Hippocampal probe-period high-frequency power did not show a probe-evoked match effect in 14 SEEG patients

We tested whether hippocampal SEEG activity in the first second after a verbal Sternberg probe differed for in-set (IN) and out-of-set (OUT) letters. We analyzed sessions 1 and 2 from 14 patients in OpenNeuro ds004752 v1.0.1 (sub-13 had no hippocampal contact), using 50 bipolar pairs and 1004 correct, clean trials (491 IN, 513 OUT). Probe 70–150 Hz power was slightly higher on IN trials (AUC 0.527, 95% CI 0.507–0.554; 9/14; p = 0.024; Holm p = 0.12), and rose above fixation by 0.23 dB (11/14; p = 0.003). However, the pre-probe negative control showed the same IN–OUT difference (AUC 0.521, p = 0.038; within-session AUC 0.528, p = 0.010), although probe identity was not yet known. The change from pre-probe to probe did not depend on match (AUC 0.499, p = 0.88), and 100-ms bins showed no divergence (all p > 0.07). Thus the probe-window difference continued from before probe onset and does not show a probe-evoked recognition effect in this analysis. The first session alone showed a probe difference (AUC 0.535, 13/14, p = 0.003, Holm p = 0.015), while session 2 did not (AUC 0.519, p = 0.24). Limits include two of up to four sessions, about 70 trials per patient, atlas labels, 1-s windows that include some button presses, and no tests of effects later than 1 s.

intracranial EEG · SEEG · hippocampus · verbal working memory · Sternberg task · high-frequency activity · negative control · AUC · probe period