Impaired proactive cognitive control in Parkinson’s disease

Abstract

Adaptive control has been studied in Parkinson’s disease (PD) mainly in the context of proactive control and with mixed results. We compared reactive- and proactive control in 30 participants with Parkinson’s disease (PD) to 30 age matched healthy control participants (HC). The electroencephalographic (EEG) activity of the participants was recorded over 128 channels while they performed a numerical Stroop task, in which we controlled for confounding stimulus-response learning. We assessed effects of reactive- and proactive control on reaction time-, accuracy- and EEG time-frequency data. Behavioral results show distinct impairments of proactive- and reactive control in participants with PD, when tested on their usual medication. Compared to healthy control (HC) participants, participants with PD were impaired in their ability to adapt cognitive control proactively and were less effective to resolve conflict using reactive control. Successful reactive and proactive control in the HC group was accompanied by a reduced conflict effect between congruent and incongruent items in midline-frontal theta power. Our findings provide evidence for a general impairment of proactive control in PD and highlight the importance of controlling for the effects of S-R learning when studying adaptive control. Evidence concerning reactive control was inconclusive, but we found that participants with PD were less effective than HC participants in resolving conflict during the reactive control task.