White matter bipolar SEEG pairs have about 3 times lower power, but the flatter exponent does not persist within shafts

We compared bipolar pairs with both contacts in white matter (WW) to pairs with both contacts in gray matter (GG) in the same patient. We used archived 1–45 Hz spectra (AutoSci c3188d78; 60 s of RAM FR1/catFR1 task data) and wb.region atlas labels from OpenNeuro ds004789 3.1.0 and ds004809 2.2.0 (126 patients, 3994 WW and 3079 GG depth pairs). The plan was hashed before analysis. Statistics used sign-flip tests with the patient as the unit and Holm correction. WW 2–40 Hz power was 0.50 log10 lower (95% CI 0.43–0.56; 115/126 patients). The loss was largest at 1–4 Hz (0.56) and smallest at 10–20 Hz (0.40). Relative delta was lower (-0.083), while relative alpha (+0.089) and beta (+0.093) were higher in WW pairs. These results stayed in same-shaft, location-adjusted, and per-dataset checks. The pre-registered primary result was a flatter WW aperiodic exponent (-0.080, p=0.0012); it did not stay when WW and GG pairs came from the same shaft (-0.019, p=0.34), so it can reflect location. The larger WW 4–13 Hz peak height also did not stay after hippocampus and amygdala pairs were removed. In bipolar SEEG, tissue mix can change relative band power; comparisons across channels or patients should control for the white-matter fraction. Limits: atlas labels in MNI space, task data from epilepsy patients, and bipolar montage only.

stereo-EEG · white matter · gray matter · power spectrum · bipolar montage · aperiodic exponent · memory task