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Fourth International Symposium and Workshops: Objective Measures in Cochlear Implants

Medical University of Hannover

01.06. bis 04.06.2005, Hannover

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Automated pitch perception testing, averaged electrode voltage (AEV) measurements and artefact reduction using N.I.C.-libraries in Nucleus 24-channel CI systems

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  • corresponding author A. Beynon - Radboud University Nijmegen, ENT Dept., Nijmegen
  • T. Thielemans - Radboud University Nijmegen, ENT Dept., Nijmegen
  • C. Berenstein - Radboud University Nijmegen, ENT Dept., Nijmegen

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. Doc05omci010

The electronic version of this article is the complete one and can be found online at: http://www.egms.de/en/meetings/omci2005/05omci010.shtml

Published: May 31, 2005

© 2005 Beynon et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

Outline

Text

Introduction

Some test conditions ask for a direct stimulation of the cochlear implant in order to diminish possible disturbing external variables influencing the measurement outcomes. Direct stimulation of the implant should also improve the quality of the responses measured. For testing the integrity of an implant, averaged electrode voltages (AEVs) can be obtained through direct stimulation and recording of CI responses. The recording of these signals might be helpful to identify implant failures or inappropriate intracochlear current spread.

Materials and Methods

Previously, these measurements could be performed in 22-channel systems using MINT or custom-made programmes. Now, with the 24-channel system, it is possible to use a recently developed software library by Cochlear, containing many functions for the communication and stimulation with the Nucleus 24 implant system, i.e. NIC-libraries. E.g. with NICStream, it is even possible to online stream the speech processor with speech stimuli for electro-acoustical testing. Using the available NIC library functions, the user is now able to built a software application in which experiments can be performed that are not possible with standard clinical fitting software.

Results

In the present study, we have implemented three different software applications of using the libraries of NIC1.0 and NICStream to stimulate the cochlear implant:

1) To perform integrity measurements after implementing the NIC library in Labwindows CVI - an integrated C environment - a graphical user interface is developed for clinical application.

2) For more efficient assessment of tonotopy testing, an automated pitch estimation test is developed to obtain the behavioural responses to pitch perception of all electrodes.

3) To obtain artefact-free electrically evoked auditory cortical responses via direct stimulation of the electrodes using speech stimuli. First results show that it is possible to reduce the power up artefacts. However, amplitudes of stimulus-related artefacts have much higher amplitudes than power up artefacts, so that the reduction of only power up artefacts seem is obviously insufficient. A subtraction method is introduced to erase the artefacts.

Conclusions

Advantages and disadvantages of the NIC-libraries as a developmental tool for several experiments are addressed.