Evidence for movement preprogramming and on line control in differentially impaired patients with Parkinson's disease.

Investigated were those aspects of motor planning and execution underlying movem ent dysfunction in patients with Parkinson's disease (PD). Specifically examined was the effect of disease severity on these processes. An experiment is reported that dissociates preprogramm ing processes from on-line programming processes in a simple motor task that varies in movement complexity. Dependent m easures included reaction time, movement time, as well as kinematic measures of peak velocity, peak acceleration, peak deceleration, and their respective time values, plus inter-trial variability and EMG activation. While PD patients as a whole were able to pre-program movem ents, inter-trial variability for these measures was increased for more severely affected PD patients. Nonetheless, evidence for on-line programm ing occurred for all PD patients in later intervals of more complex movements. Further, EMG impulses correspond with acceleration trace deviations. The data as a whole support the hypothesis that disrupted basal ganglia function influences the consistency of cortical activation and the selection of motor program com ponents.