The goal of our research is to understand the effects of asymmetric hearing loss in adults and children. Hearing asymmetry occurs, for example, when one ear has profound hearing loss and the other ear has normal hearing. Or, when one ear is profoundly deaf but the better ear has partial hearing. In either case, the imbalanced inputs detrimentally affect communication in everyday life and have other negative consequences.
In Aim 1, we identify the sources of variability contributing to outcomes observed in adults and children with unilateral hearing loss. Understanding this variability could improve counseling and treatment options for patients. We will evaluate factors that predict speech recognition in noise and localization by investigating cognitive abilities, associated demographics, and measures of performance.
In Aim 2, we assess the hypothesis that deficits in comprehending speech in noise with unilateral hearing loss affect processing in non- auditory cognitive brain regions. We propose a functional imaging study of activity evoked by high and low predictability sentences in the presence and absence of multi-talker babble. We predict that compensating for degraded speech comprehension in noise involves greater activation of cognitive centers in temporo-parietal, inferior and dorsolateral frontal, and cingulate cortex in adults with unilateral hearing loss compared to those with normal hearing.
In Aim 3, we examine the benefit of cochlear implantation for adults and children with asymmetric hearing loss and varied ages at onset of deafness and hearing histories in the poorer ear. We predict that even if one ear has partial hearing and the brain has learned to hear with a fairly good acoustic signal, age at onset of deafness in the poorer ear will be associated with outcome.
In Aim 4, we identify factors in bilateral cochlear implant recipients that contribute to asymmetry in speech recognition between ears and reduced bilateral performance. In prelingually deaf children, we expect that a longer time between surgeries corresponds to larger asymmetries in speech recognition between ears and reduced bilateral performance. In postlingual adults, we predict that greater divergence in electrode placement between cochleas correlates with larger asymmetries in speech recognition between ears, reduced bilateral performance, and larger interaural differences in pitch percepts. To summarize, the proposed research program will probe the basis of behavioral variability and brain reorganization in unilateral hearing loss. Findings will determine how asymmetry in hearing affects behavioral outcomes and whether new considerations exist for early onset of unilateral deafness. Knowledge gained could influence decisions about treated ear, treatment types, and timing of treatment in children and adults with asymmetric hearing loss. Finally, results will enhance understanding of inter-cochlea electrode placement effects and potentially influence treatment decisions for bilateral implant recipients.

Public Health Relevance

Asymmetric hearing loss results in everyday communication difficulties for adults and children. Knowledge gained from the proposed studies could influence decisions about treatment types and timing of treatments in individuals with asymmetric hearing loss. Finally, results will enhance understanding of cochlear electrode placement effects and potentially influence treatment decisions for bilateral cochlear implant recipients.

National Institute of Health (NIH)
Research Project (R01)
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Auditory System Study Section (AUD)
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Donahue, Amy
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Washington University
Schools of Medicine
Saint Louis
United States
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Firszt, Jill B; Reeder, Ruth M; Dwyer, Noël Y et al. (2015) Localization training results in individuals with unilateral severe to profound hearing loss. Hear Res 319:48-55
Reeder, Ruth M; Firszt, Jill B; Holden, Laura K et al. (2014) A longitudinal study in adults with sequential bilateral cochlear implants: time course for individual ear and bilateral performance. J Speech Lang Hear Res 57:1108-26
Dwyer, Noel Y; Firszt, Jill B; Reeder, Ruth M (2014) Effects of unilateral input and mode of hearing in the better ear: self-reported performance using the speech, spatial and qualities of hearing scale. Ear Hear 35:126-36
Long, Christopher J; Holden, Timothy A; McClelland, Gary H et al. (2014) Examining the electro-neural interface of cochlear implant users using psychophysics, CT scans, and speech understanding. J Assoc Res Otolaryngol 15:293-304
Burton, Harold; Firszt, Jill B; Holden, Timothy (2013) Hearing thresholds and FMRI of auditory cortex following eighth cranial nerve surgery. Otolaryngol Head Neck Surg 149:492-9
Holden, Laura K; Finley, Charles C; Firszt, Jill B et al. (2013) Factors affecting open-set word recognition in adults with cochlear implants. Ear Hear 34:342-60
Cadieux, Jamie H; Firszt, Jill B; Reeder, Ruth M (2013) Cochlear implantation in nontraditional candidates: preliminary results in adolescents with asymmetric hearing loss. Otol Neurotol 34:408-15
Holden, Laura K; Brenner, Christine; Reeder, Ruth M et al. (2013) Postlingual adult performance in noise with HiRes 120 and ClearVoice Low, Medium, and High. Cochlear Implants Int 14:276-86
Burton, Harold; Firszt, Jill B; Holden, Timothy et al. (2012) Activation lateralization in human core, belt, and parabelt auditory fields with unilateral deafness compared to normal hearing. Brain Res 1454:33-47
King, Sarah E; Firszt, Jill B; Reeder, Ruth M et al. (2012) Evaluation of TIMIT sentence list equivalency with adult cochlear implant recipients. J Am Acad Audiol 23:313-31

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