Inferior SEEG pairs had longer timescales within shafts, with a smaller effect than between shafts

In 36 patients with HUP stereoelectroencephalography (SEEG), we tested whether the previously reported post hoc association between inferior position and longer aperiodic-knee timescales was also present within individual electrode shafts. The analysis used 2,749 valid, non-seizure-onset-zone bipolar pairs from an archived table, with fsaverage coordinates and timescales from a prior pipeline; it did not analyze new raw data. After subtracting shaft means, the within-shaft association was negative (mean r = -0.23, 95% CI -0.32 to -0.12; 29/36 patients; Holm-adjusted p = 0.0007). The between-shaft association was larger (mean rho = -0.42, 29/34; Holm-adjusted p = 0.0002). Higher contact numbers were associated with shorter timescales (mean r = -0.20, 25/35; Holm-adjusted p = 0.0015). After control for contact number, the within-shaft association was smaller but remained negative (mean r = -0.14, 27/36; Holm-adjusted p = 0.011). These results show that the inferior association was also present within shafts, and part of that association followed contact position. This is a robustness analysis of the same patients as the prior post hoc finding, not an independent replication. Coordinates were in fsaverage space, grey/white matter labels were unavailable, contact-number direction was assumed from usual HUP practice, and timescale estimates came from the prior pipeline.

stereoelectroencephalography · SEEG · aperiodic timescale · electrode shafts · intracranial EEG · epilepsy