Abstract
INTRODUCTION
Deep Brain Stimulation (DBS) of Globus Pallidus internus (GPi) is an effective therapy to manage Parkinson disease (PD) symptoms. Despite its documented clinical efficacy, the underlying neural oscillatory mechanisms of GPi-DBS is still not well understood. In this study, we evaluate the hypothesis that therapeutic effects of DBS are mediated by changes in the cortical-subcortical coherence.
METHODS
Seven patients with PD underwent GPi-DBS implantation. Simultaneous recordings of GPi local field potentials (LFPs) and ipsilateral motor cortex electrocorticography (ECoG) were obtained intra-operatively both off and on GPi stimulation. Eighteen seconds of data were used for each condition and the mean coherence was calculated over five different frequency bands of Alpha (8-12 Hz), Low Beta (13-20 Hz), High Beta (21-35 Hz), Low Gamma (36-80 Hz), and High Gamma (81-100 Hz).
RESULTS
>We found a statistically significant (p-value corrected <0.02, Friedman test) reduction of pallidocortical coherence in the High Beta frequency band. No statistically significant difference was observed in the other frequency bands between off and on DBS conditions. This decrease was specific to the primary motor cortex, and no statistical cortical-subcortical coherence difference was observed at the premotor and sensorimotor sites between the two conditions.
CONCLUSION
These findings suggest pallidocortical High Beta coupling may be a critical mechanism in the pathophysiology of PD. GPi-DBS might, therefore, exert their therapeutic effect by inhibition of this exaggerated pallidocortical High Beta coupling. A better understanding of the DBS mechanisms on the alleviation of PD symptoms can contribute to the development of closed-loop DBS in which the patients' neurophysiological parameters will be considered in optimizing the DBS parameters.
Direct Activation of Primary Motor Cortex during Subthalamic But Not Pallidal Deep Brain Stimulation
