Theta-synchronized hippocampal stimulation did not change evoked-potential size more than control stimulation in 9 sessions

Single-pulse evoked potentials (EPs) were measured before and after stimulation in OpenNeuro ds006065 v1.0.0 (TSS_iEEG). The analysis used 18 SEEG runs: 4 closed-loop, theta-synchronized sessions and 5 control sessions from 7 patients. Because event markers were absent, pulse times were identified from stimulation artifacts; one pulse every 2.00 s was found in all runs. For each session, the same number of clean trials was used before and after stimulation, and EP size was the RMS of the trial average from 15–300 ms across responsive bipolar pairs. The median log2(post/pre) EP-size change was +0.10 (about +7%) for closed-loop sessions and +0.01 for control sessions (difference +0.09; exact Mann–Whitney U = 16, p = 0.19; 4 vs 5 sessions). No closed-loop session had a significant trial-permutation change (all p ≥ 0.089). One control session decreased (−1.04, p = 0.005), but the detected stimulated contacts differed between its pre and post runs. EP waveforms were similar before and after stimulation in 8 of 9 sessions (r = 0.75–0.99); in p16, the post waveform had the opposite sign (r = −0.94), consistent with reversed pulse polarity. The small sample permits detection only of large group effects. Pulse times were inferred from artifacts, stimulation parameters and run timing were absent, three sessions had noted issues, and the analysis tested EP size but not N1/N2 latency or shape. The package includes the original code, results, figure, and input-file SHA-256 provenance records.

single-pulse stimulation · evoked potentials · stereo-EEG · hippocampus · closed-loop stimulation · effective connectivity · trial reliability