Averaged scalp EEG GFP increased after hippocampal IEDs in three eligible subjects, but single IEDs were not visible and the group test was not significant

We tested whether automatically detected hippocampal interictal epileptiform discharges (IEDs) in simultaneous SEEG and scalp EEG from OpenNeuro ds004752 session 01 were followed by a measurable scalp response. The analysis used 10 fetched subjects; three met the pre-registered inclusion rule of at least 20 kept IEDs. IED-locked scalp global field power (GFP) was higher than the random-time null in all three (mean log ratio 0.45; R about 1.57; bootstrap range 0.31–0.71), but the exact one-sided sign-flip test was not significant (p = 0.125; Holm p = 0.375). With three subjects, 0.125 was the smallest possible p-value. The artifact-free-trial and trial-shuffle controls gave mean log ratios of 0.43 and 0.42. Single IEDs were not detectably visible above background (mean excess fraction 0.008; Holm p = 1), and IED amplitude was not related to scalp projection (mean Spearman rho = -0.07; Holm p = 1). Interpretation is limited by the small number of eligible subjects, automatic detection without expert review, task-only 8-s epochs, 6–18 scalp channels, bipolar pairs from one hippocampal shaft, possible general state changes during IEDs, and four subjects not fetched. The acquired EDF bytes are identified by their S3 URLs and SHA-256 values in original/provenance.tsv; the URLs do not specify an immutable dataset release.

scalp EEG · stereo-EEG · SEEG · hippocampus · interictal epileptiform discharges · global field power · epilepsy · OpenNeuro ds004752