This application requests continuation of the Iowa Cochlear Implant Clinical Research Center. Hearing preservation and combining acoustic plus electric speech processing have become very important concepts and our Center has played an important role in identifying the significance of residual acoustic hearing. We believe that hearing-preservation electrodes will improve outcomes because they allow users to combine electric auditory stimulation with any residual natural acoustic hearing. Our overarching goal is to examine how this hybrid approach to speech processing might benefit new populations of adults and children. We will also investigate the use of these less invasive electrodes in profoundly deaf infants, where they might help preserve the structural elements of the organ of Corti and enable this population to take advantage of ongoing future research to regenerate the peripheral auditory system. Our first objective aims to compare how electrode length affects the patient's ability to adapt to hearing the severely distorted frequency-place maps produced when acoustic plus electric stimulation are combined. This assessment will examine outcomes for hearing, speech and language, and music perception and enjoyment, and will also characterize Cl users in terms of underlying processing mechanisms. Thus, we propose to study the plasticity, learning, and adaptation mechanisms that might be central to predicting good outcomes. Our second objective is to define the boundaries between the appropriateness of hearing aids versus cochlear implants in populations of hard of hearing children. Third, we will examine whether profoundly deaf infants develop speech perception and language equally well with standard-length cochlear implants versus less invasive electrodes. We will study hearing-preservation electrode CIs in 105 adults and 80 children with residual acoustic hearing and 20 profoundly deaf infants. Control subjects will be obtained from a research registry that now has enrolled 335 previously implanted adults and children. Five research projects, an administrative Core A, and Patient Care, Speech Processing, and Technical Core B will address the above goals. The five research projects are highly integrated and depend on data from each other to answer the experimental questions.
This research has the potential to alter clinical practice. Selection of less invasive CIs will improve the ability to hear in challenging listening environments, such as competing noise and music, for severely hearing impaired populations. It might also provide an opportunity for profoundly deaf infants to take advantage of future regenerative research. Subproject 1 Acoustic Plus Electric Hearing Principal Investigator: Christopher W. Turner, Ph.D. DESCRIPTION (provided by applicant): Preservation of residual acoustic hearing during cochlear implantation has become an important improvement in the performance of cochlear implants. Not only does it improve the performance of implants (particularly for noisy, real-world listening conditions) but also allows the treatment of patients with severe high-frequency hearing loss, who have substantial low-frequency hearing. This project proposes to continue this work on combining acoustic plus electric (A+E) hearing. In addition to the overall goal of improving patient care for hearing loss, several unique research opportunities arise from this work. The first opportunity arises because of the new population of patients that will be implanted with these A+E devices. Never before have patients with such high levels of pre-operative residual hearing been implanted in such a large-scale project. We are at the same time seeing levels of performance for the transmission of speech through the short electrode that are surprising in light of the previous literature. This will allow us to re-examine some of the commonly held beliefs about the limitations of electric stimulation due to channel interaction. The second opportunity arises because the short-electrode Hybrid implant assigns low- and mid-frequency speech bands to extreme basal locations in the cochlea. Thus we have a unique opportunity to study the effects of remapping, neural plasticity, and adaptation to highly-distorted place-frequency maps in the cochlea.
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