Performance monitoring and error processing during a lexical decision task in patients with Parkinson's disease.

To evaluate performance monitoring and error processing during lexical decision tasks, event-related potentials (ERPs) obtained by time-locked to correct and error responses were studied in 17 Parkinson's disease (PD) patients without dementia and 15 healthy elderly participants. The amplitude of error negativity (Ne) obtained by averages time-locked to error response was significantly reduced in the PD patients, whereas there were no significant differences in the negative component for the correct response (Nc) between the two participant groups. The amplitude of the error positivity (Pe) and correct positivity (Pc) after the Ne and Nc components was also significantly reduced in the PD patients. The PD patients showed significantly slower reaction times and higher error rates. The reduced amplitude of the Ne, Pe, and Pc components in the PD patients suggested impaired performance and conflict monitoring as well as abnormal response strategy adjustments and deviant in later error monitoring processes associated with emotional, conscious evaluation of the error.