Patients with Parkinson's disease with deep brain stimulation in the subthalamic nucleus postoperatively often display higher impulsivity and therefore may experience difficulties in social interactions. Here, we examined social interactions of patients with Parkinson's disease with and without deep brain stimulation in the subthalamic nucleus in competitive situations. We hypothesized altered self-estimation and risk-seeking behaviour in this patient group induced by deep brain stimulation in the subthalamic nucleus. To test the hypothesis, an experimental setting was used in which participants performed a calculation task and chose their preferred compensation. Based on their actual calculation performance, more patients with Parkinson's disease with deep brain stimulation chose a competitive tournament compensation. Assuming rational behaviour, this self-selection pattern reflects increased risk tolerance. Since patients who performed in the lowest quartile chose the tournament option, the data suggest that deep brain stimulation in the subthalamic nucleus results in a loss of the correct reference frame against which patients with Parkinson's disease evaluate their performance. The stimulation-induced combination of overestimation of their own performance, increased risk-taking, and preference for competitive environments despite poor performance is likely to impact considerably on the patients' social and work life.
Keywords: basal ganglia; decision making; social interaction.