The polarity-invariant SEEG response did not decrease relative to artifact during alternating-polarity trains in 7 patients

Across 12 five-second, 43.2 Hz alternating-polarity stimulation trains from 7 patients in OpenNeuro ds006519, the primary comparison found no difference between change in the polarity-invariant pulse response (S, assumed neural) and the polarity-reversing response (D, assumed artifact): mean contrast +0.008, exact two-sided patient-level sign-flip p = 0.86, with 3 of 7 patient means negative. The median S and D ratios also remained approximately constant. In channels selected as responsive from the first second, S decreased (mean log ratio -0.205, p = 0.031), but the S-D contrast was not significant (p = 0.063), and this selection is biased toward a downward change. Selection from the independent middle second gave a smaller, non-significant S decrease (-0.148, p = 0.078). Interpretation is limited by 7 patients, low S-to-noise ratios in most trains, correlations between first-second S and D across channels, and clinical labels restricted to deficit (one blockage+deficit). S may contain artifact residue or shared volume conduction. The findings apply only to this clinical protocol.

SEEG · intracranial EEG · alternating-polarity stimulation · neural response · stimulation artifact · adaptation · sign-flip test