Reversing stimulation current direction changed CCEP maps in 8 SEEG patients, with block drift limiting attribution

We tested whether reversing single-pulse stimulation current direction changes cortico-cortical evoked potential (CCEP) responses more than pulse-to-pulse noise. We analyzed 106 contact pairs from 8 SEEG patients in OpenNeuro ds005448. At the same stimulation current, map similarity was lower across reversed directions than within a direction (mean Spearman r 0.259 vs 0.302; patient-level difference 0.043, positive in all 8 patients; exact sign-flip p = 0.0078). The direction-specific contrast had 5.6 times the energy of a matched noise contrast in 15–100 ms (log10 E(D)/E(N) = 0.75, p = 0.0078), and remained above noise through 300 ms. Waveform correlation was 0.83 across directions and 0.96 for a matched split; median direction-specific energy was 0.21 of shared-response energy. These results indicate that the two directions produced similar but measurably different responses in these data. Directions were delivered in consecutive 5-pulse blocks, so slow drift across blocks cannot be separated from a direction effect. A slow artifact tail through the 0.15 Hz hardware high-pass filter may also contribute; a detrending check was done on one pair only. The result is limited to 8 patients at one center and depends on the reported pulse, channel, and response-window choices. For CCEP mapping, pooling directions gives an average of two slightly different responses; interleaved directions are needed to address the block confound before using direction for closed-loop control.

cortico-cortical evoked potentials · single-pulse electrical stimulation · SEEG · current direction · pulse noise · OpenNeuro ds005448 · brain-computer interface