Neurophysiological Differences in Emotional Processing by Cochlear Implant Users, Extending Beyond the Realm of Speech

Objective: Cochlear implants (CIs) restore a sense of hearing in deaf individuals. However, they do not transmit the acoustic signal with sufficient fidelity, leading to difficulties in recognizing emotions in voice and in music. The study aimed to explore the neurophysiological bases of these limitations. Design: Twenty-two adults (18 to 70 years old) with CIs and 22 age-matched controls with normal hearing participated. Event-related potentials (ERPs) were recorded in response to emotional bursts (happy, sad, or neutral) produced in each modality (voice or music) that were for the most part correctly identified behaviorally. Results: Compared to controls, the N1 and P2 components were attenuated and prolonged in CI users. To a smaller degree, N1 and P2 were also attenuated and prolonged in music compared to voice, in both populations. The N1–P2 complex was emotion-dependent (e.g., reduced and prolonged response to sadness), but this was also true in both populations. In contrast, the later portion of the response, between 600 and 850 ms, differentiated happy and sad from neutral stimuli in normal hearing but not in CI listeners. Conclusions: The early portion of the ERP waveform reflected primarily the general reduction in sensory encoding by CI users (largely due to CI processing itself), whereas altered emotional processing (by CI users) could be found in the later portion of the ERP and extended beyond the realm of speech. ACKNOWLEDGMENTS: We thank Duha Ahmed, Frederik Desaulniers, Simon Rigoulot, and Isabelle Peretz for their help. M.D. designed the experiments, collected the data, analyzed the data, and wrote up the article. M.F. helped with EEG recording. S.P. helped develop the rationale and with the selection of the MAV and MEB stimuli. A.Z. worked on the conceptualization of the research program. A.L. developed the rationale, worked with MD on experimental design, and contributed to article writing. This study was supported by a grant from the Grammy Foundation (to A.L.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the article. We are grateful to all the participants for their time and effort, as well as the Institut Raymond-Dewar and the MAB-Mackay center for their help in recruiting CI users. The authors have no conflicts of interest to disclose. Received August 9, 2018; accepted December 12, 2018. Address for correspondence: Mickael L. D. Deroche, Department of Otolaryngology–Head and Neck Surgery, McGill University, 1001 Decarie Blvd, Montreal, H3G 2A8, Canada. E-mail: mickael.deroche@mcgill.ca Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

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