Frederick J. Gallun - US grants

[unreadable] DESCRIPTION (provided by applicant): PROJECT SUMMARY This research will examine the ability of listeners to make multiple rapid judgments about non-speech auditory stimuli. These stimuli will vary simultaneously and/or sequentially on three dimensions: amplitude, frequency and perceived location. Recent work on the ability of hearing-impaired listeners to process rapid, noisy speech (e.g. McCoy et al., 2005) has identified deficits that exist independent of the ability to understand and remember more clearly presented speech. This study will examine the processing of rapid and simultaneous stimulus changes in a design that does not require listeners to make use of any specific language-related mechanisms. The hypothesis to be tested is that the ability to make multiple judgments depends on short-term memory and the availability of processing resources. Specific aims involve 1) examining the role of temporal relationships between stimuli (simultaneous vs sequential), 2) comparing the ability to make multiple judgments within a frequency region with the ability to do so across frequencies and 3) examining the hypothesis that different types of interference occur when listeners try to make several judgments in sequence as opposed to when they must hold the target stimuli in sensory memory to make a comparison with a delayed cue. RELEVANCE Listeners in constantly changing environments often experience more difficulties than when the same noise level is present but the environment is not changing so rapidly. This is a particular problem for those with even mild hearing loss. By improving our understanding of the processes by which a rapidly changing auditory environment is analyzed, we hope to improve our ability to create appropriate therapies and devices to reduce the difficulties hearing-impaired listeners experience. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Of the 36 million hearing-impaired Americans, 21 million are over 45 years of age, and 35-40% of persons over 65 years of age are hearing-impaired. As the population ages, the number of Americans who are both older and hearing-impaired will only increase. Despite decades of research on speech understanding in noise, there is no theoretical explanation for the increased difficulties older hearing- impaired listener have in multitalker environments as compared to their younger counterparts. This fundamental gap in our knowledge makes it impossible to address clinically the devastating effects of an inability to communicate in social environments such as restaurants, the workplace, and many retail environments. These effects include increased self-perception of handicap and social withdrawal. This research program will seek to determine whether or not speech perception ability in multitalker situations can be predicted by measuring sensitivity to spatial, spectral, ad temporal information. The clinical significance of the research proposed is related directly to the ability to predict how successful an individual listener will be in a given multitalker environment Despite the evidence that binaural hearing, sensitivity to temporal information, and sensitivity to spectral information are impaired in listeners with hearing impairment, and the fact that tests have been developed for the clinic that are intended to be sensitive to these abilities, there are very few clinical audiologists who routinely test these abilities as part of their audiometric examination. If it can be demonstrated which subset of these clinical tests are accurate predictors of speech recognition in a multitalker background, the knowledge gained will allow the clinician to more accurately predict the expected clinical benefit of a particular hearing device for a specific user in various environments. This will allow the clinician to choose and fit hearing aids more successfully and to counsel patients more effectively in terms of the benefit they should expect in various environments. Similar benefits to patient care will be obtained by providing this information to the developers of hearing aid technology and rehabilitative training programs, who could then develop specific devices and techniques to address those deficits that occur most often.

? DESCRIPTION (provided by applicant): Most diagnoses of hearing loss focus on the audiogram, which is not sensitive to dysfunction at many of the additional processing stages associated with auditory perception. For example, recent data from many laboratories, including our own, have shown clear auditory processing deficits both in older listeners and in patients who have suffered traumatic brain injury, despite normal audiograms. Modern auditory neuroscience, computational modeling, and psychoacoustics have provided great insight into the information processing that underlies auditory perception and have identified specific stimuli and tasks for the evaluation of central auditory function, but this information has largely remained in the laboratory. It is the goal of this proposal to develop and evaluate a set of clinicl tests that draw upon modern laboratory tests and theories of auditory system function. These will form the basis of a new clinical test battery for central auditory dysfunction that will suppot the accurate diagnosis of a much wider range of the difficulties that can lead to auditory complaints.

Project Summary The overall objective is to develop and test a novel rehabilitative training program for central auditory dysfunction after traumatic brain injury. Solutions designed to enhance auditory processing when hearing thresholds are within normal limits are very limited and none are as recognized or as widely available as are hearing aids and cochlear implants. While there exist some contemporary approaches devised to improve hearing in a variety of populations, these are largely based upon emulating hearing scenarios in the environment. While such programs show some efficacy, three key limitations undermine the overall effectiveness and deployment of these approaches. 1) A lack of alignment of treatments with up-to-date knowledge of how sounds are processed by the brain 2). A lack of alignment of treatments with up-to-date knowledge of perceptual learning research, and 3) Difficulty in getting patients to comply with training procedures that are often frustrating and boring. Here we aim to overcome these limitations by integrating contemporary knowledge of auditory neuroscience, perceptual learning, and modern game design to develop and test novel auditory training therapies. Our primary premise is that 1) Studies of auditory neuroscience and psychoacoustics have advanced our understanding of the function of auditory processes beyond the cochlea. 2) Studies of perceptual learning have advanced our understanding of plasticity in the neural systems underlying hearing, and have refined behavioral procedures that engage these systems. 3) Commercial video games have become ubiquitous, sophisticated, and shaped by competitive market pressures to become both perceptually engaging (rich graphics, sounds, and animations) and cognitively challenging. Combining these elements can lead to behavioral cognitive therapies that are effective and encourage compliance by being compelling, stimulating, and fun. We will test an adaptive training program that involves practice with a ?basis set? of spectral temporal modulated sounds that are modeled after auditory neuron receptive field properties7 combined with interaural localization cues to also train sound source segregation. Efficacy will then be tested in normal hearing participants and in patients with mild traumatic brain injury and auditory processing difficulties (APDs) and compared against active tone training controls. Outcome measures are tests of real world audition including; speech in noise, multiple talker environments and auditory attention and working memory. Potential for knowledge gain and translational impact is substantial. This project will result in techniques and data relevant to rehabilitation of APDs. The data and training will be made available to the clinical and research community. Evidence of efficacy will be followed upon with a R01 proposal to examine how different components of training contribute to observed effects and to examine neural underpinnings. The positive impact whether or not the training program is effective will be new knowledge about what types of training programs are effective, and which are not, and can contribute to development of effective therapies for APDs.

Project Summary Speech in noise tests have traditionally involved 1) unrealistic maskers such as broadband noise presented from the same spatial location as the target speech, and 2) unengaging reward structures. Our overarching hypothesis is that the experience of listeners in their daily lives will be more strongly related to performance if the laboratory tests are enhanced by increasing the realism of the testing environments and introducing game- like interfaces. The main goal of this project is to determine which enhancements have the greatest impact on the relationship with listener complaints, and which listener abilities (auditory and cognitive) mediate and modulate this relationship. Enhanced environments will be tested that 1) simulate real-world experiences by conducting assessments in synthetic environments that include both auditory and visual stimuli and 2) introduce game-like elements that are more rewarding and motivating for the listener. Understanding how different participants respond to a variety of enhancements will provide essential new information about the ways in which realistic experiences differ from traditional laboratory tests and the ways that rewards and motivation influence variability of test results as well as relationships with self-report. Experiments will involve younger listeners with normal hearing, older listeners with a range of hearing abilities from normal to severely impaired, and a group of listeners with a history of mild traumatic brain injury. These participants will provide a wide range of performance on measures of auditory and cognitive abilities, which can then be used to better understand any effects of the enhancements on self-reported ability to function in complex listening environments. Upon completion of this project there will exist, freely available, an extensive set of enhanced auditory assessments that are more engaging and more realistic than what is currently available and that run on inexpensive consumer-grade equipment. This project will establish for these enhanced tests both 1) established ranges of normal performance as a function of age and hearing loss, and 2) known relationships to various established tests of speech in noise. The modeling work associated with this project will reveal which auditory and cognitive abilities are associated with deviations from normal performance and self-reported difficulties hearing in adverse listening environments that are great than would be expected.