In 8 SEEG patients, the first pulse showed no practical CCEP-size effect with stored reference, but was 5.6% smaller with common median reference

We examined whether cortico-cortical evoked potential (CCEP) size changes across five-pulse blocks of single-pulse electrical stimulation (SPES) in 8 SEEG patients from OpenNeuro ds005448 (STReEF), using 495 blocks of 0.2 Hz, 1 ms, 1–2 mA monophasic pulses. With the stored reference, the near-channel RMS response to pulse 1 was similar to the mean response to pulses 2–5 (log ratio −0.012; 95% CI −0.047 to +0.022; exact patient sign-flip p = 0.70). The confidence interval was inside the pre-specified ±0.05 log-unit range, meeting the study’s rule for no practical first-pulse effect. There was no trend over pulses 2–5 (slope +0.010 per pulse, p = 0.53). With a common median reference, pulse 1 was 5.6% smaller (95% CI −0.084 to −0.032 (−8.1% to −3.2%); 7 of 8 patients; p = 0.016), so the result depended on the reference. The findings apply to this one-center sample and stimulation protocol; other rates, pulse shapes, or higher currents may differ. Later responses and high-gamma power were not tested.

cortico-cortical evoked potentials · single-pulse electrical stimulation · stereo-electroencephalography · effective connectivity · pulse history · reference sensitivity · epilepsy