Emily Buss - US grants

[unreadable] DESCRIPTION (provided by applicant): In recent years there has been a growing body of psychoacoustical evidence demonstrating that stimulus components falling outside of the frequency region of a signal can have a significant effect on the processing of that signal. In profile analysis and in comodulation masking release (CMR) that effect is to decrease thresholds: the presence of flanking stimulus components tends to improve sensitivity. In other phenomena, such as across channel masking, the effect of flanking components is to elevate thresholds. The goal of the current project is to develop a model of across-channel processing that captures both facilitation and interference effects. This model is based on the premise that the most ecologically relevant characteristic of an auditory object is its spectral content as a function of time, and that stimulus conditions associated with synthetic listening (e.g., common onset across frequency) can be understood in terms of the spectral profile, regardless of whether this type of processing is optimal. Further, it is proposed that a psychoacoustical phenomenon demonstrating across-channel processing with amplitude modulated stimulus components, such as CMR, can be understood in terms of short-term spectral cues. Experiments will use standard psychoacoustical methods with human observers to test qualitative predictions of this approach, using paradigms associated with both facilitation and interference. Results will be analyzed using standard parametric statistical techniques, primarily repeated measures ANOVA. Data from these as well as published studies will be modeled in order to obtain quantitative predictions for a range of phenomena involving across frequency masking and masking release. [unreadable] [unreadable]

DESCRIPTION (provided by applicant): The overarching goal of this proposal is to identify and characterize the auditory processes that limit detection and discrimination of spectral cues for stimuli that vary in level, including both normal- hearing and hearing-impaired listeners. Aim 1 examines the effect of stimulus level fluctuation on spectral shape discrimination using the psychoacoustic paradigm of profile analysis. Level rove is often introduced in psychophysical tests of spectral shape discrimination in order to limit the use of absolute level cues, but preliminary data indicate that this manipulation has greater effect above than below 1 kHz. Such a result would have important implications for what we think we know about sensitivity for spectral shape. Aim 2 concerns the relationship between profile analysis and vowel perception, including potential effects of level fluctuation on vowel discrimination. Experiments in this aim will clarify the association between these two paradigms, often assumed to be closely related, and the extent to which psychophysical data on spectral shape discrimination inform our understanding of speech perception. Aim 3 explores the role of temporal fine-structure in masked speech perception, with emphasis on speech recognition in fluctuating noise. Whereas recent studies in the literature provide support for the idea that temporal fine-structure plays a key role in hearing in modulated noise, the proposed experiments introduce control conditions and test plausible alternative hypotheses that have not yet been rigorously evaluated. This issue is particularly pertinent given recent interest in developing cochlear implant technology that preserves fine timing cues. Aim 4 develops novel cuing paradigms that have the potential to provide new insights about our ability to extract signals from fluctuating backgrounds. One goal of this approach is to develop a greater understanding of the preconditions necessary for observing masking release. It is anticipated that the work proposed in these four aims will clarify the role of random level fluctuation in the processing of spectral cues present in natural sounds, such as those underlying speech recognition in background noise. PUBLIC HEALTH RELEVANCE: Level fluctuation can have a marked effect on auditory processing, degrading sensitivity in some conditions and improving it in others. The overarching goal of this proposal is to identify and characterize the auditory processes that limit detection and discrimination of stimuli that vary in level for normal-hearing, hearing-impaired, and cochlear-implanted listeners. Parallel experiments in psychoacoustics and speech perception paradigms are expected to result in greater understanding of basic auditory processes and as well as clinically relevant findings.

DESCRIPTION (provided by applicant): The long-term aim is a better understanding of the auditory processes that enable hearing in background noise, and the effect of early hearing loss on those processes. Aim 1 will investigate the hypothesis that the development of the ability to integrate spectro-temporal glimpses of speech in noise has a protracted development in normal-hearing children, and that such development is even more protracted in children who have long histories of recurrent otitis media with effusion (OME). Aim 2 investigates the relatively novel perspective that hearing loss is associated not only with delays in development and the attenuation of auditory cues, but may also be accompanied by adaptations in auditory processing that enable efficient use of available remaining information. This will be examined both in patients having OME and patients who have severely sloping sensorineural hearing losses. Aim 3 investigates the processing of binaural and monaural acoustical information in patients having severe, unilateral conductive hearing losses. The binaural experiments are aimed at testing how a long history of unilateral hearing loss affects the ability of the brain to analyze and weight information from the two ears. The monaural experiments will investigate whether relatively complex monaural processing is impaired in the ear having history of conductive hearing loss. In patients receiving hearing loss intervention, the binaural and monaural abilities will be tracked longitudinally to determine whether experience results in changes in the ability of the auditory system to weight and analyze information from the two ears. Psychoacoustic studies will use standard, adaptive testing techniques, and speech studies will use a combination of adaptive and fixed block methods. All phases of the project will include age-matched control listeners. Data will be analyzed using analysis of variance and descriptive statistical procedures. There are two ways in which the proposed work relates to public health: 1) the data from the studies on hearing loss will provide information about the effect of early hearing loss on the development of auditory perception; 2) the studies on hearing abilities in normal-hearing children and adults will provide information about human abilities to hear signals in noise, the most common problem experienced by patients having hearing losses.

? DESCRIPTION (provided by applicant): Behavioral assessment is the gold standard for characterizing hearing in infants and children, in both clinical and laboratory settings. Behaviora data play a critical role in the diagnosis and treatment of hearing loss, and they represent our most comprehensive source of information about the time-course of typical auditory development. Despite their practical and theoretical importance, the interpretation of behavioral data is complicated by the contribution of multiple factors, including sensorineural encoding of sound, central auditory processing, and cognitive factors specific to behavioral testing. Disentangling these factors is essential to accurately describing human auditory development, and to the diagnosis of hearing loss and accurate fitting of auditory prostheses during infancy and childhood. The long-term goal of this research is to identify the factors responsible for immature auditory behavior in infants and children, and to develop techniques for differentiating the contributions of these factors in individual listeners. This is accomplished with three specifi aims. The first aim is to test the hypothesis that self-generated noise elevates detection thresholds in young listeners, particularly at low frequencies. The second aim is to evaluate central auditory processing and general cognitive factors limiting performance of young listeners, including memory for pitch and loudness, the ability to listen selectively in frequency r time, and the ability to capitalize on the context present in a closed-set speech recognition task. The third aim is to evaluate novel procedures for improving behavioral assessment of hearing in infants, toddlers, and `hard-to-test' children with hearing loss. The proposed work is of theoretical and clinical significance, in that it examines how the various factors contributing to auditory behavior limit performance across age and within individuals. The results obtained are expected to advance assessment methodologies in clinical and basic science settings.