Subthalamic oscillatory activities at beta or higher frequency do not change after high-frequency DBS in Parkinson's disease

This study aimed to assess whether changes in the patterns of local field potential (LFP) oscillations of the subthalamic nucleus (STN) underlie to the clinical improvement within 60 s after turning off subthalamic DBS. We studied by spectral analysis the STN LFPs recorded in 13 nuclei from 7 patients with Parkinson's disease before and immediately after unilateral high-frequency (130 Hz) stimulation of the same nucleus, when the clinical benefit of DBS was unchanged. The results were compared with LFP data previously reported [A. Priori, G. Foffani, A. Pesenti, F. Tamma, A.M. Bianchi, M. Pellegrini et al., Rhythm-specific pharmacological modulation of subthalamic activity in Parkinson's disease. Exp. Neurol. 189 (2004) 369–379] – namely 13 STN from 9 parkinsonian patients recorded before and after levodopa administration – which were used as a control. Before DBS, in the ‘off’ clinical state after overnight withdrawal of dopaminergic therapy, the STN spectrum did not significantly differ from the control nuclei, showing prominent activity at beta frequencies (13–20 and 20–35 Hz). After DBS (10–15 min) of the STN, the recorded nuclei significantly differed from the control, failing to show significant changes either in the beta bands or at higher frequencies (60–90 and 250–350 Hz). The patterns of subthalamic LFP oscillations after DBS therefore differ from those after dopaminergic medication. These results suggest (1) that subthalamic LFP modulations are not the epiphenomenon of peripheral motor improvement and (2) that the transitory clinical efficacy maintained after discontinuation of subthalamic DBS is not associated with local modulation of LFP activity at beta or higher frequencies within the STN.