Dissociation between time reproduction of actions and of intervals in patients with Parkinson's disease

Alterations in temporal estimation have been observed in patients with Parkinson's disease (PD) and have been associated to dopaminergic dysfunction. Nevertheless, levodopa treatment and deep brain stimulation of the subthalamic nucleus (DBS-STN) have been shown to improve motor deficits and temporal estimation skills in such patients. So far, temporal estimation tasks in PD patients have evaluated the ability to reproduce intervals of time, but never the duration of an action. Here we investigated: (1) the ability of PD patients to reproduce the duration of their previous actions as compared to their ability to reproduce intervals of time and (2) the effect that DBS-STN has on both skills. Nineteen PD patients with DBS-STN and 19 controls were requested to reproduce the duration of an action and that of an interval of time. The patients were tested in the following treatment conditions: on stimulation/off medication, off stimulation/off medication and off stimulation/on medication. The results demonstrated that patients in the off stimulation/off medication condition under-reproduced the duration of their actions while accurately reproducing the duration of time intervals. The accuracy of the performance improved significantly in both treatment regimens. Our results indicate that in PD patients the ability to reproduce motor acts can be dissociated from that of reproducing time intervals and that it can be improved by the administration of medical or surgical treatment.