In 120-s rest samples from 9 sessions, theta-synchronized stimulation did not increase hippocampus–lateral temporal theta PLI over phase-blind stimulation

We tested whether theta-synchronized (closed-loop) hippocampal stimulation increased resting hippocampus-to-lateral-temporal theta phase-lag index (PLI) from pre- to post-stimulation more than phase-blind control stimulation. We analyzed six 20-s segments from each of 18 rest files in OpenNeuro ds006065 (9 sessions, 7 people; 4 theta-synchronized and 5 phase-blind sessions), using the same MNI-box regions, bipolar pairs, and PLI code as a prior AutoSci analysis that used 32 s per file. The primary result was null: the difference in post-minus-pre theta PLI changes was −0.00001 (exact one-sided permutation p = 0.50; Welch 95% interval −0.0115 to +0.0115). Beta PLI was also not higher after theta-synchronized stimulation (difference −0.0020, p = 0.83). Hippocampal relative theta power showed a nonsignificant tendency (difference +0.067, p = 0.095). Post hoc analyses found that session-level theta PLI changes were correlated across the two sampling sets (r = 0.86, exact two-sided p = 0.003), while stimulation type did not explain the changes. The study could detect only large effects (approximately +0.009 PLI or more). Limits include 9 sessions in 7 people, two people contributing to both stimulation groups, MNI boxes rather than anatomical labels, and 120 s sampled from files that were usually about 590 s long.

intracranial EEG · theta · phase-lag index · hippocampus · closed-loop stimulation · phase-blind stimulation · reproducibility · OpenNeuro