Residual theta did not significantly shift toward slow theta for recalled words in FR1 SEEG

We tested whether residual theta in encoding spectra shifts toward slow theta for later-recalled words after removal of aperiodic 1/f structure. We analyzed archived condition-mean spectra from 49 FR1 SEEG subjects (session 0; 4,584 bipolar pairs, including 231 hippocampal pairs) in OpenNeuro ds004789. Across all pairs, the mean shift index difference was +0.0029 log10 (95% CI −0.0033 to +0.0088; Holm p = 0.35); in hippocampus it was +0.0134 (95% CI −0.0007 to +0.0273; Holm p = 0.13). Neither prespecified test was significant. The hippocampal estimate had the predicted direction, and the fast-theta residual decrease was nominally significant without correction, so a small hippocampal shift (up to about 0.27 dB) is not excluded. The analysis used condition means, one dataset and a fixed 1.6 s window; it could not control serial position or test words individually.

theta oscillations · subsequent memory effect · free recall · SEEG · hippocampus · aperiodic spectrum · memory encoding