1294 Intraoperative Investigation of Motor Cortex Responses and Motor Outcomes During Cortical Phase-Dependent Stimulation in Parkinson’s Disease

INTRODUCTION: Deep brain stimulation (DBS) for Parkinson's Disease (PD) typically involves high-frequency stimulation to subcortical structures, independent of cortical oscillatory abnormalities. Recent studies identify abnormal phase-amplitude coupling (PAC) between high-frequency gamma and beta oscillations in the PD motor cortex as a potential biomarker for motor symptom severity. Employing PAC as a biomarker in closed-loop neuromodulation could potentially disrupt this coupling, effectively decoupling beta and gamma oscillations to alleviate symptoms without causing adverse side effects. METHODS: Five PD patients undergoing DBS lead placement in the subthalamic nucleus (STN) participated. During surgery, patients performed a motor task involving finger tapping, hand movements, and pronation/supination. Stimulation pulses, triggered by specific phases of beta oscillations recorded via motor cortex electrocorticography, were administered. A markerless tracking system captured hand movements. We analyzed changes in the PAC modulation index, beta power in the motor cortex, and the hand’s position during various phases of the motor task. RESULTS: Synchronizing stimulation with the peak phase of beta oscillations increased beta-gamma coupling during the task's preparatory phase and decreased the hand's instantaneous velocity during the execution phase. Conversely, stimulating during the trough phase reduced coupling during the preparatory phase and increased velocity during execution. CONCLUSIONS: The timing of DBS relative to beta oscillation phases significantly influences motor responses. Phase-dependent stimulation of the motor cortex could rectify abnormal oscillatory activity and diminish motor symptoms in PD, potentially enabling targeted modulation of specific circuits within the motor system.