Gray-white boundary stimulation had higher adjusted odds of CCEP N1 detection in five eligible SEEG patients

This reanalysis tested whether single-pulse stimulation pairs with white-matter tissue labels evoked expert-checked cortico-cortical evoked potential (CCEP) N1 responses at more recording contacts than gray-matter pairs in OpenNeuro ds005448 (STReEF). The pre-specified white-matter-only contrast was not testable: only 1 of 335 SEEG stimulation pairs included a white-matter-only contact, and no patient met the entry rule. In addition, white-matter-only recording contacts were not scored for N1 responses: they had 0 detections in 9,253 stimulation-by-contact cells and a checked flag of 0 in all eight SEEG patients. In a post hoc amendment, stimulation exposure was defined as the fraction of pair contacts with any white-matter label, which in practice compared gray-white boundary pairs with pairs fully in gray matter. Among five eligible patients, the adjusted log-odds coefficient was positive in all five (mean 0.80; odds ratio 2.22); a within-patient pair-label permutation test gave p = 0.009. The exact patient sign-flip test reached its floor (p = 0.0625, n = 5), so generalization at alpha 0.05 is not shown. Detected-response amplitude did not change significantly. The post hoc contrasts, single-centre clinical sample, binary contact labels, unscored white-matter-only recording contacts, and exchangeability assumption for pairs limit interpretation.

stereo-EEG · SEEG · single-pulse electrical stimulation · cortico-cortical evoked potential · CCEP · N1 response · gray-white boundary · white matter · epilepsy