Acute scalp EEG signatures of anterior thalamic DBS in epilepsy:reproducible gamma power enhancement within an aperiodic spectral-state shift

Background: Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is an established treatment for drug-resistant epilepsy, but acute scalp-EEG signatures of stimulation remain incompletely characterized. Objective: To identify acute scalp-EEG signatures of ANT-DBS and assess their cross-year reproducibility in a proof-of-concept repeated-session cohort. Methods: Scalp EEG from five patients recorded one year apart (10 sessions) was analyzed during nominal cyclic DBS (1 s ON, ~5 s OFF). DBS ON was compared with the within-cycle OFFmean and consecutive post-offset OFF windows using power spectral density (PSD), spatiotemporal-frequency (STF) analysis, and spectral parameterization. Results: DBS ON showed higher 30-70 Hz gamma power than OFFmean in all sessions (median +0.94 dB), with significant PSD clusters overlapping gamma in 10/10 sessions. STF identified gamma increases as the most reproducible spatiotemporal effect. Exploratory frontal 34-44 Hz and central 56-70 Hz components showed cross-year support, and the broader pattern persisted when 48-52 or 45-55 Hz were excluded before clustering. Lower-frequency effects were more heterogeneous and weakened from early to late OFF windows. Aperiodic parameterization showed lower ON exponent and offset in all sessions (Delta chi = -0.20; Delta b = -0.25). After correction, theta suppression was not preserved, whereas a smaller low-gamma residual remained. Conclusions: ANT-DBS was associated with consistent acute scalp-EEG state signatures comprising raw gamma enhancement, lower aperiodic exponent and offset, and a modest residual low-gamma effect. These hypothesis-generating findings show that scalp EEG can capture acute ANT-DBS state changes, while larger prospective studies are needed to establish clinical relevance.