Neocortical SEEG showed no group posterior-to-anterior theta or alpha lead in 58 patients

We tested whether neocortical theta (3–8 Hz) and alpha (8–13 Hz) oscillations in stereo-electroencephalography (SEEG) showed the posterior-to-anterior lead reported in electrocorticography traveling-wave studies. We analyzed 200 s of word encoding per participant from bipolar depth channels in OpenNeuro ds004789, session 0. A plan was written and hashed before signal reading. We included channel pairs without shared contacts, 10–50 mm apart and separated by at least 5 mm on the MNI posterior–anterior axis. In 58 participants meeting inclusion criteria (median 98 channels and 1,198 edges), mean phase slope index (PSI) was +0.0010 in theta (95% CI −0.0010 to +0.0032; 30/58 positive; Holm-adjusted p = 0.76) and +0.0003 in alpha (95% CI −0.0011 to +0.0016; 30/58 positive; Holm-adjusted p = 0.76). Frontal-only, temporal-only, other-axis, and distance-stratified results were not significant (all p ≥ 0.08). A post hoc check found larger absolute PSI than in a list-shift control for 58/58 participants in theta and 56/58 in alpha. Thus, lags were present, but their direction was not consistently posterior-to-anterior across participants. Pairwise PSI is not a planar-wave fit; sparse depth sampling, mixed gyral orientation, task and epilepsy context, and time averaging that can cancel direction changes limit interpretation. Of 280 participants, 88 were attempted before the time limit; 58 met the inclusion rule. Channels labeled “n/a” for region were retained, a deviation from the written plan.

stereo-electroencephalography · phase slope index · traveling waves · theta oscillations · alpha oscillations · word encoding · neocortex