Local field potentials and motor performances modulation in response to stimulation and levodopa: a study on Parkinson's disease patients on chronic deep brain stimulation

Introduction: Subthalamic (STN) local field potentials (LFP) in the beta band are considered potential biomarkers for closed-loop deep brain stimulation (DBS) in Parkinson's disease (PD). Studies focusing on chronic STN LFP modulation in response to stimulation and treatment are scant. Deepening knowledge on beta modulation during chronic stimulation could aid the development of solid computational algorithm for adaptive DBS. This study aimed to investigate: 1) the presence of beta peaks in the first 21 patients receiving the Percept PC at our Tertiary Centre; 2) the influence of medications, stimulation, and plasma levodopa levels on beta-peaks magnitude and motor performances. Methods: Twenty-one (19 males, 2 females) consecutive PD patients who underwent bilateral STN-DBS surgery were prospectively recruited. At 6 months after surgery, an extensive and systematic evaluation of raw LFP, motor performances, and plasma levodopa levels was conducted in the following four conditions: OFF-medications/ON-stimulation; OFF-medications/OFF-stimulation; ON-medications/OFF-stimulation; ON-medications/ON-stimulation. Results: Analysis of STN LFP revealed that 76.2 % (16/21) of PD patients showed a beta peak. Beta peaks was identified at an average frequency of 21.0 ± 5.4 Hz, with an amplitude of 1.1 ± 0.8 μV/rtHz. A higher significant reduction of beta STN oscillations was observed following stimulation activation (p < 0.001) compared to levodopa administration. LFP amplitude patterns reflected motor performance trends across the four treatment conditions. Conclusion: This study provides a comprehensive and systematic evaluation of LFP behaviour in response to stimulation and medication, conducted during ongoing stimulation and in the chronic state. These findings enhance understanding of beta oscillatory changes related to therapies and stimulation.