Cochlear implant artifact rejection in electrically evoked auditory steady state responses

Electrically evoked auditory steady state responses (EASSRs) are EEG signals measured in response to periodic or modulated pulse trains presented through a cochlear implant (CI). EASSRs are studied for the objective fitting of CIs in infants, as electrophysiological thresholds determined with EASSRs correlate well with behavioural thresholds. Currently available techniques to remove CI artifacts from such measurements are only able to deal with artifacts for low-rate pulse trains or modulated pulse trains presented in bipolar mode, which are not used in main clinical practice. In this paper, an automatic EASSR CI artifact rejection technique based on independent component analysis (ICA) is presented that is suitable for clinical parameters. Artifactual independent components are selected based on the spectral amplitude of the pulse rate. Electrophysiological thresholds determined based on ICA compensated signals are equal to those detected using blanked signals, but measurements at only one modulation frequency are required.