Mathew, Rajeev;
(2019)
Development and significance of the spatial auditory change complex in adult cochlear implant users.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Despite their great success, cochlear implants (CIs) are associated with a wide range in speech perception outcomes. Interactions of electrode contacts on the CI array, resulting in impaired transmission of the auditory signal, may contribute to poor outcome in certain individuals. The aim of this thesis was to determine whether the spatial auditory change complex (ACC), an electrophysiological measure of electrode discrimination, could be used to objectively assess electrode independence, with a view to using this as a clinical tool for patient assessment. In a series of experiments, the spatial ACC and behavioural electrode discrimination were measured in adult CI users. It was found that it is feasible to measure the spatial ACC in CI devices from different manufacturers and during the early period after switch-on. There was a strong relationship between objective and behavioural measures of electrode discrimination and in several cases, the development of the spatial ACC preceded accurate behavioural discrimination. Longitudinal measurements revealed that the amplitude of the spatial ACC and behavioural discrimination scores increased significantly over the first 6 to 12 months of CI use, providing evidence for auditory plasticity. The time course of adaptation varied substantially, and was slower and more limited in certain individuals. Speech perception was found to be more consistently related to behavioural measures of electrode discrimination than to the spatial ACC. Increasing stimulus intensity led to a significant increase in the spatial ACC amplitude and behavioural discrimination scores. By altering the recording setup and stimulus characteristics, the efficiency and sensitivity of spatial ACC measurements could be improved. These findings show that the spatial ACC provides a useful measure of electrode independence. It is proposed that these measurements could be used to guide clinical interventions that lead to improved hearing outcome in CI users.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Development and significance of the spatial auditory change complex in adult cochlear implant users |
| Event: | UCL (University College London) |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Licence (https://creativecommons.org/licenses/by-nc-nd/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. Third party copyright material has been removed from ethesis. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10064942 |
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