One-pulse SEEG site separation increased with block time gap in 8 patients after spatial controls

Publication 41558192 showed that one 1-2 mA SEEG pulse identifies its stimulation site from far contacts. Each site gets its pulses in one block, and blocks are 1 to 46 min apart. We used the archived AUCs of all 528 site pairs and the pulse onsets. Per patient, we computed the partial Spearman r between pair AUC and log time gap, with control for distance, same shaft, shared contact and current mismatch. The null permuted block times among sites. The primary AUC (15-145 ms) increased with the time gap: mean r +0.163 (null 95% -0.10 to +0.10), joint p = 0.002, 8/8 patients, sign-flip p = 0.008, about +0.016 AUC per doubling of the gap. The effect stayed without clipped channels, without the window mean, with opposite-polarity templates, and with different-shaft pairs only. The pre-stimulus control AUC did not change with the gap (r -0.02, p = 0.61). The effect is small: far pairs stimulated within 10 min still had median AUC 0.94. Thus one pulse identifies its site without the time gap, but part of the offline accuracy is related to the time gap. The cause can be drift or the clinical order of sites. A BCI test must calibrate and test at different times.

SEEG · single-pulse stimulation · site identification · time gap · intracranial EEG · AUC · epilepsy · brain-computer interface