Feedback-related potentials and oscillations during trial and error learning in Parkinson's disease

Electrophysiological markers of performance monitoring are thought to reflect functioning of dedicated neural networks and neuromodulatory systems. Whether and how these markers are altered in neurological diseases and whether they can reflect particular cognitive deficits remains to be confirmed. Here we first tested whether the frontal medial feedback-related potential, evoked during a trial and error learning task, is changed in early Parkinsons disease patients compared to control subjects. The potential was not changed in amplitude and discriminated negative and positive feedback as in controls. Feedback-related markers in Parkinsons patients also appeared in time-frequency analyses, unaltered in theta (3-7 Hz) band but reduced in beta (20-30 Hz) oscillations for positive feedback. Beta oscillations power appeared to be dramatically globally reduced during the task. Overall, our results show that Beta oscillation markers of performance monitoring captured by EEG are selectively altered in Parkinsons disease patients, and that they are accompanied by changes in task-related oscillatory dynamics. Significance StatementFrontal neural activity evoked by outcomes reveal the functioning of neural systems devoted to flexible behaviours. Modulations of such activity in Parkinsons disease (PD) patients could reflect specific alterations of neural systems and cognitive processing. The goal is to evaluate whether such activity can serve as markers of the disease. Here, using EEG and a trial and error learning protocol, we show that mid-frontal midline performance feedback-related potentials for different types of feedback were similar in controls and early diagnosed PD patients. However, task-related oscillations revealed alterations in the beta range accompanied by more global beta activity alteration in PD compared to controls subjects. This study provides data relevant to the search for non-motor biomarkers in early stages of PD.