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Peter Vuust

The Sound of Music: Two Novel EEG-Paradigms for Measuring Discrimination of Music in Cochlear Implant Users

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Introduction
Music listening with a cochlear implant is challenging due to the lack of temporal fine structure and a limited dynamic range in the CI signal. Hence, a number of ongoing efforts aim to improve music perception with a CI. For this purpose, objective and feasible music tests are in demand. Thus, the aim of this study is to design and validate two novel musical EEG-paradigms for use in future CI research.
In a wider perspective, the study aims to investigate whether a novel sound processing strategy implementing output compression may be beneficial for music listening with a CI, as compared to front-end automatic gain control strategies.

Methods
EEG paradigms
1. The CI Musical Multifeature Mismatch negativity (MMN) -paradigm integrates a new approach in which no standard stimuli are presented. Deviants in pitch, timbre, intensity and rhythm are embedded in an Alberti bass pattern and presented randomly at four levels of magnitude.
2. The Free-listening paradigm uses the Music Information Retrieval toolbox. Hereby, it is possible to investigate the relation between musical features and ERP responses. Here, participants listened to an excerpt of the tango piece Adios Noñino.
Neither of the two approaches have previously been tested on CI-users.

Participants. Eleven experienced CI-users and 14 normal hearing controls underwent EEG-recording while listening to the paradigms in two different sessions. In addition, they completed a behavioural test for discrimination of the music features and levels also presented in the MMN-paradigm.

Results
The CI paradigm elicited significant responses to all deviants in both experimental groups, across levels. This indicates both the paradigm’s potential to measure CI-users’ discrimination of details in music and the success of the CI in transmitting them. However, overall MMN responses of CI-users were significantly smaller compared to NH listeners.

While NH listeners showed MMN responses that were in accordance with the deviation level magnitude, CI users’ MMN amplitudes were less consistent with level hierarchy, mainly driven by undifferentiated responses to the levels of change in pitch.

In the behavioral test, CI-users scored above chance, but significantly below the NH group in discrimination of all deviants, except rhythm. Hit rates corresponded well with levels of magnitude.

Free-listening paradigm analyses showed significant N1 og P2 ERPs to increases in spectral flux and loudness in NH controls, but not in CI-users. For spectral flux, however, the N1 response of CI-users was not significantly smaller than that of NH, suggesting basic detection of changes in timbral features of “real music”. The lack of a significant response to increases in loudness may be explained by the strongly reduced dynamic range of the CI sound transmission.

Conclusion
These results are encouraging indications of the potential of the two novel EEG-paradigms as tools for objective measurements of music discrimination. Despite high complexity, the CI Mumufe MMN paradigm is both accurate and feasible and may provide strong evidence of CI users’ musical discrimination abilities and thresholds. Free-listening paradigm results suggest that inferences of CI-users’ music perception are possible under conditions that are comparable to their everyday music experience. However, more participants and more analyses are needed to make firm conclusions.
Original languageEnglish
Publication year16 Jul 2019
Publication statusPublished - 16 Jul 2019
Event2019 Conference on Implantable Auditory Prostheses (CIAP): CIAP - Granlibakken Conference Center, Lake Tahoe, United States
Duration: 14 Jul 201919 Jul 2019
http://www.ciaphome.org/

Conference

Conference2019 Conference on Implantable Auditory Prostheses (CIAP)
LocationGranlibakken Conference Center
CountryUnited States
CityLake Tahoe
Period14/07/201919/07/2019
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