Electrically evoked auditory steady-state responses (EASSRs) are neural potentials measured in the electroencephalogram (EEG) in response to periodic pulse trains presented, for example, through a cochlear implant (CI). EASSRs could potentially be used for objective CI fitting. However, EEG signals are contaminated with electrical CI artifacts. In this paper, we characterized the CI artifacts for monopolar mode stimulation and evaluated at which pulse rate, linear interpolation over the signal part contaminated with CI artifact is successful.
CI artifacts were characterized by means of their amplitude growth functions and duration.
CI artifact durations were between 0.7 and 1.7 ms, at contralateral recording electrodes. At ipsilateral recording electrodes, CI artifact durations are range from 0.7 to larger than 2 ms.
CI artifact-free EASSRs are crucial for reliable CI fitting and neuroscience research. The CI artifact has been characterized and linear interpolation allows to remove it at contralateral recording electrodes for stimulation at 500 pps.
AGF, amplitude growth function; C, maximum comfortable stimulation level; CI, cochlear implant; d, interpolation duration; D, STIM artifact duration; EABR, electrically evoked auditory brainstem response; (E)ASSRs, (electrically evoked) auditory steady-state responses; ECAP, electrically evoked compound action potential; I, intercept of the CI artifact AGF; ICA, independent component analysis; PCA, principal component analysis; POD, programming device; RF, radio frequency; RF artifact, RF communication link artifact; STIM artifact, electrical stimulation artifact; T, threshold stimulation level; θ, slope of the CI artifact AGF
Cochlear implant (CI); CI stimulation artifacts; Electrically evoked auditory steady-state responses (EASSR); Linear interpolation; Monopolar mode stimulation
Citation: Hanne Deprez, Robin Gransier, Michael Hofmann, Astrid van Wieringen, Jan Wouters, Marc Moonen
Characterization of cochlear implant artifacts in electrically evoked auditory steady-state responses doi:10.1016/j.bspc.2016.07.013
Received: 18 March 2016, Revised: 23 June 2016, Accepted: 26 July 2016, Available online: 1 August 2016
Copyright: The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
At contralateral recording electrodes, the artifact was shorter than the interpulse interval across subjects for 500 pps, which was not always the case for 900 pps.
The authors would like to thank all subjects who participated in the study. Furthermore, a special thanks goes out to Robert Luke and Tom Francart for their valuable feedback throughout the study. This research work was carried out in the frame of Research Project FWO nr. G.066213 ‘Objective mapping of cochlear implants’, IWT Project (IWT, 110722) ‘Signal processing and automatic fitting for next generation cochlear implants’ and KU Leuven Research Council CoE PFV/10/002 (OPTEC). The second author is supported with a Ph.D. grant by the Hermesfonds (141243). None of the authors have potential conflicts of interest to be disclosed.