COUPLED TEMPORAL MEMORIES IN PARKINSONS-DISEASE - A DOPAMINE-RELATED DYSFUNCTION

Dysfunction of the basal ganglia and the brain nuclei interconnected w ith them leads to disturbances of movement and cognition, including di sordered timing of movement and perceptual timing deficits. Patients w ith Parkinson's disease (PD) were studied in temporal reproduction tas ks. We examined PD patients when brain dopamine (DA) transmission was impaired (OFF state) and when DA transmission was reestablished, at th e time of maximal clinical benefit following administration of levodop a + apomorphine (ON state). Patients reproduced target times of 8 and 21 sec trained in blocked trials with the peak interval procedure, whi ch were veridical in the ON state, comparable to normative performance by healthy young and aged controls (Experiment 1). In the OFF state, temporal reproduction was impaired in both accuracy and precision (var iance). The 8-sec signal was reproduced as longer and the 21-sec signa l was reproduced as shorter than they actually were (Experiment 1). Th is ''migration'' effect was dependent upon training of two different d urations. When PD patients were trained on 21 sec only (Experiment 2), they showed a reproduction error in the long direction, opposite to t he error produced under the dual training condition of Experiment 1. T he results are discussed as a mutual attraction between temporal proce ssing systems, in memory and clock stages, when dopaminergic regulatio n in the striatum is dysfunctional.