Biomedical Engineering Reference
In-Depth Information
Development of a Model of the Electrically
Stimulated Cochlea
Waldo Nogueira, Waldemar Würfel, Richard T. Penninger and
Andreas Büchner
Abstract
Cochlear Implants (CIs) are implantable medical devices that can restore
the sense of hearing in people with profound sensorineural hearing loss. Clinical trials
assessing speech intelligibility in CI users have found large inter subject variability.
One possibility to explain the variability are the individual differences in the interface
created between electrodes and the auditory nerve. For example, the exact position
of the electrodes in each cochlea may differ from one patient to another. Additionally
the amount of functional auditory neurons might also vary considerably between CI
users. In order to understand the variability, models of the voltage distribution of the
electrically stimulated cochlea may be useful. With this purpose we have developed
a model that allows to simulate the voltage distribution at different positions on
the auditory nerve. Simulations show differences in the extracellular voltage of the
spiral ganglions depending on the electrode positions and the cochlear size, which
might explain some of the variability. Finally, the model of the electrically stimulated
cochlea has been used to simulate the extracellular voltage patterns produced by
different instrumental sounds. These patterns have been inserted in an automatic
instrument classifier that helps to illustrate the mentioned variability.
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Keywords
Cochlear implant
Finite element method
Electric field
Cochlea
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Sound coding strategy
Instrument identification
1 Introduction
Cochlear implants (CIs) are medical implantable devices that are used to restore the
sense of hearing for people with profound sensorineural hearing loss given that the
auditory anatomy is fully developed [
21
]. Cochlear implantation (and subsequent
rehabilitation) typically allows even children with prelingual deafness to develop
spoken language understanding and production [
4
,
15
]. In CIs the auditory nerves are
