Increased response to visual feedback of drug-induced dyskinetic movementsin advanced Parkinson's disease

To investigate the response to visual feedback of involuntary movements whi ch have a frequency composition similar to cerebellar tremor but are not ca used by cerebellar damage, we have tested six advanced Parkinson's disease (PD) patients with drug-induced dyskinetic movements using visually guided wrist tracking tasks. Tracking performance was assessed under three visual conditions: (1) both guiding target and movement cursor were displayed cont inuously; (2) the target display was turned off for the second half of each trial; or (3) the cursor display, but not the target, was turned off for t he second half of each trial. The response to visual feedback of drug-induc ed dyskinetic movements at 1-5 Hz in these advanced PD patients were signif icantly increased than in normal controls. This suggests that increased res ponse to visual feedback might be a common feature of low frequency involun tary movements and not directly caused by cerebellar damages. (C) 2001 Else vier Science Ireland Ltd. All rights reserved.