2015 |
Ortmann, Amanda Judith |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
Aging and Cochlear Nonlinearity @ University of Southern California
? DESCRIPTION (provided by applicant): The long-term objectives of this project are to examine the changes in cochlear nonlinearity in aging individuals and relate these changes to auditory perception. Specifically, the aims of the project seek to (1) determine whether aging produces a more linear cochlear response as measured by otoacoustic emissions (OAE) and (2) determine the effect of age on perceptual loudness growth and relate these measures to distortion product otoacoustic emissions (DPOAE). Past work has established that aging has a greater effect on the nonlinear distortion emissions (DPOAE) than other emissions that do not require cochlear nonlinearity, such as the linear reflection-type emissions. In a healthy cochlea, the DPOAE grows in a near-linear fashion as a function of level for low-level signals, then growth becomes compressive at moderate intensities. DPOAE input/output (I/O) functions provide a remote estimate of the compressive characteristics of the cochlea. In addition, there is evidence that the perception of loudness, while having central factors, is related peripherally to the mechanical nonlinearities of the cochlea. The experiments outlined in this project will allow for the comparison of the DPOAE level-dependent growth, the magnitudes of the different emission types, as well as perceptual loudness growth across three different age groups (young-, middle-, and older-aged). The first aim of determining whether the cochlea generates a more linear response with age will be addressed by (a) measuring the DPOAE as a function of level to provide an index of cochlear compression and (b) comparing the magnitude of the distortion emissions, which are indicators of cochlear nonlinearity, versus reflection emissions (stimulus frequency OAEs), which are generated by a linear process. For aim 1a, the linear and compressive features of the DPOAE input/output functions of young, healthy ears as well as of aging ears with and without hearing loss will be examined to investigate whether the cochlea becomes more linear as it ages, independent of hearing loss. Aim 1b seeks to measure whether aging preferentially reduces the magnitude of the nonlinear distortion emission relative to the linear reflection emission. The second aim, involving examination of the effect of aging on perceptual loudness growth, will be accomplished by conducting a measure of categorical loudness scaling with all the participants and comparing the results across the three different age groups. Furthermore, this experiment will examine the relationship between changes in the perception of loudness and the physiological changes measured in aim 1a to determine whether the physiologic changes in cochlear nonlinearity can account for changes in the perception of loudness. This work is relevant to hearing health field because it will provide information regarding the changes in the aging auditory peripheral system. By understanding age-related changes in cochlear function and its impact on auditory perception, intervention and remediation may be more targeted and effective.
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0.955 |
2021 |
Adunka, Oliver Franz Ortmann, Amanda Judith |
U01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Clinical Utility of Residual Hearing in the Cochlear Implant Ear
Abstract A major concern in cochlear implantation is the loss of residual hearing associated with surgery. Hence, many candidates are faced with the decision to relinquish their remaining acoustic hearing in exchange for electric hearing via the cochlear implant (CI). A potential solution is a stimulation strategy termed Electric acoustic stimulation (EAS), which has been used to describe the ipsilateral combination of electric hearing via a CI and acoustic hearing via a hearing aid. This, however, requires preservation of residual hearing, which has been possible but inconsistent. A new technology to potentially improve hearing preservation, intraoperative electrocochleography (ECochG), has been introduced and it was recently implemented into commercially available CI systems. Studies comparing EAS with conventional CI have were able to demonstrate a performance benefit of EAS. However, these studies have compared conventional CI candidates to EAS candidates with more residual hearing. Thus, the clinical importance of residual acoustic hearing in cochlear implantation (CI) remains unclear. Therefore, the present protocol seeks to answer two critical clinical questions in cochlear implantation: (Specific Aim 1) Are cochlear implant electrode insertions using Electrocochleography (ECochG) feedback better for achieving hearing preservation (HP) and (Specific Aim 2) is combined ipsilateral EAS better than non-HP (conventional) cochlear implantation among CI candidates with substantial residual hearing (EAS candidates). We plan to enroll and randomize EAS candidates in seven large US centers. Patients will be assigned to either intraoperative ECochG monitoring or conventional CI electrode insertions. Hearing preservation and other performance outcomes will be recorded and analyzed between the groups to assess the clinical value of intraoperative monitoring. Further, subjects from both groups will have either useable or no useable residual hearing as the result of surgery. Audiometric and patient reported performance outcomes will be obtained and evaluated for 24 months following initial stimulation. In summary, the present proposal aims to answer two critical clinical questions: Is CI electrode insertion based on ECochG better for achieving HP? and Is EAS better than conventional cochlear implantation among EAS candidates? A positive answer to these questions will inform an evidence-based clinical practice for EAS candidates that uses longer electrodes, broadens the candidate pool by including patients with greater levels of residual hearing, and potentially improves outcomes following CI.
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0.951 |