The error negativity in nonmedicated and medicated patients with Parkinson's disease

Objective: It has been hypothesized that the error negativity (Ne or ERN) is modulated by the midbrain dopaminergic system. Thus, in a depleted dopaminergic system as seen in patients with Parkinson's disease (PD) one would expect an attenuated Ne. However, studies investigating the error negativities in medicated patients with PD have produced contradictory results and the present study was designed to explore this relationship further. Methods: Using the event-related potential technique and an Eriksen flanker paradigm, we examined error negativities in nonmedicated (drug naive) and medicated PD patients and compared them to those of healthy controls. Results: (a) The error negativities of the nonmedicated and medicated PD patients were attenuated compared to those of healthy elderly controls at frontocentral scalp sites; and (b) nonmedicated and medicated PD patients produced error negativities similar to each other. Conclusions: PD results in diminished error negativities both in the early stage nonmedicated patients and in the later stage medicated patients. Significance: Because both patient groups have reduced dopaminergic functioning compared to healthy controls, these findings are consistent with Ne amplitude being sensitive to modulations in that system. (C) 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.