The effect of a precue on improving movement initiation (i.e., reaction time; RT) is well understood, whereas its influence on movement execution (i.e., movement time; MT) has rarely been examined. The current study investigated the influence of a directional precue (i.e., left vs. right) on the RT and MT of simple and discrete bi-directional movements in a large sample of Parkinson's disease patients and healthy control participants. Both patients and controls were tested twice, with testing sessions separated by 2 hours. Patients were tested first following an overnight levodopa withdrawal and again after they had taken their medication. Both patients and controls demonstrated a significant RT improvement when information was provided in advance. MT in both healthy participants and medicated patients was, however, slower with the provision of advance information, while unmedicated patients showed no significant MT effects. These results suggest that while the basal ganglia may not be involved in motor program selection, they may dynamically modulate movement execution.
A.M. Johnson is with the Faculty of Health Sciences at the University of Western Ontario, London, ON, Canada N6A 3K7. P.A. Vernon is with the Department of Psychology at the University of Western Ontario, London, ON, Canada N6A 5B8. Q.J. Almeida is with the Department of Kinesiology at the University of Waterloo, Waterloo, ON, Canada N2L 3G1. Almeida, L.L. Grantier, and M.S. Jog are with the Department of Clinical and Neurological Sciences London Health Sciences Centre at the University of Western Ontario, London, ON, Canada N6A 5B8.