LEARNING MANUAL PURSUIT TRACKING SKILLS IN PATIENTS WITH PARKINSONS-DISEASE

Evidence from a number of sources identifies the putamen and its ultim ate cortical projection sites as forming a possible substrate for moto r learning. The present paper describes two experiments which explored motor learning of a pursuit tracking task under first (position) and second (velocity) order control dynamics, in patients with Parkinson's disease on and off (experiment 2 only) their normal dopaminergic medi cation. In neither experiment did the medicated patients show evidence of significant impairment in learning the tasks. in the velocity trac king task, however; the patients off medication showed significantly l ess improvement in performance with practice. The discussion considers a number of possible interpretations of this finding. Contemporary co gnitive theories of motor learning consider behavioural change with pr actice to be the combined action of art automatic procedural system, t ogether with input from a conscious declarative system. Development of declarative knowledge about the task may have changed the nature of t he process involved, from a visually guided task to a more predictive one based upon an internal representation. Evidence from various sourc es suggests that patients with Parkinson's disease have particular pro blems with this mode of control, thus making the task more difficult. It is suggested that motor control deficits have not been adequately c onsidered in previous studies on motor learning, and that the evidence from clinical studies for a role of the putamen/ supplementay motor a rea in motor learning remains equivocal.