Effects of Subthalamic Deep Brain Stimulation on Emotion Processing in Parkinson's Disease

Background: Processing of emotion plays a critical role in social interaction. People with Parkinson's Disease (PwPD) may experience impaired facial emotion recognition for negative emotions. Previous evidence regarding the effects of deep brain stimulation in the subthalamic nucleus (STN-DBS) is inconclusive. Objective: To investigate the impact of STN-DBS on emotion processing in PwPD controlling for effects of disease progression and DBS-induced changes in cognitive ability. The secondary aim was to explore the effect of post-DBS adjustments of dopamine replacement therapy. Methods: 32 cognitively intact PwPD (16 DBS, 16 non-DBS) and 22 healthy controls performed tasks assessing recognition and discrimination of emotions and an emotional Go/No-Go paradigm, complemented by task versions using non-emotional stimuli. Baseline assessments were conducted two months before DBS surgery and followed up three months postoperatively. Mixed-effects models analysed group-by-time interactions on task performance measured as accuracy and reaction time. Associations of longitudinal changes in non-motor symptoms and medication dosages with task performance were assessed using bootstrapped Pearson's correlations. Results: A significant DBS-associated increase in reaction times was found specifically in the emotional conditions, while there was no evidence for a DBS-effect on the accuracy of emotion recognition or discrimination. Post-DBS dose reduction of dopamine agonists was associated with improvement in emotion recognition. Conclusion: STN-DBS does not lead to a generalized decline in emotional processing when controlling for important confounders. Instead, changes in response speed suggest altered processing dynamics. Adjustments in pharmacological treatment regimens contribute to altered FER after DBS surgery.