Across 54 SEEG patients, encoding HFA and theta slopes were not significantly related to primacy or recall rate

This between-subject analysis tested whether serial-position slopes in encoding 70–150 Hz high-frequency activity (HFA) or 3–8 Hz theta power were related to behavioural primacy or overall recall in 54 pure-SEEG patients performing FR1 delayed free recall (OpenNeuro ds004789, session 0). It used per-word, sample/fs-timed features for 0–1.6 s epochs and the mean over bipolar pairs. None of four primary Spearman tests was significant after Holm correction: HFA slope versus primacy, rho = +0.26 (95% bootstrap CI −0.03 to +0.53; permutation p = 0.056; Holm p = 0.23); theta slope versus primacy, rho = −0.24 (CI −0.49 to +0.04; p = 0.088; Holm p = 0.23); HFA slope versus recall rate, rho = +0.09 (CI −0.18 to +0.35; p = 0.50; Holm p = 0.50); and theta slope versus recall rate, rho = −0.25 (CI −0.50 to +0.03; p = 0.065; Holm p = 0.23). The primacy associations had signs opposite to their predictions. Thus, the results do not support the prediction that subjects with a steeper HFA decrease have stronger behavioural primacy. At n = 54, estimated power was about 0.8 for |rho| = 0.44 at alpha = 0.0125; smaller effects were not excluded, except that the HFA confidence interval excluded rho below −0.03. Split-half reliability was 0.63–0.90, with maximum observable correlations of 0.70–0.82, so low reliability does not explain the null for moderate or large effects. Exploratory recalled-flag-controlled associations were HFA rho = +0.36 (p = 0.008) and theta rho = −0.30 (p = 0.029), uncorrected; these are not confirmatory claims. Subjects had different clinical electrode coverage, and some contributed only four full lists. The study agrees with the linked within-subject analysis, which reported that HFA mediated 2.2% of primacy.

serial position · free recall · SEEG · high-frequency activity · theta power · primacy effect · between-subject analysis · OpenNeuro ds004789