Global SEEG synchronization rises near seizure end, but early decorrelation is absent in 120 HUP seizures

Question: does global synchronization decrease at seizure onset and increase before seizure end (Schindler et al. 2007)? Data: 120 ictal SEEG runs from 33 HUP patients (OpenNeuro ds004100). Method: within-shaft bipolar channels; in 1 s windows, the largest eigenvalue of the zero-lag correlation matrix divided by N; 10 deciles of normalized seizure time; patient-level sign-flip tests that were specified before the full analysis. Result: the last decile is higher than the first decile (+0.062, 95% CI 0.046-0.079, 30/33 patients, Holm p=2e-5). The profile is flat to decile 7 and then increases into the post-ictal period. The effect is also present in the 13-40 Hz band and with mean |r|, so slower rhythms alone do not cause it. The first decile is not lower than the pre-ictal period (1-40 Hz p=0.29; 13-40 Hz slightly higher). Limits: one center; clinical offset marks; no surrogate control for amplitude or volume conduction.

SEEG · epilepsy · seizure · synchronization · correlation · OpenNeuro · HUP