THE DYNAMICS OF BIMANUAL CIRCLE DRAWING

A bimanual circle drawing task was employed to elucidate the dynamics of intralimb and interlimb coordination. Right-handed subjects were re quired to produce circles with both hands in either a symmetrical (mir ror) mode (i.e. one hand moving clockwise, the other counter-clockwise ) or in an asymmetrical mode (i.e. both hands moving clockwise or coun ter-clockwise). The frequency of movement was scaled by an auditory me tronome from 1.50 Hz to 3.25 Hz in 8 (8-sec) steps. In the asymmetrica l mode, distortions of the movement trajectories, transient departures from the target pattern of coordination, and phase wandering were evi dent as movement frequency was increased. These features suggested los s of stability. Deviations from circular trajectories were most promin ent for movements of the left hand. Transient departures from the requ ired mode of coordination were also largely precipitated by the left h and. The results are discussed with reference to manual asymmetries an d mechanisms of interlimb and intersegmental coordination.