Enhanced source localization accuracy through bidirectional deep brain stimulation (DBS) electrodes: A comparative study with non-invasive EEG methods.

Abstract

Accurate neural source localization from electroencephalography (EEG) remains challenging for deep brain structures. This study investigates whether integrating bidirectional deep brain stimulation (DBS) electrodes with conventional scalp EEG can improve source localization accuracy, particularly under varying signal-to-noise ratio (SNR) conditions. While bidirectional DBS leads support both passive recording and active stimulation-based probing of neural circuits, this study focuses exclusively on passive recording capabilities.

Approach: We evaluated three bidirectional DBS electrode configurations (4-contact, 8-contact, and 40-contact arrays) combined with 72-channel scalp EEG using finite element (FE) method-based forward modeling. An extended Complete Electrode Model (CEM) framework was applied here for the first time to model both scalp and DBS electrodes, incorporating realistic electrode-tissue impedance characteristics and locally refined meshes. Source reconstruction was performed using standardized low-resolution electromagnetic tomography (sLORETA) and dipole scan techniques across three SNR conditions (30dB, 17.5dB, and 5dB). Forward and inverse solutions were computed within the Zeffiro-Interface (ZI) framework using source spaces defined for whole-brain, thalamus, and hippocampus-focused analyses.

Main Results: Integrating bidirectional DBS and scalp EEG electrodes significantly improved source localization accuracy, with improvements strongest in regions proximal to the implanted lead. The 40-contact configuration produced the largest gains, while the 8-contact configuration offered the best balance between accuracy and electrode complexity. Dipole scan achieved near-perfect localization (0.0mm at 30dB), whereas sLORETA remained comparatively stable across broader regional analyses for both single- and two-source scenarios.

Significance: Integrating scalp EEG with bidirectional DBS electrode recordings represents a promising approach for deep brain source localization. The complementary strengths of scalp arrays (broad orientational coverage) and DBS contacts (high-SNR proximal measurements) can be leveraged across source configurations, reconstruction algorithms, and noise conditions. This multimodal strategy holds particular promise for post-implantation epilepsy monitoring, adaptive neuromodulation biomarker discovery, and understanding deep-to-cortical seizure propagation dynamics in patients already receiving DBS therapy.