In 36 HUP SEEG patients, bipolar correlation was near zero past nearest same-shaft pairs; high-gamma did not decay faster than delta with recorded reference (20–90 s clips)

We measured how zero-lag correlation between SEEG contacts changes with separation, frequency band and montage. We used one interictal clip of 20-90 s from each of 36 patients in OpenNeuro ds004100 (HUP). We wrote the plan before we read signals. With the recorded reference, mean r was more than 0.3 at more than 40 mm in all bands. High-gamma (65-115 Hz) correlation did not decay faster than delta (1-4 Hz) correlation. The normalized excess at step 3 was 0.052 higher for high gamma (95% CI 0.014 to 0.092, Holm p = 0.014). This result is opposite to our prediction. Common average reference made far correlation negative (about -0.08) and kept r above 0.1 up to about 30-40 mm. With a bipolar montage, the mean same-shaft r of the nearest non-overlapping pairs was near zero in all bands (delta 0.010, high gamma -0.046; difference -0.056, Holm p = 0.00015). Between shafts, bipolar delta |r| at 20-40 mm was 0.055 higher than at more than 60 mm in 35 of 35 patients. The mean r was small (0.01-0.03). Distances between shafts use template coordinates. The band-pass filter was an FFT filter, not the planned Butterworth filter.

SEEG · zero-lag correlation · stereo-EEG · montage · frequency bands · epilepsy