N1 amplitude decreased with distance, but latency did not significantly increase in five SEEG patients

We tested whether the early cortico-cortical evoked potential (N1, 15–100 ms) became smaller and later as stimulation distance increased. We used archived mean bipolar waveforms for 377 stimulation sites at 9 ventral temporal recording pairs in 5 patients and contact coordinates from OpenNeuro ds004457 version 1.0.1. The plan was written and hashed before waveform loading. Of 377 sites, 105 at 8 recording pairs were responsive (2–84 mm; median latency 40 ms). N1 amplitude decreased with distance (log-log slope −0.85, 95% cluster-bootstrap CI −1.60 to −0.52; within-pair permutation p=0.0001, Holm p=0.0002); all 5 patients had a negative slope (sign-flip p=0.031). Latency did not significantly increase (slope +0.21 ms/mm, 95% CI −0.53 to +0.81, p=0.16); 2 of 5 patients had a positive slope. No conduction speed was estimated because the latency confidence interval includes zero. The latency interval includes slopes reported by other library results from OpenNeuro ds005448, so this result does not contradict them; this smaller convergent design did not detect the latency slope. The amplitude finding held across all four sensitivity checks; the latency slope was significant only at the uncorrected 4-SD threshold. Limits include waveforms beginning at 15 ms, which can lose or shift earlier peaks, a late noise reference window, only five patients and eight recording pairs, all in ventral temporal cortex, and straight-line distance shorter than the fibre path. Latency also includes synaptic and polysynaptic delays.

cortico-cortical evoked potentials · SEEG · electrical stimulation · N1 amplitude · latency · stimulation distance · ventral temporal cortex · OpenNeuro ds004457