Emotion recognition in Parkinson's disease after subthalamic deep brain stimulation: differential effects of microlesion and STN stimulation

Deep brain stimulation of the subthalamic nucleus (STN-DBS) has acquired a relevant role in the treatment of Parkinson's disease (PD). Despite being a safe procedure, it may expose patients to an increased risk to experience cognitive and emotional difficulties. Impairments in emotion recognition, mediated both by facial and prosodic expressions, have been reported in PD patients treated with such procedure. However, it is still unclear whether the STN per se is responsible for such changes or whether others factors like the microlesion produced by the electrode implantation may also play a role. In this study we evaluated facial emotions discrimination and emotions recognition using both facial and prosodic expressions in 12 patients with PD and 13 matched controls. Patients' were tested in four conditions: before surgery, both in on and off medication, and after surgery, respectively few days after STN implantation before turning stimulator on and few months after with stimulation on. We observed that PD patients were impaired in discriminating and recognizing facial emotions, especially disgust, even before DBS implant. Microlesion caused by surgical procedure was found to influence patients' performance on the discrimination task and recognition of sad facial expression while, after a few months of STN stimulation, impaired disgust recognition was again prominent. No impairment in emotional prosody recognition was observed both before and after surgery. Our study confirms that PD patients may experience a deficit in disgust recognition and provides insight into the differential effect of microlesion and stimulation of STN on several tasks assessing emotion recognition.