Evidence for movement preprogramming and on-line control in differentiallyimpaired patients with Parkinson's disease

Investigated were those aspects of motor planning and execution underlying movement dysfunction in patients with Parkinson's disease (PD). Specificall y examined was the effect of disease severity on these processes. An experi ment is reported that dissociates preprogramming processes from on-line pro gramming processes in a simple motor task that varies in movement complexit y. Dependent measures included reaction time, movement time, as well as kin ematic measures of peak velocity, peak acceleration, peak deceleration, and their respective time values, plus inter-trial variability and EMG activat ion. While PD patients as a whole were able to pre-program movements, inter -trial variability for these measures was increased for more severely affec ted PD patients. Nonetheless, evidence for on-line programming occurred for all PD patients in later intervals of more complex movements. Further, EMG impulses correspond with acceleration trace deviations. The data as a whol e support the hypothesis that disrupted basal ganglia function influences t he consistency of cortical activation and the selection of motor program co mponents.