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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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The Sound of Music – Two Novel EEG-Paradigms for Measuring Discrimination of Music in Cochlear Implant Users Bjørn Petersen a*, Anne Sofie Friis Andersen a*, Niels Trusbak Haumann a, Martin Dietz b, Andreas Højlund b, Elvira Brattico a, Franck Michel c, Søren Kamaric Riis d, Peter Vuust a a) Center for Music in the Brain, dpt. of Clinical Medicine, Aarhus University & The Royal Academy of Music Aarhus/Aalborg. b) Center for Functionally Integrative Neuroscience. c) Clinic of Audiology, Aarhus University Hospital, d) Oticon Medical *shared first authorship 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.   Introduction Music listening with a cochlear implant (CI) is challenging due to the poor representation of fine structure information. Therefore, extensive research has been initiated in the quest for improved music perception with a CI. Typically, musical skills are measured by behavioural methods. However, to provide objective measurements and an understanding of the cortical changes which underlie the auditory progress, neuroimaging methods are in demand. EEG is a non-invasive, silent and objective method which enables recording of event-related brain potentials (ERPs) and offers the opportunity to investigate the neural basis of perception with a high temporal resolution. The current study was initiated with two goals. In the first step, the goal is to develop and validate two novel musical EEG paradigms to be used in future CI research. 1) A multifeature MMN paradigm, presenting four deviants (pitch, intensity, timbre and rhythm) at four levels of magnitude in a no-standards configuration, and 2) a naturalistic paradigm presenting three ecological musical pieces. In a parallel step, we aim to examine the effect of a novel sound compression strategy (VoiceGuard) developed by OM. Compared to the typical automatic gain control, VoiceGuard leaves room for a wider dynamic range, which could prove beneficial for the music perception of CI users. As data collection from CI users has not been concluded at the time of submission, results from normal-hearing (NH) participants are reported. Methods/Results Two groups of NH participants were included and subjected to the tests: a group of young adults (N: 17, mean age 25) and a group of older adults (N: 14, mean age 63). The MMN paradigm elicited significant MMN responses for all deviants in both groups. Furthermore, MMN amplitude strengths were in accordance with the levels of deviance. Results from a supplementary behavioural measurement confirmed the overall findings of the MMN measurements. The naturalistic paradigm elicited significant P2 responses for the musical features spectral flux, brightness, roughness and RMS. Conclusion The NH results suggest encouraging potential for using the paradigm in future CI research. As a preliminary finding, we have been able to show significant MMN responses in single subject analyses. With clinical application in mind, this is important since it suggests potential use of the MMN paradigm for objective prognostication and assessment of CI functioning in individual CI patients. The study is work in progress and so far, data from eight experienced and eight newly operated CI users have been collected. We expect preliminary results from these groups to be available for presentation at the conference.
Original languageEnglish
Publication year11 Jul 2019
Publication statusPublished - 11 Jul 2019
EventCI2019 Pediatric: 16th Symposium on Cochlear Implants in Children: CI 2019 - Hollywood, Florida, Hollywood, FL, United States
Duration: 10 Jul 201913 Jul 2019

Conference

ConferenceCI2019 Pediatric: 16th Symposium on Cochlear Implants in Children
LocationHollywood, Florida
CountryUnited States
CityHollywood, FL
Period10/07/201913/07/2019

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