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BioMed Research International
Volume 2015, Article ID 394687, 10 pages
http://dx.doi.org/10.1155/2015/394687
Research Article

Modeling of Auditory Neuron Response Thresholds with Cochlear Implants

1ENT Department and University Montpellier 1, University Hospital Gui de Chauliac, 34295 Montpellier, France
2Audiology Department I-PAudioM, INSERM U1051 Unit, Institute for Neurosciences of Montpellier, 34081 Montpellier, France
3Department of Medical Information and Biostatistics, University Hospital of Montpellier, Montpellier, France
4U 1061, CIC 1001, INSERM, 34295 Montpellier, France
5Neuroradiology Department, University Hospital Gui de Chauliac, 34295 Montpellier, France
6Audiophonology and Speech Disorders Department, Institute Saint Pierre, 34250 Palavas, France

Received 14 November 2014; Accepted 21 January 2015

Academic Editor: Chung-Feng Hwang

Copyright © 2015 Frederic Venail et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The quality of the prosthetic-neural interface is a critical point for cochlear implant efficiency. It depends not only on technical and anatomical factors such as electrode position into the cochlea (depth and scalar placement), electrode impedance, and distance between the electrode and the stimulated auditory neurons, but also on the number of functional auditory neurons. The efficiency of electrical stimulation can be assessed by the measurement of e-CAP in cochlear implant users. In the present study, we modeled the activation of auditory neurons in cochlear implant recipients (nucleus device). The electrical response, measured using auto-NRT (neural responses telemetry) algorithm, has been analyzed using multivariate regression with cubic splines in order to take into account the variations of insertion depth of electrodes amongst subjects as well as the other technical and anatomical factors listed above. NRT thresholds depend on the electrode squared impedance (β = −0.11 ± 0.02, ), the scalar placement of the electrodes (β = −8.50 ± 1.97, ), and the depth of insertion calculated as the characteristic frequency of auditory neurons (CNF). Distribution of NRT residues according to CNF could provide a proxy of auditory neurons functioning in implanted cochleas.