Stream Segregation and Speech Recognition in Noise in Individuals With Cochlear Implants
Condition: Cochlear Implants
Study type: Observational

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): Cochlear Implants
Intervention type(s): Device
Intervention description(s): Individuals with cochlear implants will be tested on their hearing ability. Auditory recordings of speech will be played to participants from a loudspeaker. Recordings will be edited to add competing noise sources and to adjust talker voice pitch. Synthetic sounds will be manipulated to control auditory cue salience in detection tasks.
Observational model: Case-Only
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Individuals with Cochlear Implants who are enrolled in the Boys Town National Research
        Hospital research database