Objective: In the present study, we aimed to: (1) isolate the motor cortical EEG activity responsible for translating subthalamic nucleus (STN) beta hypersynchrony into bradykinesia; and (2) reconstruct STN beta activity using deep source analysis of high-density EEG (hdEEG).

Background: Several beta features have been associated with bradykinesia in Parkinson’s disease (PD), but only STN beta power is a validated correlate. However, invasive STN recordings limit clinical applicability and the specific cortical correlate of STN beta hypersynchrony remains unknown. Recent advances suggested that subcortical sources can be reconstructed from surface hdEEG [1], and Percept-DBS system now enables chronic, artifact-free local field potentials (LFPs) recordings, overcoming limitations of transient, lesion-prone intraoperative recordings.

Method: Fifteen patients with PD chronically implanted with Percept-DBS underwent simultaneous recordings of STN-LFPs/hdEEG at rest and during finger tapping, in ON/OFF stimulation conditions, after 12-hour withdrawal of dopaminergic medication. Movement performance was assessed via kinematic analysis. Source reconstruction was performed using a standard MRI template, OpenMEEG-based forward modeling, dipole modeling inverse solution [1,2]. Cortico-subcortical coherence in the beta range was calculated, and condition-related differences were assessed using cluster-based permutation statistics. Coherence changes were correlated with finger tapping performance.

Results: A significant cluster of difference in high-beta (21–35Hz) cortico-subcortical coherence between ON and OFF DBS conditions was identified in the left motor and supplementary motor area. This cluster revealed a decrease in coherence in ON condition compared to OFF condition. A negative correlation was observed between the loss of beta-band coherence (ON–OFF difference) and clinical improvement, as measured by change in finger tapping performance. We found a correlation between the recorded STNbeta envelope and the reconstructed hdEEG source-signal envelope in the clinically relevant beta change.

Conclusion: HdEEG can be used to identify cortical activity correlated to STN beta hypersynchrony. Our approach opens new avenues for investigating the network mechanisms underlying bradykinesia.

References: [1] Seeber M, Cantonas LM, Hoevels M, Sesia T, Visser-Vandewalle V, Michel CM. Subcortical electrophysiological activity is detectable with high-density EEG source imaging. Nat Commun. 2019;10(1):753.
[2] Gramfort A, Papadopoulo T, Olivi E, Clerc M. OpenMEEG: opensource software for quasistatic bioelectromagnetics. Biomed Eng Online. 2010;9:45.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/developing-non-invasive-eeg-biomarkers-for-parkinsons-disease-using-concurrent-subthalamic-nucleus-cortical-recording-as-ground-truth/