Subthalamic nucleus stimulation affects subjective emotional experience in Parkinson's disease patients

A number of studies have reported impaired facial emotion recognition following subthalamic nucleus (STN) stimulation in Parkinson's disease (PD), and have related these changes to a limbic dysfunction induced by STN stimulation. The present study examined the effect of STN stimulation in PD patients on a specific component of emotion, namely the subjective experience of emotion. Thirteen post-operative PD patients, 13 pre-operative PD patients matched on clinical and neuropsychological characteristics, and 16 controls matched on age and education, were administered a validated battery of film excerpts known to primarily induce specific emotional feelings (anger, happiness, sadness, fear, disgust, and neutral), and self-rated the intensity of their emotional feelings on a discrete emotions questionnaire. The post-operative group showed a significant lower level of differentiation between the target feeling (i.e., the more likely to be reported) and non-target feelings for the film excerpts intended to induce “sadness” and “fear” respectively, as compared with the pre-operative and healthy control groups. Moreover, the post-operative group reported significantly less intense feelings of fear, anxiety and disgust for the excerpt intended to induce “fear” as compared with the pre-operative and the control groups, while no significant difference was observed between the pre-operative and control groups. Finally, the post-operative group reported significantly less intense feelings of sadness and anxiety during the excerpt intended to induce “sadness” as compared to the control group, although the differences between the pre- and post-operative groups and between the pre-operative and the control groups did not reach significance. Our study suggests that STN stimulation affects the subjective experience of emotion, thus providing a preliminary account of the modulation induced by STN stimulation of a distributed neuronal network underlying the subjective experience of emotion, although the exact contribution of the STN within such network remains to be specified.