The average Bereitschaftspotential (BP) preceding a rapid, self-paced voluntary extension movement of the index finger was recorded from 6 scalp locations in 14 patients with Parkinson's disease who had been withdrawn from their normal drug therapy for at least 12 h before testing. The amplitude of the potential was measured at the peak negativity (N1) and 650 ms prior to this (NS1), and compared with that recorded in a group of 12 age-matched control subjects. The N1 amplitude was the same as in the normals, but the NS1 component was smaller in the patients, especially in midline leads. As a result, the rise in the BP between the peak NS1 and N1 component (termed NS2) was larger in the patient group. The NS1 component of the BP is thought to reflect preparatory activity in the supplementary motor area (SMA) of cortex. Since the basal ganglia provide a major source of afferent input to SMA, the reduction in NS1 in the patients probably results from inadequate basal ganglia activation of SMA. The larger NS2 component may reflect extra activity in other brain areas to compensate for the reduced SMA activity.

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Prosodic features in the speech production of 21 patients with idiopathic Parkinson's disease were tested. The appreciation of vocal and facial expression was also examined in the same patients. Significant intergroup differences were found in the prosody production tasks but, in contrast to previous results, not in the receptive tasks on the recognition and appreciation of prosody and of facial expression. The discrepancy between the production and recognition of prosodic features does not support the suggestion that dysprosody in Parkinson's disease is necessarily a disorder of' processing emotional information that could be misinterpreted as a dysarthria.