Coordinative and limb-specific control of bimanual movements in patients with Parkinson's disease and cerebellar degeneration.

The present study examined the effects of basal ganglia and cerebellar pathology on bimanual coordination using patients with Parkinson's disease (PD) and cerebellar dysfunction (CD). Twenty patients with idiopathic PD (10 untreated early and 10 advanced PD), 10 patients with cerebellar degeneration, and 11 normal subjects were instructed to perform in-phase and anti-phase bimanual coordination movements. The results indicated that while the quality of coordinated bimanual movements in untreated early PD and CD patients was not significantly different from that of normal controls, advanced PD patients exhibited reduced synchronized coordination during the faster anti-phase mode. This suggests that the observed bimanual coordination abnormalities in PD are not an early sign of the pathophysiology of the disease, and cerebellar degeneration may have minimal consequences on synchronized coordination between the limbs. In terms of the parameterization of individual limb movements, CD patients showed a tendency for hypermetric impairments with more irregular movements, while PD patients exhibited relatively slower limb movements and lower amplitudes than normal controls. Overall, the current data provide evidence of the specific functions of different neural structures involved in the pathological process of PD and CD on bimanual coordination.