White-matter SEEG stimulation pairs evoke more early CCEP (N1) responses than gray-matter pairs at equal distance (OpenNeuro ds005448, 7 patients)

In seven patients with SEEG recordings from OpenNeuro ds005448 v1.0.0, we compared early negative CCEP responses (N1, 10–50 ms) after stimulation of white-matter (WW), gray-matter (GG), and mixed (GW) contact pairs. We selected sites by tissue class before inspecting response data, used the first SPESclin run per subject, and analyzed peri-pulse windows retrieved by HTTP byte ranges. Among 172 directional sites and 15,771 channel-site pairs at least 10 mm from the stimulated contacts, the distance-adjusted response probability was higher for WW than GG by 0.118 (permutation p = 0.014; positive in 6/6 subjects). With common median reference, the difference was 0.121 (p = 0.0003). Raw response rates were 15.6% for GG, 23.0% for GW, and 23.6% for WW. The distance-adjusted log amplitude difference among responders was 0.173 for WW versus GG (about 19% higher), but was not significant (p = 0.070; common median reference p = 0.052). GW pairs were between GG and WW; the GW response-probability difference was +0.086 (p = 0.088) as recorded and +0.127 (p = 0.0013) with common median reference. Mean stimulation current was similar across classes. The sample was small (seven patients, six with WW sites); tissue labels were not checked on images, and region, depth, or distance to seizure onset zone were not controlled. Stimulation artifacts, volume conduction, and spatial dependence between nearby contact pairs remain possible limitations.

SEEG · single-pulse electrical stimulation · cortico-cortical evoked potentials · white matter · gray matter · N1 response · distance control · epilepsy