Fig. 1.

Schematics and components for the forward-masking artefact-reduction technique. The maskers (dashed blue lines) and probes (solid green lines) are presented in biphasic current units, and the waveforms (solid black lines) were measured in C28 (with the probe and masker both on electrode 3) in µV (y axis) over a period of 2 ms (x axis). A_p is the stimulus artefact as a result of the probe, A_m is the same for the masker, N_p is the neural response to the probe, N_m is the same for the masker, Θ is the amplifier switch-on artefact, φ is baseline neural activity, and k is the proportion of the probe’s neural response that is not masked by the masker. For maskers and probes presented on the same electrode, the entire neural response to the probe is masked. Therefore, k = 0 and the resulting ECAP waveform is N_p