Sumitrajit Dhar - US grants

DESCRIPTION (provided by applicant): Otoacoustic emissions (OAEs) are signals generated in the cochlea, presumably as a byproduct of active physiological processes responsible for normal functioning of the ear. Distortion product OAEs (DPOAEs) are recorded by stimulating the cochlea simultaneously with two pure tones. A model in which DPOAEs recorded in the ear canal are represented as a composite signal comprised of contributions from several components has been proposed by Talmadge et al., (1998). Research recently has focused on the examination of specific properties of individual DPOAE components identified in this model. The goals of this study are to investigate the effect of input level on the main DPOAE components, and to examine the existence of multiple internal reflections in the cochlea as stimulus level is varied. Additionally, the data obtained during these experiments will allow the estimation of several model parameters. Overall, the results of these studies will improve our understanding of the DPOAE generative mechanisms and the basic mechanics of the cochlea. Such knowledge will invariably improve our ability to use DPOAEs as both a clinical and a research tool.

DESCRIPTION (provided by applicant): As a society and nation we are increasingly aware of the value of preventive medicine. In the area of hearing health, prevention is achieved by awareness of elements hazardous to hearing and the early diagnosis of small changes in hearing status. The current diagnostic protocol used in audiology has been in place for over half a century and is insensitive to small changes in auditory physiology. We propose to evaluate novel methods of detecting alterations in hearing status. These novel methods are implemented within a test-battery that should effectively evaluate several aspects of hearing function and relate to communication difficulties experienced by individuals in the real world. Work during the first phase of the project evaluates the effectiveness of a new diagnostic system currently under development in our labs and examines the efficacy of methods of calibration, as well as recording of stimulus frequency otoacoustic emissions. This system will integrate the administration of all tests proposed here and be able to administer them over an unprecedented range of frequencies. The results of this phase are incorporated into a second phase where a battery of tests is evaluated in an age-distributed group of 400 subjects. In the final and largest phase of the study, we glean the most effective tests from the previous phase and evaluate their efficacy in a battery, as well as individually, on a sample of 1200 subjects. This phase is conducted over the last three years of the project period, at three sites. Two of the proposed study sites are functional audiology clinics in university and medical environments, respectively. Consistent with the translational goals of the project we develop a new measurement device which incorporates new methods of evaluating the auditory system. We evaluate these tests in a large cohort of diverse subjects. Finally, we engage in aggressive, evidence-based promotion of these new technologies and methods, as suggested by the overall findings of our study.

DESCRIPTION (provided by applicant): Many older adults experience excessive difficulty perceiving speech in background noise. Why this occurs for some, but not all older individuals is a question that currently has no answer. Our long-term goal is to understand the biological bases of speech-in-noise perception in older adults and to use that knowledge to improve perception through training. Converging evidence indicates that the auditory sensory system (including cochlear mechanics and brainstem) is dynamic and can be shaped by short-term (training) and lifelong (language and music) experience. Normal verbal communication depends on the accurate transcription of sound by the nervous system, especially in noisy backgrounds. Failure of this transcription process in the aging population represents a huge social and financial cost, and considerable resources are invested in treatments that may not work. Little objective assessment exists in diagnosis and evaluation of treatment options. Further, there is emerging evidence that the auditory periphery is modulated by higher centers via the efferent system to aid listening in background noise. This contribution remains to be characterized and/or quantified in any detail in the human species. Accordingly, our objectives are to determine brainstem transcription of speech sounds in noise in older adults, how this transcription relates to measures of cochlear mechanics, and the plasticity of transcription with training. Our central hypothesis is that disruption of transcription accuracy and cochlear mechanics are factors in listening-in-noise impairments, and that disruption can be remedied by intervention. The outcome of the proposed work will reveal sensory mechanisms linked to speech perception in noise in older adults and determine plasticity of basic sensory circuitry arising from short-term training. This outcome will have a positive impact on our understanding and objective assessment of sensory function in aging adults. PUBLIC HEALTH RELEVANCE: Normal verbal communication depends on the accurate transcription of sound by the nervous system, especially in noisy backgrounds. Many older adults experience excessive difficulty understanding speech in background noise because, at some level, the transcription process has broken down. Our first objective is to investigate the earliest levels of transcription-cochlear mechanics and brainstem encoding - and determine the extent to which they may contribute to the problem, thereby potentially leading to an objective metric. The second objective is to investigate the extent to which a training-based remedy affects these early processing levels. This outcome will have a positive impact on our understanding and objective assessment of sensory function in aging adults.

DESCRIPTION (provided by applicant): Current United States Food and Drug Administration (FDA) policies for adults seeking to purchase hearing aids balance two potentially conflicting healthcare objectives: (1) ensure public safety by detecting sinister ear disease prior to hearing aid purchase, and (2) make hearing aids and other hearing healthcare services more affordable and available. Two disease surveillance policies have evolved, reflecting this dichotomy. The FDA preferred surveillance method requires that consumers obtain a pre-hearing aid purchase medical evaluation. This is assumed to provide optimal disease detection - at the potential cost of decreased affordability and availability of hearing healthcare services. Although formally discouraged, consumers can waive the medical evaluation, thereby potentially increasing accessibility of hearing healthcare services - at the potential cost of missing sinister ear diseas. The two FDA provisions are contradictory and there is little empirical evidence to support either as an effective public health policy or to inform alternative disease surveillance approaches. When the medical waiver option is exercised, the burden of detecting ear disease falls upon the consumer and the non-physician hearing healthcare provider (e.g. audiologist or hearing aid specialist) who provides the hearing aids. How well can audiologists detect ear disease? How well can consumers assess their own risk for ear disease? These two key questions must be addressed to answer the broader query posed by NIDCD: Do the existing FDA requirements for medical evaluation and clearance prior to hearing aid procurement provide significant protection to patients or create a significant barrier to access? We propose to empirically evaluate how well non-physicians (consumers and, in this case, audiologists) can evaluate ear disease risk, by developing and testing the performance of two questionnaire-based tools - one consumer focused (Consumer Ear Disease Risk Assessment or CEDRA) and one provider focused (Provider Ear Disease Risk Assessment or PEDRA). They are designed to be easy to complete, sensitive to ear disease risk factors, and result in a score that can be translated into statistical estimate of ear disease likelihood. CEDRA will consist of questions that focus on recognition of ear disease symptoms. PEDRA will include similar questions, and will also include innovative data analysis tools, developed at the Mayo Clinic, which enhance recognition of otologic disease risk factors in standard audiometric test data. The accuracy of CEDRA and PEDRA based disease screening will be evaluated against the judgments of otologists and neurotologists in a prospective, multisite study involving academic medical facilities across the United States. If CEDRA and PEDRA are found to accurately screen for ear disease, these tools might become useful to safely guide a consumer's decision to use the medical waiver - making hearing aids more affordable and accessible when disease risk is low. If ear disease cannot be detected using these tools under the optimal conditions of this study, the safety of the medical waiver option would have to be challenged.

The Research Management & Experimental Tools (RMET) core addresses three critical goals: i. increase efficiency by centralizing resources frequently duplicated across laboratories; ii. augment innovation by combining best practices across laboratories; and iii. accelerate translation by developing common platforms across research groups ranging from the basic to the applied. These goals will be addressed through three specific aims: 1. Develop a central human subject management tool. A secure web-based application will be developed to support all aspects of recruitment and scheduling. 2. Develop a set of core tools forgathering data across multiple experimental domains. A common, open source, platform-independent experimental software platform will be made available to support common tests across laboratories. 3. Develop a large-scale database for project data. A secure, robust relational database will be developed to allow co-registration of demographic data and behavioral data from both the screener developed by Core 1 (Human Subject Recruitment & Management) as well as additional tests used across laboratories. The human subjects management system will provide a secure way to address common recruitment needs through shared resources. Leveraging experience across laboratories will allows us to develop a high quality set of experimental tools that can be shared with the entire research community. Both of these computational tools, coupled with a large-scale database for project data, will provide a technical infrastructure that can facilitate synergistic research across a wide variety of laboratories.