TEMPORAL PROCESSING IN THE BASAL GANGLIA

This study investigated the role of the basal ganglia in timing operat ions. Nondemented, medicated Parkinson's disease (PD) patients and con trols were tested on 2 motor-timing tasks (paced finger tapping at a 3 00- or 600-ms target interval), 2 time perception tasks (duration perc eption wherein the interval between the standard tone pair was 300 or 600 ms); and 2 tasks that controlled for the auditory processing (freq uency perception) demands of the time perception task and the movement rate (rapid tapping) in the motor-timing task. Using A.M. Wing and A. B. Kristofferson's (1973) model, the total variability in motor timing was partitioned into a clock component, which reflects central timeke eping operations, and a motor delay component, which estimates random variability due to response implementation processes. The PD group was impaired at both target intervals of the time perception and motor-ti ming tasks. Impaired motor timing was due to elevated clock but not mo tor delay variability. The findings implicate the basal ganglia and it s thalamocortical connections in timing operations.