The Electrically Evoked Auditory Change Complex: Preliminary Results from Nucleus Cochlear Implant Users

Abstract

Objectives-The purpose of this study was to determine if changes in the position of the stimulating electrode in the cochlea could be used to elicit the electrically evoked auditory change complex (EACC) from Nucleus cochlear implant users.Design-Nine postlingually deafened adults participated in this study. Each study participant had been using his or her Nucleus CI24 cochlear implant for at least 3 months prior to testing. The speech processor was bypassed and the output of the implanted receiver/stimulator was controlled directly. The stimulus was a 600 ms burst of a biphasic pulse train (1000 pps). In control conditions, the stimulating electrode was held constant and stimulation continued throughout the 600 ms recording interval. In experimental conditions, the EACC was elicited by introducing a change in the stimulating electrode 300 ms after the onset of the pulse train. The EACC was recorded using surface electrodes. Three recordings of 100 sweeps each were obtained for each stimulus condition. Bandpass filtering (1 -100 Hz) was used to minimize contamination of the recordings by stimulus artifact. Averaged responses were then smoothed using a 40 ms wide boxcar filter and standard peak picking procedures were used to analyze these responses in the time domain.Results-In each case, a clear onset response (P1-N1-P2) was recorded. In the experimental conditions, a second evoked potential, the EACC, was also recorded following the change in stimulating electrode. This second response had general morphologic characteristics that were very similar to those of the onset response. Increasing the separation between the two stimulating electrodes in the experimental conditions resulted in a general trend toward increased EACC amplitudes.Conclusions-This report describes results of a set of experiments in which the speech processor of the cochlear implant was bypassed and the EACC was recorded in response to a change in stimulating electrode position. EACC amplitude was shown to increase as the separation between the two stimulating electrodes increased. While preliminary in nature, these results demonstrate the Correspondence: Carolyn J. Brown, PhD, 127B SHC, Dept. Speech Pathology and Audiology, University of Iowa, Iowa City, IA 52242, Phone: 319-335-8734, Fax: 319-335-8851, Email: carolyn-brown@uiowa.edu. Reprints: Use address listed above for correspondence Electrically evoked, auditory potentials were measured from Nucleus cochlear implant users. The speech processor was bypassed and the implanted electronics were controlled directly. A 600 ms train of biphasic current pulses was presented. In experimental conditions, the stimulus train included a change in the stimulating electrode position. The amplitude of the responses that were elicited by this change in electrode location tended to increase as the distance between the two stimulating electrodes increased. These results suggest that it may be feasible to use electrophysiologic techniques to assess sensitivity to change in various aspects of an ong...

Objective Measures of Electrode Discrimination With Electrically Evoked Auditory Change Complex and Speech-Perception Abilities in Children With Auditory Neuropathy Spectrum Disorder

“…Brown et al (2008) described the eACC in response to changes in stimulating electrode position recorded from implanted adult listeners using direct-in stimulation. In this study, the speech processor microphone was bypassed and the electrical biphasic pulse train delivered directly to a single electrode using proprietary software.…”

Acoustic Change Complex in Cochlear Implant Subjects in Comparison with Psychoacoustic Measures

“…Though the ACC was first described more than thirty years ago by Jerger, it came into the focus of attention, during the last years, for evaluating the discrimination capabilities in cochlear implant subjects (Friesen & Tremblay, 2006;Brown et al, 2008;Martin, 2007;Kim et al, 2009). It was shown that the ACC may be recorded in cochlear implant subjects with minimal artefacts due to the electrical stimulation (Martin, 2007).…”

“…Kim et al demonstrated that smallest level differences may evoke an EACC (Kim et al, 2009). Brown et al (2008) have shown, that the EACC can be elicited by an electrical stimulus switching from one electrode to another. They postulated that the EACC can be used as an objective index for spatial resolution in cochlear implant subjects.…”

A method for removing cochlear implant artifact

“…Cortical auditory evoked potentials (CAEPs) to sounds mediated through a cochlear implant have been used to assess both the developing auditory system (Eggermont et al, 1997;Gilley et al, 2008;Gordon et al, 2005;Ponton et al, 1999), and the effects of stimulation on the mature auditory system (Brown et al, 2008;Friesen and Tremblay, 2006;Groenen et al, 2001;Pantev et al, 2002;Ponton et al, 1993;Purdy et al, 2001).…”