Near SEEG pairs had more similar 4–13 Hz peaks after gradient removal, with similar distance decay in peak height and aperiodic exponent

In 252 patients with stereo-electroencephalography (SEEG), near bipolar pairs had more similar 4–13 Hz spectral peak frequencies than far pairs after removal of a leave-one-subject-out quadratic MNI location gradient. Across subjects, the mean Spearman correlation between pair-pair distance and absolute residual peak-frequency difference was 0.100 (Fisher z 95% CI 0.085–0.117; one-sided sign-flip p=1e-4, the permutation floor); 207/252 subjects had positive correlations. The near (<20 mm) minus far (≥40 mm) difference was −0.55 Hz (95% CI −0.61 to −0.49; Holm-adjusted p=3e-4; 222/244 subjects negative). At 10–30 mm, same-shaft pairs had 0.14 Hz more similarity than different-shaft pairs. Residual peak height and raw aperiodic exponent also showed distance decay (mean rho 0.106 and 0.140), so the effect was not specific to peak frequency. Data were one 60 s task segment per subject from epilepsy patients; seizure-onset-zone and lesional pairs were retained. Distances used MNI midpoints, and bipolar rereferencing does not eliminate possible volume conduction. The findings support modest local spectral similarity in this sample, while its cause remains unresolved.

stereo-electroencephalography · SEEG · spectral peak frequency · local similarity · distance decay · aperiodic exponent · epilepsy