Hippocampal high-frequency activity did not distinguish match from non-match probes in 14 patients across two sessions

We tested whether hippocampal high-frequency activity (HFA, 70–145 Hz) in the 0.1–0.8 s after a verbal Sternberg probe differed between non-match (OUT) and match (IN) probes in 14 patients with hippocampal SEEG pairs. The pre-specified measure was mean log10 HFA from 6.1–6.8 s minus a 5.5–6.0 s baseline, with set size controlled and patient-level Mann–Whitney AUCs tested by an exact two-sided sign-flip test. Session 1 mean AUC was 0.510 (7/14 patients above 0.5, p = 0.40); session 2 was 0.479 (4/14, p = 0.11); combined AUC was 0.495 (95% CI 0.476–0.511, p = 0.59). The two sessions pointed in opposite directions, and patient AUCs correlated at r = 0.20. The probe itself increased hippocampal HFA in both sessions (+0.012 log10, p = 0.0013; +0.011, p = 0.028), while match status did not. With about 10–30 correct trials per probe type and patient, small effects may have been missed. Other limits include atlas-based electrode labels, testing HFA only, using only sessions 1 and 2, and using familiar letters as probes; the result does not test item novelty.

hippocampus · high-frequency activity · SEEG · verbal working memory · Sternberg task · match and non-match · intracranial EEG · replication