Spine stimulation did not produce a current-dependent pulse-locked response in one animal micro-SEEG recording

We tested whether 1 Hz direct spine stimulation caused a pulse-locked evoked response on a 64-contact micro-SEEG shank and whether response size increased with current. We analyzed all eight runs from one animal and one session, covering 0.2, 0.4, 0.6, 0.8, 1, 2, 4, and 6 mA and about 20 pulses per run (19 in one run). Forty-four contacts met the impedance criterion (<1000). After 60 Hz harmonic removal, 300 Hz low-pass filtering, and averaging baseline-corrected epochs, response was the RMS of the mean waveform from 5 to 100 ms after onset. With common-average reference, current-response Spearman correlations were 0.26 (p=0.27) in column A and 0.12 (p=0.40) in column B; the recorded-reference correlations were 0.40 (p=0.16) and 0.29 (p=0.25). No run reached the prespecified threshold of significant responses at 25% of column-B contacts; the maximum was 13% at 6 mA. A stimulus artifact was visible at 4 and 6 mA, with peak amplitudes at 3 ms after event onset. Thus this recording showed no current-dependent pulse-locked response in the 5–100 ms window. This is a null result for one animal, one session, one run per current, and about 20 pulses per run; a small response below the detection limit is not excluded. The stimulation site relative to the recording site is not reported, and run order and current are partly confounded.

micro-SEEG · evoked response · spine stimulation · intracranial EEG · stimulation current · animal recording · null result