Objective: To map theta- and beta-band activity within the subthalamic nucleus (STN) and examine associations with motor improvement and impulsive behavior in Parkinson’s disease (PD) patients undergoing deep brain stimulation (DBS).

Background: Clinical outcomes following STN-DBS depend on electrode location, with beta activity widely used as a physiological marker of the motor STN. Lower-frequency theta oscillations have been linked to impulsive behavior, yet their spatial distribution and connectivity within the STN remain poorly understood.

Method: In 25 PD patients with bilateral STN-DBS, local field potentials were recorded at 3, 6, and 12 months postoperatively with stimulation turned off. Theta- and beta-band power were

computed, while electrode locations were reconstructed using Lead-DBS. Oscillatory activity was mapped using a voxel-based model, and hotspots for theta- and beta-band activity were determined using a standard probabilistic DBS mapping pipeline. Structural connectivity was assessed via fiber-filtering of structural pathways defined by the FOCUS atlas. Associations with motor improvement (UPDRS-III) and impulsive behavior (QUIP-RS) were evaluated in linear mixed-effects models.

Results: Voxel-based mapping revealed spatially segregated subthalamic hotspots for beta- and theta-band activity, with beta concentrated in the dorsolateral motor region and theta localized in

anteromedial limbic–associative territories. In line with these findings, fiber-filtering suggested increased connectivity to cortical motor areas for beta-band activity and increased connectivity to the prefrontal cortex for theta-band activity. Preliminary analyses suggested that stimulation of the beta hotspot may be associated with improved UPDRS-III outcomes. So far, no relationship has been determined between stimulation of the theta hotspot and changes in QUIP-RS.

Conclusion: Beta- and theta-band activity recorded within the STN relates to anatomically separate subcircuits, with beta linked to motor and theta to associative/limbic networks. Preliminary analyses suggest stimulation of the beta-band hotspot may improve motor function. The role of theta-band activity in impulsivity or other neuropsychiatric disorders warrants further investigation using more direct, task-based outcomes.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/probabilistic-mapping-of-subthalamic-beta-and-theta-subcircuits-reveals-segregated-connectivity-and-deep-brain-stimulation-outcomes-in-parkinsons-disease/