Prefrontal cortex and striatal activation by feedback in Parkinson's disease.

Positive feedbacks reinforce goal-directed behavior and evoke pleasure. In Parkinson's disease (PD) the striatal dysfunction impairs motor performance, but also may lead to decreased positive feedback (reward) processing. This study investigates two types of positive feedback processing (monetary feedback and positive informative feedback), both compared to meaningless feedback, in PD patients and elderly healthy controls, using fMRI. In addition, positive informative feedback will be compared to monetary feedback to determine whether positive informative feedback is just as salient as monetary feedback. Healthy controls showed increased activation in the left putamen during the monetary feedback condition compared to both the positive informative and meaningless feedback condition, without an effect in the medial Prefrontal Cortex (mPFC). In contrast, PD patients showed increased activation in the left putamen during the meaningless feedback condition compared to both positive feedback conditions. In addition, PD patients showed increased activation of the mPFC during both positive feedback conditions. This suggests that when confronted with positive feedback, the mPFC compensates for the striatal deficit. In conclusion, striatal activation was seen in healthy controls specifically during the monetary feedback condition. PD patients did not differentiate between both types of positive feedback. If PD patients are provided with positive feedback, the mPFC compensates for the striatal dysfunction. If however, PD patients are provided with meaningless feedback, the mPFC is less stimulated and the striatum becomes prominent. This study thus demonstrates striatal involvement in positive feedback processing and altered positive feedback processing in PD.