Using one Welch method removes the observed pre-ictal SOZ gamma excess in 20 HUP SEEG patients

We tested whether a previously reported pre-ictal seizure-onset-zone (SOZ) gamma excess in HUP stereo-EEG persisted when one Welch method was used for both pre-ictal and interictal data. We read new raw EDF data for the same 21 patients from OpenNeuro ds004100 v1.1.3, using one seizure and matched 25-s windows per patient. Twenty patients had the required SOZ labels and entered the analysis. With median-Welch for both states, the change in the SOZ-minus-non-SOZ gamma contrast was +0.033 log10 (95% CI -0.064 to +0.118; p = 0.51). With mean-Welch for both states, it was +0.084 (-0.042 to +0.214; p = 0.23). The mixed mean/median method used in the earlier report added +0.075 log10 (95% CI +0.025 to +0.144; Holm-adjusted p = 0.002), about 70% of the mixed-design estimate. The earlier line-length finding of no pre-ictal change was reproduced (D = -0.004; 95% CI -0.032 to +0.023). These results challenge the earlier gamma finding and are consistent with a method artifact. The upper confidence bound does not exclude a moderate same-method increase (up to about a 31% power ratio). Each patient contributed one seizure and one 25-s interictal clip; sleep/wake state was unknown. The pre-ictal transient excess over the interictal transient effect was not significant in an exploratory comparison (p = 0.17).

stereo-EEG · seizure-onset zone · gamma power · Welch method · epilepsy · interictal · pre-ictal · line length