AA2 Coch Implants
AA2 Objective Assessment of Cochlear Implants with a computer program
Responsible: Willy Serniclaes
Members: Cédric Gendrot, Jacqueline Vaissière, Stéphanie Borel & Clara Legendre
Description
A central question of Axe 4 is to understand how language-specific mechanisms are acquired during perceptual development. In the case of deaf children with Cochlear Implant (CI children), possible constraints in the development of speech perception arise either from auditory deprivation during the first months of life or to technological limitations in the transmission of acoustic signals by the implant devices. Previous research made it fairly clear that relatively short periods of auditory deprivation (up to some 2-3 years of age) do not modify the architecture of speech perception. The perception of speech sounds by CI children is not qualitatively different from the one of normal-hearing control children (NH children). CI children exhibit he same degree of “Categorical Perception” than NH children, i.e. the relationship between the discrimination and identification performances does not depend on the group (Medina & Serniclaes, 2009, Rev. Log. Fon. Audiol.; Bouton et al., 2012, J.Speech Lang. Hrng. Res.). CI children also exhibit he same degree of “Lexicality Effect” than NH children, i.e. both are equally better at discriminating words compared to pseudowords (Bouton et al., 2011, Speech Com.). However, there are quantitative differences between CI and NH children. CI children exhibit a deficit in accuracy in the perception of phonological features and this deficit is most pronounced for the nasality feature compared to the other consonant or vowel features (mode and place of articulation, voicing & aperture: Bouton et al., 2011; 2012). These differences in precision are seemingly due to the acoustic limitations of the cochlear implant in the coding of spectral cues. The aim of the present work package is to specify the origin of these acoustic limitations. The method for assessing the CI performances will be based on a computer simulation of speech perception. The output signals of the CI, which are normally send to the auditory nerve, will be transferred on a micro-computer and classified into phonemes with computer software (Serniclaes et al., 1996, Audiology; 1998, Acustica). The classification performances will be tested with large speech databases thereby ensuring their reliability. With this method the computer will be used as a virtual CI user which offers the possibility of assessing the multiple possible combinations of the implant control parameters (i.e. the “tuning strategy”) without mobilizing the real users and the paramedical staff. Preliminary research has demonstrated the faisability of this method and its validity (Serniclaes, 2001, ISWOMCI). The effects of a change in tuning strategy on speech perception for different electrophysiological profiles, corresponding to different CI users, were correlated to the effects obtained with computer simulations. Possible applications of this objective method are: (1) to obtain the best CI tuning for a given patient by simulating his/her individual electrophysiological profile (i.e. number of active CI channels and bandwidths); (2) compare the performances of different CI prototypes. We already have started with preliminary investigations of the acoustic cues involved in the perception of the nasality feature by CI and NH participants, as this feature is the most problematic for CI users. These behavioral investigations will be followed by comparisons with computer assessments and electrophysiological assessments (auditory brainstem potentials). Further investigations will be aimed at explaining the differences in perceptual acuity between nasality and other phonological features.
Links
Hung Thai-Van, Evelyne Veuillet, Ludovic Bellier & Anne Caclin. Service d'Audiologie & d'Explorations Orofaciales Hôpital Edouard Herriot - Hôpital Femme Mère Enfant - Hôpital Lyon Sud
Centre de Recherche en Neurosciences de Lyon
Marie-Thèrése Lenormand, Institut de Psychologie, Université Paris-Descartes
http://recherche.parisdescartes.fr/LPPS/Membres/Membres-titulaires/Marie-Therese-Le-Normand
