Stream Segregation and Speech Recognition in Noise in Individuals With Cochlear Implants

Individuals with cochlear implants will complete tasks which measure auditory resolution, working memory, stream segregation, and speech recognition in the presence of competing speech using their everyday clinical device settings. The relationship between these tasks will be examined to identify the factors which predict successful speech recognition in the presence of competing speech.

Individuals with cochlear implants struggle to understand speech in the presence of competing talkers because they have trouble segregating auditory streams. The premise of this project is that individual differences in auditory resolution and cognitive ability across individuals with cochlear implants determine the extent to which they can segregate auditory streams from one another and hear out target speech embedded in competing talkers. Our goal is to test whether the link between speech recognition in noise and individual differences in auditory resolution and working memory in individuals with cochlear implants is due to the limitations that these individual differences place on stream segregation. The outcome measure to be predicted is sentence recognition in two-talker babble. Previous work has found that spectral and temporal modulation detection thresholds (measures of auditory resolution) and performance on the reading span task (a measure of working memory that is closely linked to fluid intelligence) are predictors of speech recognition in quiet. To account for these sources of variability in speech recognition, we will verify that these tasks jointly predict individual differences in sentence recognition in quiet. Adding competing talkers during the speech recognition task will introduce additional variability beyond the variability of speech recognition in quiet. We hypothesize that this additional variability with competing talkers should be predicted by individual differences in stream segregation ability, which will in turn be predicted by auditory resolution and working memory. Obligatory and voluntary stream segregation ability will be measured using rapidly presented digit sequences manipulated to have alternating fundamental frequencies (F0) for each digit. Participants will resist integration and repeat back only the digits presented with the higher F0. The magnitude of the F0 alternation will be manipulated to control the difficulty of segregating streams. The predicted relationship between stream segregation and sentence recognition will be tested for auditory resolution and working memory in independent and combined models. Completing this goal will identify the auditory and cognitive factors that support stream segregation in post-lingually deafened adults with cochlear implants. This identification will enable development of cochlear implant design and rehabilitation strategies to facilitate stream segregation in these patients as well as investigation of the developmental trajectories of these factors in children with cochlear implants. We plan to implement this study in at-home testing conditions to avoid risking coronavirus disease 2019 transmission in the lab, so this work will also determine the feasibility of at-home testing of individuals with cochlear implants. At-home testing would expand the amount and diversity of participants we are able to recruit for future studies.

Eligibility Criteria:
Inclusion Criteria:

* Has at least one cochlear implant.
* Lost their hearing during adulthood.
* Native English speaker.

Exclusion Criteria:

* Cognitive impairment