Ictal gamma increase shows preferential localization to seizure onset contacts in stereoelectroencephalography.

Objective: To quantify ictal gamma dynamics in a large stereoelectroencephalography (SEEG) dataset and determine whether ictal gamma increase is preferentially associated with seizure onset zone (SOZ) contacts. Methods: Seizures from the public OpenNeuro dataset ds004100 were analyzed. Gamma-band activity (30-80 Hz) was quantified for each contact as the log2-transformed ratio of ictal gamma power to 5-min preictal baseline power. Gamma dynamics were summarized at the contact, seizure, and patient levels. SOZ-related differences were evaluated using pooled descriptive comparisons, within-patient analyses, and hierarchical mixed-effects modeling. We also tested whether the top 10% gamma contacts within each seizure were enriched in SOZ contacts and performed coordinate-informed region-stratified analyses. Results: A total of 16,262 contacts, 138 seizures, and 36 patients were included. SOZ contacts showed higher gamma log-ratio values than non-SOZ contacts (median 1.838 vs. 0.696, Conclusion: Ictal gamma activity increases during seizures and is consistently associated with seizure onset contacts, with anatomically non-uniform SOZ-related effects across sampled regions. Significance: These findings suggest that ictal gamma increase may provide spatially informative electrophysiological information related to seizure onset contacts in intracranial recordings.