gms | German Medical Science

Fourth International Symposium and Workshops: Objective Measures in Cochlear Implants

Medical University of Hannover

01.06. bis 04.06.2005, Hannover

Artefact reduction in Neural Response Imaging via a modified stimulation signal

Meeting Abstract

  • corresponding author C. Frohne-Büchner - Medizinische Hochschule Hannover, Hannover
  • M. Brendel - Medizinische Hochschule Hannover, Hannover
  • A. Büchner - Medizinische Hochschule Hannover, Hannover
  • L. Litvak - Advanced Bionics Corporation, Valencia
  • G. Emadi - Advanced Bionics Corporation, Valencia
  • H. Alabashyan - Advanced Bionics Corporation, Valencia
  • R.D. Battmer - Medizinische Hochschule Hannover, Hannover
  • T. Lenarz - Medizinische Hochschule Hannover, Hannover

Medical University of Hannover, Department of Otolaryngology. Fourth International Symposium and Workshops: Objective Measures in Cochlear Implants. Hannover, 01.-04.06.2005. Düsseldorf, Köln: German Medical Science; 2005. Doc05omci048

The electronic version of this article is the complete one and can be found online at:

Published: May 31, 2005

© 2005 Frohne-Büchner et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



All modern cochlear implant systems allow to record the response of the auditory nerve. This technique is currently a part of the clinical routine. However, the proper method of artefact reduction is still under discussion. After the electrical stimulus some residual charge remains on the contacts and in the tissue close to the contacts that drives the amplifier into saturation. In addition, residual charge decays with a similar time scale as neural response waveforms, resulting in artefact that can distort the measured neural signal. Schlösser, Zierhofer and Hochmair [1] showed that it is possible to reduce the residual charge by introducing a third phase to the stimulus. The artefact could be significantly reduced. The research software "Bionic Ear Data Collection System" for the Advanced Bionics implants CII and HiRes90K allows to record the neural response imaging (NRI) with flexible stimulation patterns. It was used within a study to compare artefact reduction via alternating stimulus polarity with reduction via a third phase in a group of 10 post-lingual deaf adults. Responses were recorded at sub-threshold and supra-threshold levels as a function of amplitude of the third phase relative to the two initial phases. We also assessed whether loudness evoked by triphasic pulses was similar to that evoked by biphasic pulses of similar amplitude for the first two phases by performing a loudness-balancing task between the two stimuli. Preliminary data indicate that optimal third phase reduces the stimulus artifact. Thus, the first negative peak, N1, is less distorted and latency as well as amplitude can be defined more reliably.


Schlösser H, Ziehofer CM, Hochmair ES. Measuring electrically evoked compound action potentials using triphasic pulses for the reduction of the residual stimulation artifact; presented as a poster during the "Conference on Implantable Auditory Protheses", Asilomar, August, 19th-24th, 2001