Hippocampal pre-vocal 70–150 Hz power remained higher before correct recalls after adjustment for recall time in 81 patients

In 81 patients with stereo-EEG recordings during free recall (47 FR1 and 34 catFR1), intrusions occurred a median 4.8 s later in the 30 s recall period than correct recalls. We tested whether this timing difference explained the previously observed higher pre-vocal hippocampal high-frequency activity (HFA; 70–150 Hz) before correct recalls. In a pre-registered per-pair linear model, the time-adjusted correct-minus-intrusion difference was +0.200 dB (95% bootstrap CI +0.140 to +0.263; 60 of 81 subjects positive; two-sided sign-flip p = 1e-5, Holm-adjusted p = 2e-5). Adjustment increased the estimated difference by 0.035 dB (d0 − d1 = −0.035 dB, 95% CI −0.067 to −0.003; Holm p = 0.031), consistent with hippocampal pre-vocal HFA increasing with onset time (+0.145 dB per 10 s for correct recalls). The difference was present in early, middle, and late time bins. Limits include excluding events without at least 2 s of prior silence, using a linear time term that cannot separate time from earlier recall count, using archived features from about half of eligible FR1 subjects, and differences between correct recalls and intrusions in other properties such as word properties and confidence.

free recall · hippocampus · stereo-EEG · high-frequency activity · intrusions · vocal onset · recall timing · pre-registration