ENHANCED SOURCE LOCALIZATION ACCURACY THROUGH BIDIRECTIONAL DBS ELECTRODES: A COMPARATIVE STUDY WITH SCALP EEG

Accurate neural source localisation remains a fundamental challenge in electroencephalography (EEG), particularly for deep brain structures that are difficult to reconstruct using conventional scalp-based methods. Bidirectional deep brain stimulation (DBS) provides a promising complementary approach by enabling simultaneous recording and stimulation through the same electrodes. This study investigates the impact of bidirectional-DBS electrode configurations, alone and in combination with traditional scalp-EEG, on neural source localisation accuracy across different signal-to-noise ratio (SNR) conditions. We evaluated three bidirectional-DBS electrode configurations (4-, 8-, and 40-contact arrays) in conjunction with a 72-channel scalp-EEG system. Source reconstruction was performed using standardised low-resolution electromagnetic tomography (sLORETA) and dipole scan techniques under three SNR conditions (30, 17.5, and 5 dB). Forward and inverse solutions were computed using finite element method implementations with mesh refinement, incorporating bidirectional current flow modelling through an extended Complete Electrode Model framework. Integrating bidirectional-DBS and scalp-EEG significantly improved localisation accuracy, with error reductions of up to 97.4% for thalamic sources under low-SNR conditions. While scalp-EEG achieved accurate orientation estimates at high-SNR (angular error: 36.3° ± 5.3°), performance degraded substantially with increasing noise. In contrast, the 40-contact bidirectional-DBS configuration maintained robust performance across all SNR levels, achieving sub-millimeter accuracy (0.0 ± 0.0 mm) at 30dB SNR using dipole scan. Overall, bidirectional-DBS enhanced localisation performance under challenging noise conditions, where proximity to the source outweighed the orientational coverage advantages of scalp electrodes. These findings demonstrate that integrating scalp-EEG and bidirectional-DBS represents a transformative approach for improving deep brain source localisation.