Dependence of reaction times on movement patterns in patients with Parkinson's disease and those with cerebellar degeneration.

Premotor times (PMTs) of both biceps muscles in flexion and supination of the forearms were examined in 13 patients with Parkinson's disease (PD), 10 with cerebellar degeneration (CD) and 14 control subjects. Compared with the control, PMT of CD increased definitely but that of PD was within normal range. The difference of PMTs between flexion and supination was lost in PD, but not in CD. It is assumed that the basal ganglia and the right cerebral cortex are functioning for the selection of movement patterns at the initiation of movements.