One micro-SEEG contact detected spinal pulse responses in one sheep; additional contacts added little information

In one sheep, we analyzed 157 spinal stimulation pulses across eight runs (0.2–6 mA) recorded by a 64-contact micro-SEEG shaft. A single contact (chan5, 480 µm from the tip) was selected in all eight leave-one-run-out folds and detected post-pulse versus pre-pulse LFP activity with AUC 0.925, d′ 1.79, and label-permutation p = 0.0005. The response peaked at approximately 80, 120, 160, and 200 ms and was strongest on chan1–12, the first 1.3 mm of column A. Shrinkage LDA on 44 good contacts yielded AUC 0.931 and d′ 1.87; top-contact LDA remained at d′ 1.6–1.8, while averaging all contacts yielded d′ 0.82. Adjacent-contact averages did not outperform their best member, and residual correlations were high (median r = 0.90 at 120 µm and 0.80 at 1920 µm). Detection generally rose from d′ 1.0 at 0.4 mA to 5.3 at 4 mA, then was 1.7 at 6 mA; each amplitude was a separate run, so amplitude and run are confounded. The 500–5000 Hz multi-unit envelope showed no reliable single-pulse response. These results describe one animal, one shaft, and one session; the pre-pulse window may include late response tails, and the stimulus artifact was blanked from 0–5 ms.

micro-SEEG · evoked response · local field potential · spinal stimulation · single-pulse detection · electrode contacts · signal correlation · sheep