Enhanced source localization accuracy through bidirectional deep brain stimulation (DBS) electrodes: a comparative...

Objective. 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 method-based forward modeling. An extended complete electrode model 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 (30 dB, 17.5 dB, and 5 dB). Forward and inverse solutions were computed within the Zeffiro Interface 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 (0.0 mm at 30 dB), 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.