Modulation of subthalamic nucleus local field potential power during incremental isometric force generation in Parkinson's disease patients

Local field potential (LFP) investigations of the subthalamic nucleus (STN) of patients with Parkinson’s disease have provided evidence for pathologically exaggerated oscillatory beta-band-activity (12–30 Hz) which is amenable to physiological modulation by, e.g., voluntary movement1. Previous fMRI studies in healthy controls have provided evidence for an increase of STN blood-oxygenation-level-dependent (BOLD) signal in incremental force generation tasks2. However, how neuronal activity encodes force generation and the topography of its neural correlates within the human STN remain to be elucidated. We hypothesised that incremental force generation is encoded in the sensorimotor part of the STN by modulation of beta-band activity. STN-LFPs were recorded intraoperatively in 13 patients with Parkinson’s disease (37 recording sites) during rest and five incremental force generation conditions of the arm with applied loads of 0g to 400g (in 100g increments). LFP power group data analyses by repeated measures ANOVAs revealed a significant modulation in the high beta- (24 to 30 Hz; p=0.024) and gamma-band (70 to 76 Hz; p=0.036) after Bonferroni α-correction. Supporting regression analyses revealed sites with both negative (low force – high beta-band power, high force – low beta-band power) and positive modulation. The former was found throughout dorsal, lateral and caudal STN regions, whereas the latter was localised in a caudal STN region. Our findings indicate that the modulation of STN-LFP beta- and gamma-band power is involved in encoding physiological force generation in patients with Parkinson’s Disease and that this modulation occurs in STN regions commonly attributed with sensorimotor functions3.