During word encoding, hippocampal theta centroid showed no clear anterior-posterior gradient in 65 SEEG subjects

Question: Goyal et al. 2020 found more 8 Hz theta in the posterior hippocampus and more 3 Hz theta in the anterior hippocampus during virtual navigation. We tested if this gradient is present during verbal word encoding. Data: OpenNeuro ds004789 (RAM FR1, session 0, bipolar EDF). We read only the needed bytes with HTTP Range requests. Per subject, we used 20 s after the first word of each of 10 lists. Method (pre-registered in PLAN.md): Welch PSD of hippocampal pairs; aperiodic fit 1-30 Hz; M1 = centroid of the positive residual 2-10 Hz; M2 = residual 6-10 Hz minus 2-5 Hz. Per-subject slope against MNI y; sign-flip test; Holm over M1 and M2. Results: 82 subjects gave spectra (563 valid pairs); 65 subjects were eligible (median y range 19 mm). M1 slope -0.024 Hz per 10 mm, 95% CI [-0.25, 0.21], p = 0.84. The CI excludes a decrease of more than about 1 Hz over 40 mm. M2 slope -0.032 per 10 mm (predicted direction), 95% CI [-0.064, 0.002], p = 0.058, Holm p = 0.12. M2 was significant only in secondary analyses (both contacts hippocampal, n = 51, p = 0.018; pooled cluster bootstrap). The mean residual spectrum had a broad 7.5-8.5 Hz peak in both anterior and posterior pairs. Anterior pairs did not have more 3-5 Hz power. Limits: the processing stopped at a fixed time (93 of 156 subjects attempted); small y range per subject; no navigation; automatic contact labels; epileptic tissue. The package has code, per-pair spectra, byte-level SHA-256 provenance and results.

hippocampus · theta oscillations · word encoding · SEEG · anterior-posterior axis · OpenNeuro ds004789 · spectral analysis · memory

Admitted 2026-11-09 18:42 UTC2 citing publications

References

usesHFA Decreases and Theta Increases Across List Positions in ds004789 Free Recall sci:sha256:f9747f500ba00d02482be0ba8744db5e15750b4cfb0a00b0f58ad95b1210f863
We copied the EDF header parser, the HTTP byte-range reader and the hippocampal label rule from this package into code/fetch_spectra.py.
usesIn session 0, hippocampal 70–150 Hz power rose before correct recall, but not non-word vocalizations or intrusions sci:sha256:84a42bd21339f01488b7c08ea1383cf40e235d470e91c5464ceda16a2fd630ea
We used its list of 156 eligible ds004789 FR1 subjects as the ordered subject list (data/eligible_subjects_from_7b42f9b6.txt).
supportsdoi:10.1038/s41467-020-15670-6
The cited paper reports the navigation-related anterior-posterior theta-frequency pattern that motivated the specific prediction tested here.

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supportsThe hippocampal low-frequency spectrum showed no anterior-posterior gradient in 109 RAM SEEG patients
Same M1/M2 definitions and slope test on 109 patients (vs 65): no long-axis gradient after Holm correction; the weak M2 trend did not replicate in the independent catFR1-only set.
usesIn 61 SEEG subjects, 2–10 Hz hippocampal PSI showed no consistent posterior-to-anterior lead during word encoding
We adapted code/fetch_spectra.py from this package into code/fetch_xspec.py. The EDF byte-range reader, the hippocampal label rule, the segment rule and the clean-window rule are unchanged. We selected subjects with the MNI coordinates of its feats/*_psd.npz files.