title: Response monitoring in de novo patients with Parkinson's disease.
abstract: BACKGROUND
  Parkinson's disease (PD) is accompanied by dysfunctions in a variety of cognitive processes. One of these is error processing, which depends upon phasic decreases of medial prefrontal dopaminergic activity. Until now, there is no study evaluating these processes in newly diagnosed, untreated patients with PD ("de novo PD").
  
  
  RESULTS
  Here we report large changes in performance monitoring processes using event-related potentials (ERPs) in de novo PD-patients. The results suggest that increases in medial frontal dopaminergic activity after an error (Ne) are decreased, relative to age-matched controls. In contrast, neurophysiological processes reflecting general motor response monitoring (Nc) are enhanced in de novo patients.
  
  
  CONCLUSIONS
  It may be hypothesized that the Nc-increase is at costs of dopaminergic activity after an error; on a functional level errors may not always be detected and correct responses sometimes be misinterpreted as errors. This pattern differs from studies examining patients with a longer history of PD and may reflect compensatory processes, frequently occurring in pre-manifest stages of PD. From a clinical point of view the clearly attenuated Ne in the de novo PD patients may prove a useful additional tool for the early diagnosis of basal ganglia dysfunction in PD.
authors.affiliation: Leibniz Research Centre for Working Environment and Human Factors, WHO Collaborating Research Centre Dortmund, Dortmund, Germany. willemssen@ifado.de
authors.forename: Rita
authors.initials: R
authors.lastname: Willemssen
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller
authors.forename: Michael
authors.initials: M
authors.lastname: Schwarz
authors.forename: Michael
authors.initials: M
authors.lastname: Falkenstein
authors.forename: Christian
authors.initials: C
authors.lastname: Beste