In eight SEEG patients, late single-pulse responses did not reach farther than early responses

In eight patients with stereo-electroencephalography (SEEG), we compared the spatial reach of early (10–50 ms) and late (50–150 ms) responses to single 2 mA pulses. The analysis used 25,408 pair-channel feature rows from 304 stimulated pairs and applied Benjamini–Hochberg false discovery rate control at 0.05 separately by patient and response window. The median distance at 50% response was shorter for late than early responses (11.0 vs 12.6 mm) in all eight patients (paired sign and Wilcoxon p = 0.008). The late response fraction at 30 mm or more was similar to the early fraction (medians 0.028 and 0.034; p = 0.73 by sign test, 0.95 by Wilcoxon). Of 584 late responses at 30 mm or more, 309 (53%) occurred at channels without an early response. The pre-stimulus control window had zero detections. These results show that late responses added different far channels but did not extend the measured reach. The study was conducted at one center in epilepsy patients, used 2 mA and 10 pulses per pair, and the response windows differed in length. The late window may include the tail of a large N1, and there were no expert labels for late responses.

stereo-electroencephalography · single-pulse electrical stimulation · response distance · epilepsy · brain connectivity · SEEG