EVIDENCE OF INCOMPLETE MOTOR PROGRAMMING IN PARKINSONS-DISEASE

One of the essential questions regarding movement deficits in Parkinso n's disease (PD) is whether they stem from impaired selecting and swit ching among movements, impaired use of predictive information to prepa re movement, or impaired execution of movement. PD subjects (n = 9) an d age-matched control subjects (n = 8) performed a cued, sequential-re sponse RT task. The cue provided either no information, accurate infor mation, or inaccurate information about the upcoming response. PD subj ects used predictive information to prepare and to switch among moveme nt sequences normally, but second and third key press latencies were p rolonged in comparison with the first key press latency. In Experiment s 2 and 3, the effects of choice set and sequence length on key press latencies were examined. These results provide evidence that PD subjec ts initiate movement before the entire response sequence is prepared. PD does not impair motor programming or execution processes themselves but impairs the smooth coordination of those processes.