Emotionally Arousing Visual Stimuli Modulate Oscillatory alpha Activity Recorded from STN Area in PD Patients

Abstract

High frequency stimulation (HFS) of the subthalamic nucleus (STN) has become a widely accepted therapy to treat motor symptoms in PD patients. In some patients however, stimulation may be accompanied by behavioral and cognitive side effects drawing attention to a possible influence of HFS on associative and limbic circuits within the STN area. To further elucidate the involvement of the human STN region in the processing of emotional information we investigated changes in oscillatory activity within the STN area in response to emotionally arousing visual stimuli. Local field potentials (LFP) were recorded through deep brain macroelectrodes (Medtronic, model 3389) from the STN area in 10 PD patients (6 men, 4 women; age 53.2±3.8 years; 19 sides) during a 1 second presentation of emotionally arousing stimuli (selected from the International Affective Picture System). Data were digitally pass-band filtered in the alpha (8–12Hz) range, squared and responses averaged across pleasant, unpleasant and neutral stimuli. Changes in alpha activity were defined as the percentage decrease (event-related desynchronization-ERD) or increase in band power during the test interval (0.5s to 3s post-stimulus) in comparison to the baseline period (2s before stimulus presentation) for each emotional category. A significant decrease in alpha power was found for all stimulus categories starting at about 0.5s after stimulus presentation. During the post-stimulus time period from 1–2s the ERD was significantly larger in trials of pleasant (mean ERD 21.6%±2.8; p<0.001) and unpleasant (mean ERD 15.0%±4.2; p=0.002) stimuli compared to neutral (mean ERD 4.4%±4.2). The modulation of late alpha activity recorded from the STN area in PD may reflect processing of emotional arousal as it followed both pleasant and unpleasant stimuli. These findings suggest that „limbic“ processing occurs in the region of STN and may offer an explanation for why STN-HFS may be complicated by affective disorders in PD patients.