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

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.

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.

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, p = 9.46 × 10^-23). In hierarchical mixed-effects modeling, SOZ status remained significantly associated with higher contact-level gamma log-ratio values (β = 0.802, 95% CI 0.739 to 0.864, p < 2 × 10^-16). Top-gamma contacts were enriched in SOZ contacts (28.8% vs. 6.7%, odds ratio 5.65, p = 2.92 × 10^-123). Region-stratified analyses showed the strongest SOZ versus non-SOZ separation in mesial temporal contacts, with additional significant differences in lateral temporal, insular, parietal, and central sensorimotor regions.

Ictal gamma activity increases during seizures and is consistently associated with seizure onset contacts, with anatomically non-uniform SOZ-related effects across sampled regions.

These findings suggest that ictal gamma increase may provide spatially informative electrophysiological information related to seizure onset contacts in intracranial recordings.