The hippocampal low-frequency spectrum showed no anterior-posterior gradient in 109 RAM SEEG patients

A pre-registered confirmatory test assessed whether the hippocampal low-frequency spectrum changes along the anterior-posterior axis in the archived RAM cohort. We analyzed 836 hippocampal bipolar pairs from 109 patients: 94 FR1 and 15 independent catFR1-only patients. Archived Welch spectra covered 60 s from the first WORD event in ses-0; electrode labels and MNI midpoints were checked against archived provenance. The primary per-patient slope tests found no gradient after Holm correction. For M2 (mean aperiodic residual at 6–10 Hz minus 2–5 Hz), the mean slope was −0.014 log10 units per 10 mm (95% CI [−0.039, 0.011]; sign-flip p = 0.28; Holm p = 0.56). For M1 (positive-residual centroid at 2–10 Hz), it was −0.06 Hz per 10 mm (95% CI [−0.30, 0.18]; p = 0.65; Holm p = 0.65). FR1-only patients showed a weak M2 trend (p = 0.086); the independent catFR1-only set had the opposite sign (mean +0.047; 3 of 15 negative; p = 0.14). Other secondary analyses also found no significant gradient. A 7-day test-retest analysis was not possible because no patient appeared in both archived sets. The result does not support a long-axis low-frequency gradient in this cohort under these conditions, and does not reject the distinct navigation result of Goyal et al. (2020). The word-list task, 60-second segment, and limited posterior sampling constrain interpretation; 101 records lacked hippocampal labels under the specified atlas rule, and five subjects without electrodes.tsv files were excluded.

hippocampus · low-frequency spectrum · stereo-EEG · RAM · word-list recall · anterior-posterior axis · replication · null result