L-dopa effects on preprogramming and control activity in a skilled motor act in Parkinson's disease

The authors investigated whether preprogramming (Bereitschaftspotential, BP) and control activity (skilled performance positivity, SPP) in a bimanual, sequential skilled performance task (SPT) is sensitive to L-dopa administration in non-demented Parkinson's disease (PD) patients.

Movement related potentials (MRPs) were recorded in 12 non-demented parkinsonian patients before and after acute L-dopa administration, and in 17 control subjects, all of whom were performing SPT for the first time. BP, SPP and correct performances were evaluated both as a grand average and in sequential blocks in order to verify the learning effect.

After L-dopa administration the PD patients scored a significantly higher percentage of correct performances (P<0.05), linked to a decreased BP amplitude (P<0.001) and an increased SPP amplitude (P<0.005), than before therapy. Dynamic evaluation through the block analysis did not show any learning effect in off-therapy patients but showed that L-dopa intake improved learning, linked to a BP amplitude decrease (P<0.005) and a SPP amplitude increase (P<0.05). Furthermore, L-dopa minimized differences in the learning trend between off-therapy PD patients and controls.

Our findings suggest that skilled motor learning is impaired in non-demented untreated PD patients. Dopaminergic drug administration seems to restore the ability of PD patients to use more automatic motor strategies, as demonstrated by the electrophysiological and behavioural pattern, which became more similar to that of normal subjects.