The Role of Early Intact Auditory Experience on the Perception of Spoken Emotions, Comparing Prelingual to Postlingual Cochlear Implant Users

Abstract

Objectives: Cochlear implants (CI) are remarkably effective, but have limitations regarding the transformation of the spectro-temporal fine structures of speech. This may impair processing of spoken emotions, which involves the identification and integration of semantic and prosodic cues. Our previous study found spoken-emotions-processing differences between CI users with postlingual deafness (postlingual CI) and normal hearing (NH) matched controls (age range, 19 to 65 years). Postlingual CI users over-relied on semantic information in incongruent trials (prosody and semantics present different emotions), but rated congruent trials (same emotion) similarly to controls. Postlingual CI’s intact early auditory experience may explain this pattern of results. The present study examined whether CI users without intact early auditory experience (prelingual CI) would generally perform worse on spoken emotion processing than NH and postlingual CI users, and whether CI use would affect prosodic processing in both CI groups. First, we compared prelingual CI users with their NH controls. Second, we compared the results of the present study to our previous study (Taitlebaum-Swead et al. 2022; postlingual CI). Design: Fifteen prelingual CI users and 15 NH controls (age range, 18 to 31 years) listened to spoken sentences composed of different combinations (congruent and incongruent) of three discrete emotions (anger, happiness, sadness) and neutrality (performance baseline), presented in prosodic and semantic channels (Test for Rating of Emotions in Speech paradigm). Listeners were asked to rate (six-point scale) the extent to which each of the predefined emotions was conveyed by the sentence as a whole (integration of prosody and semantics), or to focus only on one channel (rating the target emotion [RTE]) and ignore the other (selective attention). In addition, all participants performed standard tests of speech perception. Performance on the Test for Rating of Emotions in Speech was compared with the previous study (postlingual CI). Results: When asked to focus on one channel, semantics or prosody, both CI groups showed a decrease in prosodic RTE (compared with controls), but only the prelingual CI group showed a decrease in semantic RTE. When the task called for channel integration, both groups of CI users used semantic emotional information to a greater extent than their NH controls. Both groups of CI users rated sentences that did not present the target emotion higher than their NH controls, indicating some degree of confusion. However, only the prelingual CI group rated congruent sentences lower than their NH controls, suggesting reduced accumulation of information across channels. For prelingual CI users, individual differences in identification of monosyllabic words were significantly related to semantic identification and semantic-prosodic integration. Conclusions: Taken together with our previous study, we found that the degradation of acoustic information by the CI impairs the processing of prosodic emotions, in both CI user groups. This distortion appears to lead CI users to over-rely on the semantic information when asked to integrate across channels. Early intact auditory exposure among CI users was found to be necessary for the effective identification of semantic emotions, as well as the accumulation of emotional information across the two channels. Results suggest that interventions for spoken-emotion processing should not ignore the onset of hearing loss.