MOTOR ACTIVATION TIME IN PARKINSONS-DISEASE

Motor activation time (MAT), considered in the present work as the act ual intracerebral processing delay during a reaction time (RT) task, w as assessed in 17 patients with Parkinson's disease (PD) and in 7 age- matched healthy volunteers. MAT was calculated by subtracting from the premotor RT the afferent and efferent times obtained by sensory and m otor evoked potentials. When compared with healthy volunteers, patient s exhibited significantly (p < 0.02) prolonged MATs. In a smaller grou p of 9 PD patients MAT and the auditory P3 event related potential wer e assessed while on antiparkinsonian treatment and after a 12-hour wit hdrawal period. During the off medication condition patients showed a significant slowing (p < 0.01) of MAT values without any remarkable ch ange in P3 latency or amplitude. These results suggest that MAT slowin g indicates an abnormal function of the dopaminergic mechanism involve d in the initiation of movement which is not related to changes in the arousal or cognitive state.