmetrical movements, the hands showed increased phase difference and phase variability, as well as transitions to symmetrical movements, and cases of frequency decoupling. Large distortions of the hand trajectory were also observed under fast asymmetrical movements. Trajectory distortions and movement direction reversals were confined to the nondominant hand. Under the assumption that circular trajectories are generated by properly timed orthogonal oscillations along the y-axis and the x-axis, these findings are accounted for by the characteristics of coupling between homologous functional oscillators of the 2 body sides.