Motor learning and Parkinson's disease: refinement of within-limb and between-limb coordination as a result of practice

Even though the basal ganglia have been assigned a role in motor learning, few studies have addressed motor learning capabilities in Parkinson patient s. In the present experiment, improvement of bimanual figure drawing across practice was compared between Parkinson patients and normal age-matched co ntrols. At regular intervals during acquisition, performance was assessed u nder normal vision and blindfolded conditions. At initiation of practice, t he typical signs associated with Parkinson's disease became evident, such a s bradykinesia and hypometria. Moreover, reduced synchronization between th e force-time specifications of both limbs was observed. When vision was wit hdrawn, Parkinson patients showed a larger drift of drawing performance acr oss the workspace, indicative of a decline in proprioception. In spite of t he aforementioned deficits, Parkinson patients made marked improvements in the speed of execution, the consistency of the spatial trajectories, and th e synchronization between the limbs across practice, even though they never reached the performance levels obtained in elderly controls. The findings demonstrate that Parkinson patients do benefit from practice to refine thei r upper limb control and to alleviate their most basic motor deficits. (C) 2000 Elsevier Science B.V. All rights reserved.