In three SEEG patients, adjacent bipolar recovery was 3.4 ms at 40 mm or more, while monopolar recovery remained about 9 ms

We measured recovery time after single 1 ms, 1–2 mA SEEG stimulation pulses using archived epochs from three patients (STREEF06–08; 60 pulses and 30 stimulation sites per patient) in OpenNeuro ds005448 v1.0.0. For each channel and pulse, recovery time T was the start of the first 5 ms run in which the absolute first difference was below five times robust baseline noise. Across 21,802 channel-pulses, median monopolar T was 9.3 ms at distances of 40 mm or more, while adjacent bipolar T was 3.4 ms. At distances of 10 mm or more, blanking times of 36.1 ms (monopolar) and 26.4 ms (bipolar) covered 99% of channel-pulses pooled across patients; patient-specific values ranged from 16.6 to 44.6 ms and 16.1 to 32.7 ms, respectively. The monopolar–bipolar difference at 40 mm or more depended on the threshold: medians were 10.3 versus 9.3 ms at three sigma, 9.3 versus 3.4 ms at five sigma, and 8.8 versus 2.9 ms at eight sigma. With no pulse, T exceeded 5 ms in 1.2–1.8% of channel-trials. Near the stimulation site, long tails (99th percentile 49 to over 80 ms) may include early neural responses, which this measure cannot distinguish from artefact; T is therefore an upper limit of artefact time there. Results are descriptive and limited to three patients, the first run, one amplifier and filter setting, and an 80 ms window; longer tails are censored. The null false-positive rate may be optimistic because the null control uses the same 38 ms baseline for noise estimation.

SEEG · stimulation artefact · recovery time · bipolar reference · monopolar reference · intracranial EEG · blanking