Rene H. Gifford, Ph.D. - US grants

Elderly listeners often experience poorer speech intelligibility than younger listeners, particularly in the presence of noise. Although an age- related reduction in hearing sensitivity likely contributes to this finding, recent scientific research suggests that an age-induced deficit in suprathreshold auditory processing may be present even in the absence of clinically significant hearing loss. Specifically, aging may result in a reduction in the cochlear nonlinearity which in turn may adversely affect suprathreshold processing. The cochlear nonlinearity, which is thought to reflect the functioning of the outer hair cells in the cochlea, is responsible for high sensitivity, sharp frequency tuning, and enhanced spectral contrasts via suppression. Thus, any reduction in the magnitude of the nonlinearity may result in one or more functional deficits, possibly including impaired speech intelligibility. The long-term goal of the proposed research is to further our understanding of the auditory processing of elderly listeners. In particular, this project will evaluate multiple psychophysical estimates of cochlear nonlinearity in young and aged listeners both with normal hearing and with mild- to-moderate hearing loss. For all proposed experiments, two different signal frequencies will be examined, one relatively low and one relatively high; these frequency regions may normally differ in their strength of nonlinear processing and thus differences between young and elderly listeners may be greater at the higher frequency. Thus, the purpose of this study is to examine multiple measures of cochlear nonlinearity in the same group of subjects to determine whether or not an age-related decline in the nonlinearity exists. The ultimate goal is to provide a better understanding of the listening difficulties experienced by elderly listeners.

DESCRIPTION (provided by applicant): Cochlear implant recipients have traditionally performed poorly on measures of speech intelligibility in the presence of noise. Recently, listeners incorporating both electric and low-frequency acoustic stimulation of the same cochlea have demonstrated significant improvements in speech perception in noise that exceed the sum of the intelligibility scores of acoustic and electric stimulation, alone. Thus, the main purpose of this study is to assess whether low-frequency acoustic processing, including frequency resolution, temporal resolution, and cochlear compression, can help account for the synergistic effect of combined electric and acoustic stimulation. Additionally, a subset of these listeners will be examined both pre- and post-implant to investigate the effects of the partially implanted electrode array on tow-frequency acoustic processing including low-frequency quiet thresholds in relatively small, discrete frequency steps, cochlear compression, temporal resolution, frequency resolution, and estimates of speech perception both in quiet and in noise. Both pre- and post-implant measures will be required to accurately assess the effects of the surgery on the apical end of the cochlea.

DESCRIPTION (provided by applicant): In the near future most cochlear implant patients will hear with two 'ears' -- either with two cochlear implants (CI) or with a CI and a hearing aid in the opposite ear (combined electric and acoustic hearing or EAS). The goal of the research proposed here is to develop a tool for clinical decision making relative to these two interventions. Clinical decision making will depend critically on the nature of the tests and environments used to assess the benefit of having two ears participate in speech understanding. Standard clinical test environments can only approximate the real world environment of having sound surround the listener. Laboratory environments with multiple, spatially separated speakers can simulate real world environments but cannot be duplicated in the clinic for reasons of time, space and cost. In this project we will test EAS and bilateral CI patients in both standard and realistic test environments with the goal of creating a decision matrix that links data that can be easily collected in the clinic, e.g., CNC scores in quiet and the amount of residual hearing, with data that cannot be collected in the clinic, i.e., data collected with multiple, spatially separated loudspeakers. We propose to test bilateral CI patients and EAS patients in two realistic test environments using an 8-speaker 'surround sound system' which can simulate, with high fidelity, (i) a restaurant environment with speech babble as the noise, and (ii) a cocktail party environment with competing sentence material as the noise - a situation of 'informational' masking. PUBLIC HEALTH RELEVANCE: This project will allow clinicians to make data-driven decisions about options for hearing restoration in patients who qualify for a cochlear implant. The data will allow clinicians to determine whether two cochlear implants, or an implant plus hearing aid, is the better option.

DESCRIPTION (provided by applicant): In one of the newest applications of cochlear implants, individuals with bilateral low-frequency hearing receive a short electrode array in one cochlea with the aim of preserving hearing in that ear. A successful surgical outcome allows patients to combine electrical (E) stimulation from the implanted ear and acoustic stimulation (S) from both ears or EAS. The long-term goal of this research is to quantify the benefit of acoustic hearing from two partially hearing ears vs. one partially hearing ear - as in the case of bimodal hearing. Previous research has failed to demonstrate significant benefit to speech perception for EAS with two partially hearing ears vs. one partially hearing ear. The standard clinical measures that have been used to assess benefit, however, have not been designed to assess binaural listening. Thus the proposed research will test two groups of patients including (1) EAS recipients, and (2) patients with a conventional electrode array in one ear and low-frequency hearing in the other ear (i.e., bimodal). Experimentation will include complex listening environments which are thought to be sensitive to the use of binaural cues including the spatial separation of speech and noise, reverberation, and localization. The clinical application of this proposal is substantial. Neither audiologists nor otologists are certain how to counsel EAS-qualifying patients about treatment options. This project will provide the necessary information to allow for data-driven counseling. PUBLIC HEALTH RELEVANCE: Combined electric and acoustic stimulation (EAS) with a short electrode array offers a viable treatment option for individuals who do not receive benefit from hearing aids and may not qualify for a cochlear implant due to residual low-frequency hearing. It is critical, however, that both patients and professionals understand the benefits of preserving hearing in the implanted ear as well as the relative benefits of EAS (cochlear implant + binaural acoustic hearing) vs. bimodal hearing (cochlear implant + contralateral acoustic hearing). The current proposal aims to develop this information and, as a consequence, will enable appropriate informed consent for a treatment option that could become a standard surgical tool in the effort to restore hearing to the partially deaf.

DESCRIPTION (provided by applicant): Most modern day cochlear implant (CI) candidates have residual acoustic hearing in one or both ears. Several studies have shown that this residual hearing provides significant benefit when paired with a CI a bimodal listening configuration. The degree of acoustic-related, bimodal benefit however, varies across ears and is not correlated with audiometric threshold, etiology, age or preoperative speech recognition. In the absence of gross differences in preoperative hearing acuity, patients presenting with residual hearing in both ears are commonly told that either ear could provide benefit when paired with a CI. There is no clinical measure that provides predictive utility for selecting the er to be implanted-a critical consideration particularly in cases for which bilateral cochlear implantation may be restricted (i.e. insurance restrictions). This application proposes to develop and implement such a clinical tool. The clinical test of spectral modulation detection (SMD) is a modified version of a validated psychophysical procedure assessing spectral resolution. In this task, the listener is asked to discriminate spectrally-flat noise from spectrally-modulated noise. Pilot work on this clinical procedure has shown SMD in the non-implanted ear is an excellent predictor of acoustic benefit (r = 0.89) when paired with a CI for bimodal hearing. Because this task contrasts noise stimuli, it does not require speech understanding and can be completed by candidates with very little residual hearing-both of which are expected for individuals being evaluated preoperatively. Pilot work with our most recent iteration of the clinical task takes 5 to6 minutes per ear, is highly correlated with acoustic benefit in quiet and noise, and is reported as a percent correct score. This tool has the potential to satisfy a strong need in the fields of audiology and otology as well as significantly influence surgical decisions and patient outcomes.

DESCRIPTION (provided by applicant): In one of the newest applications of cochlear implants, individuals with bilateral low-frequency hearing receive a short electrode array in one cochlea with the aim of preserving hearing in that ear. A successful surgical outcome allows patients to combine electrical (E) stimulation from the implanted ear and acoustic stimulation (S) from both ears or EAS. The long-term goal of this research is to quantify the benefit of acoustic hearing from two partially hearing ears vs. one partially hearing ear - as in the case of bimodal hearing. Previous research has failed to demonstrate significant benefit to speech perception for EAS with two partially hearing ears vs. one partially hearing ear. The standard clinical measures that have been used to assess benefit, however, have not been designed to assess binaural listening. Thus the proposed research will test two groups of patients including (1) EAS recipients, and (2) patients with a conventional electrode array in one ear and low-frequency hearing in the other ear (i.e., bimodal). Experimentation will include complex listening environments which are thought to be sensitive to the use of binaural cues including the spatial separation of speech and noise, reverberation, and localization. The clinical application of this proposal is substantial. Neither audiologists nor otologists are certain how to counsel EAS-qualifying patients about treatment options. This project will provide the necessary information to allow for data-driven counseling.

PROJECT SUMMARY Although the recent literature has indicated that children receiving cochlear implants (CIs) often have dramatically improved speech and language ability relative to previous generations of children with hearing loss, many pediatric CI recipients display persistent speech and language disorders despite early implantation and associated speech/language intervention. There is a striking paucity and ongoing need for studies that systematically examine the relationship between intracochlear electrode location, audiological profile, and subsequent phonological awareness, speech, language, and literacy in pediatric CI recipients. This project provides a unique opportunity to examine whether individualized, image-guided CI programming (IGCIP) significantly improves outcomes in pediatric CI patients. The proposed research activities will examine the impact of personalized IGCIP in pediatric CI recipients on measures of basic auditory function (spectral, temporal, and spectrotemporal resolution), word and non-word recognition, speech production, language, phonological awareness, and reading comprehension using a double blind, waitlist control randomized clinical trial (RCT) design. A total sample of 72 children with CIs aged six to twelve years old will be enrolled in the project: half (n = 36) will be randomized to an immediate IGCIP condition and half to a waitlist control condition. The waitlisted participants (n = 36) will undergo IGCIP after 12 months of monitoring and then followed for an additional 12 months after intervention (total time in the study for both groups: 24 months). Those immediately provided with IGCIP will also be followed for a total of 24 months. All participants will undergo extensive audiological assessment as well as tests of phonological awareness, speech, language, and literacy at baseline as well as at regular intervals: 2, 6, 12, 14, 18, and 24 months. We will use predictor analyses to determine the impact of immediate and deferred IGCIP on subsequent auditory, speech, language, and literacy outcomes.