Objective: Identifying physiomarkers of PD motor function beyond total beta power by examining event-related subthalamic nucleus beta modulation during continuous finger tapping (FT) using synchronized local field potentials (LFPs), video-based kinematics, and clinician scores.

Background: Low-beta activity (13–20 Hz) modulates during voluntary movement, and its total power is used as a marker of motor function in Parkinson’s disease (PD). Movement-related beta modulation may be a marker, as it is attenuated in PD [1]. However, beta modulation also reduces with increased movement speed in healthy individuals [2], complicating the interpretation of beta dynamics during continuous motor tasks.

Method: LFP and video data were obtained during 150 assessments in 45 patients performing FT (MDS-UPDRS-III, item 3.4). LFP–kinematic alignment was achieved using artefacts induced by tapping the  IPG [3]. Data was segmented into −0.3 to +0.3 s windows around FT events. Low beta was quantified with the Hilbert envelope and expressed as percentage from a 30 s resting baseline. The latency between event-related desynchronization (ERD) and synchronization (ERS) peaks, as well as the ERD–ERS amplitude difference, were calculated. The differences in these variables between the different severity scores were assessed with a Kruskal–Wallis test.

Results: Synchronization was achieved in 76 assessments (51%). 77 hemispheres were included due to e.g. unilateral recordings, and unidentifiable tapping. ERD-ERS did not differ across MDS-UPDRS-III score groups in amplitude (% change; p = 0.55; median [IQR]: score 0, 16.57 [11.92–23.58]; score 1, 17.11 [10.53–26.16]; score 2, 17.20 [11.59–25.15]; score 3, 15.88 [10.51–22.93]; score 4, 16.61 [14.11–22.99]; Figure 1A), or latency (seconds; p = 0.33; score 0, 0.17 [0.11–0.23]; score 1, 0.15 [0.12–0.22]; score 2, 0.18 [0.12–0.27]; score 3, 0.15 [0.12–0.20]; score 4, 0.15 [0.13–0.15]; Figure 1B).

Conclusion: Our approach enables synchronized analysis of subthalamic LFPs and video-based kinematics at individual tap events. Preliminary results show that ERD-ERS amplitude and latency were not associated with clinician-rated FT severity. Future analyses will test associations between beta dynamics and quantitative kinematic metrics, which may clarify the potential of event-related LFPs as physiomarkers for PD.

ERD amplitude (A) and latency (B).

References: 1. Heinrichs-Graham E, Wilson TW, Santamaria PM, Heithoff SK, Torres-Russotto D, Hutter-Saunders JAL, et al. Neuromagnetic Evidence of Abnormal Movement-Related Beta Desynchronization in Parkinson’s Disease. Cerebral Cortex. 2013;24(10):2669–78.
2. Houweling S, Beek PJ, Daffertshofer A. Spectral changes of interhemispheric crosstalk during movement instabilities. Cerebral cortex. 2010;20(11):2605–13.
3. Sarapata G, Hubers D, Beudel M, O’Keeffe J. A Simple Method for Synchronising Rich Kinematic Video Data with Local Field Potentials from DBS Systems. Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation. 2025;18(4):1304–5.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/event-locked-characterization-of-movement-related-beta-modulation-using-synchronized-local-field-potentials-and-video-based-kinematics/