When using a cochlear implant (CI) in one ear, children experience difficulties hearing speech in noise and localizing sounds in rooms. This is not surprising, as studies in normal hearing listeners have demonstrated that speech understanding in noise and sound localization can be very poor when binaural hearing is artificially disrupted. Inability to segregate speech from noise and to localize sounds can have a profound impact on the ability of a child to learn in environments such as classrooms, where it is typical to have multiple sounds arrive from various directions, and each child faces the challenge of segregating stimuli of interest from background noise. There has been a sweeping shift in clinical treatment, whereby bilateral CIs have become the standard of care, and 70% of bilateral CI users are children under 10 years of age. The vast majority of children perform significantly worse than their normal hearing, age-matched peers on sound localization and understanding of speech in noise. Using research processors that synchronize the CIs in the two ears, specific aims will investigate mechanisms of sound localization (Aim 1) and speech-in-noise segregation (Aim 2). In addition, we will evaluate whether peripheral measures of neural spread of excitation can serve as a useful tool for predicting binaural processing, in order to ultimately develop objective clinical tools for bilateral fitting of CIs (Aim 3). Studies will be done in implanted children who were congenitally deaf and implanted bilaterally during infancy and children born with hearing and acquired deafness during early childhood. In addition, children with normal hearing will be studied using binaural CI simulations, in order to understand the extent to which differences between CI user and normal hearing children are accounted for by signal degradation that is known to occur with CIs. Limits imposed by the CI simulations relative to standard acoustic cues will provide a benchmark for best performance levels to be expected from the CI populations. Ultimately, the work will lead to development of better speech processors for children who are deaf, and ideally better outcomes in their ability to hear speech in noise, localize sounds, and learn in complex noisy environments.
This research is aimed at advancing knowledge in auditory science, focusing on binaural hearing in deaf children who use bilateral cochlear implants. We aim to better understand what conditions are likely to maximize the success of children who use bilateral cochlear implants. Findings will have a direct translational component, with regard to bilateral fitting choices, rehabilitation and counseling. There will be direct relevance to childre who are deaf, because parents often struggle with the decision regarding bilateral implantation vs. saving an ear for future technology. If bilateral CIs can ultimately provide excellent binaurl hearing, and if alternative treatments for deafness are not feasible, our work will be of importance to pediatric decision-making.
|Kan, Alan; Litovsky, Ruth Y (2015) Binaural hearing with electrical stimulation. Hear Res 322:127-37|
|Hess, Christi; Zettler-Greeley, Cynthia; Godar, Shelly P et al. (2014) The effect of differential listening experience on the development of expressive and receptive language in children with bilateral cochlear implants. Ear Hear 35:387-95|
|Tolnai, Sandra; Litovsky, Ruth Y; King, Andrew J (2014) The precedence effect and its buildup and breakdown in ferrets and humans. J Acoust Soc Am 135:1406-18|
|Litovsky, Ruth Y; Ehlers, Erica; Hess, Christi et al. (2013) Reaching for sound measures: an ecologically valid estimate of spatial hearing in 2- to 3-year-old children with bilateral cochlear implants. Otol Neurotol 34:429-35|
|Grieco-Calub, Tina M; Litovsky, Ruth Y (2012) Spatial acuity in 2-to-3-year-old children with normal acoustic hearing, unilateral cochlear implants, and bilateral cochlear implants. Ear Hear 33:561-72|
|Litovsky, Ruth Y (2011) Review of recent work on spatial hearing skills in children with bilateral cochlear implants. Cochlear Implants Int 12 Suppl 1:S30-4|
|Todd, Ann E; Edwards, Jan R; Litovsky, Ruth Y (2011) Production of contrast between sibilant fricatives by children with cochlear implants. J Acoust Soc Am 130:3969-79|
|Litovsky, Ruth Y; Godar, Shelly P (2010) Difference in precedence effect between children and adults signifies development of sound localization abilities in complex listening tasks. J Acoust Soc Am 128:1979-91|
|Grieco-Calub, Tina M; Litovsky, Ruth Y (2010) Sound localization skills in children who use bilateral cochlear implants and in children with normal acoustic hearing. Ear Hear 31:645-56|
|Godar, Shelly P; Litovsky, Ruth Y (2010) Experience with bilateral cochlear implants improves sound localization acuity in children. Otol Neurotol 31:1287-92|
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