BIMANUAL COORDINATION IN PARKINSONS-DISEASE

The basal ganglia may be involved in bimanual co-ordination. Parkinson 's disease (which impairs basal ganglia output) is clinically reported to cause difficulties in the performance of co-ordinated bimanual mov ements. Nevertheless, any bimanual co-ordination difficulties may be t ask specific, as experimental observations are equivocal. To infer the role of the basal ganglia in co-ordinating the two arms, this study i nvestigated the bimanual co-ordination of patients with Parkinson's di sease. Sixteen Parkinson's disease patients and matched control subjec ts performed a bimanual cranking task, at different speeds (1 and 2 Hz ) and phase relationships. All subjects performed the required bimanua l in-phase movement on a pair of cranks, at fast (2 Hz) and slow (1 Hz ) speeds. However the Parkinson's disease patients were unable to perf orm the asymmetrical anti-phase movement, in which rotation of the cra nks differed by 180 degrees, at either speed; but instead reverted to the in-phase symmetrical movement. For Parkinson's disease patients, p erformance of the in-phase movement was more accurate and stable when an external timing cue was used; however for anti-phase movement, the external cue accentuated the tendency for patients to revert to more s ymmetrical, in-phase movements.