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2011 Research Abstracts

Kristi A. Buckley, PhD
Sensory Integration and Sensory Interference in Individuals with Hearing Impairment and Individuals with Normal Hearing

The perception of speech information normally includes both visual and auditory information. It has been shown that integration of visual information with auditory information is beneficial to most individuals when the auditory signal is degraded, as is the case in hearing impairment or noisy environments. It has also been demonstrated that in difficult listening situations, individuals with hearing impairment rely more heavily on the visual signal than individuals with normal hearing. Conversely, it has been demonstrated that individuals with hearing impairment have more difficulty understanding speech in situations where a visual distracter is present. Thus, both enhanced sensory integration and enhanced sensory interference between the visual and auditory systems have been demonstrated in hearing impaired listeners, and our understanding of the interactions between the visual and auditory systems remains unclear. We propose to explore the relationship between visual and auditory system interaction in language and non-language related tasks from both a sensory integration and sensory interference perspective in individuals with normal and impaired hearing. This investigation will further our understanding of the complex relationship between these sensory systems.

Yu-Hsiang Wu, MD, PhD
Establishing a Conceptual Model of the Acceptable Noise Level Test (ANL)

The goal of the proposed research is to establish a conceptual model that elucidates the mechanism underlying the Acceptable Noise Level Test (ANL). This is to be achieved by investigating whether the perceived signal-to-noise ratio (SNR) is the criterion used by listeners to make ANL judgments (Specific Aim 1), and by investigating the effect of visual inputs on the ANL. The ANL is a measure that determines the maximum noise level that a listener is willing to accept while listening to speech. Despite the growing use of the ANL in clinical settings and research endeavors, no comprehensive theory exists to explain the mechanism of the ANL, that is, what factors constitute the ANL and how these factors are perceived by the listener. The purpose of this research is to establish a conceptual model that clarifies what contributes to a listener's determination of the highest acceptable background noise when listening to speech. To test the hypothesis that the perceived SNR is the ANL criterion, listeners' aided ANL scores when using various hearing aid technologies will be measured and compared to the scores predicted from unaided ANL scores using the functions that describe the relationship between hearing aid input SNR and output SNR. To investigate how inputs from multiple sensory modalities impact ANL judgments and to examine the relationship between ANL and speech perception (Specific Aim 2), the ANL and speech perception scores will be measured with and without the presence of visual cues and in conditions with various auditory-visual asynchronies.

Karolina Charaziak, MS
Relating Physiological and Perceptual Measures of Frequency Selectivity

This investigation aims to develop a noninvasive and objective tool for assessing frequency selectivity in humans. The goal is to obtain data for normal hearing and hearing impaired subjects validating stimulus-frequency otoacoustic emission suppression tuning curves as an objective measure of frequency selectivity against psychophysical tuning curves. Frequency selectivity is a basic parameter of auditory function. Its deterioration has far reaching consequences for perceiving complex sounds as speech in noise. In humans, frequency selectivity is estimated based on behavioral tests as measurements of psychophysical tuning curves (PTCs). However, such tests require subject cooperation, so are not appropriate for many populations. On the other hand, noninvasive tests of cochlear function, namely otoacoustic emissions (OAEs) recordings, can be easily applied independently of subject attentional state or ability to cooperate. Stimulus-frequency (SF) OAE suppression tuning curves (STCs) are measured in analogous way to PTCs. Given that frequency selectivity is primarily established at the level of the cochlea and suppression is one of the main physiological mechanisms underlying auditory masking SFOAE STC and PTC should result in a very similar estimates of frequency selectivity. To test this hypothesis SFOAE STCs and PTCs will be measured in normal- and hearing-impaired subjects across signal frequencies and levels in order to verify if the two estimates of frequency selectivity are influenced by signal parameters in parallel way. This study will provide promise for developing an objective measure of frequency selectivity that is easy to perform, time efficient and unbiased by cognitive factors as attention.

Michelle Hsieh, AuD
Physiological and Psychoacoustical Sensitivity to Amplitude and Frequency Modulation in Normally Hearing and Hearing-Impaired Listeners

Previous researchers have found a correlation between the strength of the auditory steady state response (ASSR) and corresponding behavioral measurements such as speech recognition scores (Dimitrijevic et aI., 2001), thus providing an objective measurement of auditory supra-threshold properties. However, relatively few studies have directly investigated the relationship between the ASSR and sensitivity to small changes in amplitude and frequency modulation depth in comparable stimuli. In the present study, we hypothesized that physiological differences in sensitivity to amplitude and frequency modulation depth will be reflected in corresponding psychophysical measures. Auditory steady-state responses will be collected in response to amplitude and frequency-modulated pure tone carriers (500 and 3000 Hz) in normally-hearing and hearing-impaired listeners over a range of modulation depths at modulation rates of 40 and 80 Hz. Participants will complete a series of modulation discrimination tasks in which the smallest amount of amplitude or frequency modulation needed to differentiate from a standard amount will be measured in a 2IFC paradigm over the same range of modulation depths. The relationships between the ASSR and the psychophysical performance will be investigated in both groups of listeners.

Kensi M. Cobb, BA
Effect of Altered Auditory Feedback on Stuttering Duration and Type in Adults Who Stutter During Conversation

The broad, long-term objective of this line of research is to explore the link between audition and speech production. Historically, auditory contributions to speech production have been discounted. Borden (1979), for example, argued that the auditory system was too slow for online monitoring of speech production. More recently, with the advent of sophisticated electrophysiological technologies, a renewed interest has developed examining the link between speech production and audition. More contemporary models of speech production account for involvement of the auditory system via feed-forward and feedback control subsystems (e.g.,Guenther, Ghosh, & Tourville, 2006). This includes both normal and abnormal speech production. Stuttering is one such case of abnormal speech production where audition has long been thought to play a role. Over the past several decades, there has been a renewed interest in stuttering that brings this "neurophysiologic speech disorder" into the realm of audio logic research. Imaging studies have implicated the role of the auditory system on a central level in stuttering (e.g., AIm, 2004; Foundas et a1., 2001, 2003, 2004; Giraud et a1., 2008; Sommer et a1., 2002). Researchers have also renewed their examination of the effects of altered auditory feedback (AAF) on the overt manifestations (i.e., the stuttering moments) of the disorder. This includes variables, such as the frequency, duration, and type of stuttering events. The aim of this Student Summer Research Fellowship is to provide a research experience for the student whereby they further examine the effect of AAF on the spontaneous/conversation speech production of people who stutter (PWS).

Gary C. Gaines, II, AuD/PhD Candidate
Neural Generators of Mammalian Vestibular Responses to Linear Head Motion

The purpose of this project is to evaluate the candidate neural generators of the vestibular sensory evoked potential, VsEP, in the mouse model. The linear vestibular sensory evoked potential (VsEP) is thought to be the compound electrical response of peripheral macular neurons and central neural relays and as such, is used to directly assess macular function. The VsEP is used in animal research to study, among other things, the genetic basis of deafness and balance disorders. Although the neural generators of the linear VsEP have been described in the bird (Nazareth and Jones 1998), the precise central neural generators have not been documented for the mouse model. Because the mouse is such a valuable model, it is important to clearly identify the peripheral and central generators ofVsEPs in mice. We will record VsEPs before and after strategic surgical manipulations of vestibular pathways. This includes isolation of the eighth nerve from central relays and destruction of central candidate neural generators. The extent of lesions will be characterized histologically. Changes in response components will be documented. Response components critically dependent on particular central structures will be identified. These studies will increase our understanding of the neural generators of the VsEP, and in turn, enhance our ability to assess peripheral and central vestibular function and detect vestibular disease.

Alyssa Baker, BA
Auditory Phenotype of McCune-Albright Syndrome

McCune-Albright Syndrome is a non-inherited disorder defined clinically by the triad of polyostotic fibrous dysplasia (PFD), café-au-lait pigmentation, and premature puberty. PFD may involve the temporal bone with subsequent deleterious effects on the auditory system. Limited case reports suggest both conductive and sensorineural hearing loss in those with PFD. We present a comprehensive characterization of the auditory phenotype and middle ear transmission characteristics in 113 individuals with MAS.

Erika Becker
The Role of Insurance Coverage in Hearing Aid Acquisition

Accessibility to affordable hearing care is presumed to be a factor in the disparity between need for hearing aid use and its adoption. We evaluated the amount of hearing loss and the age at which hearing aid use was sought as a function of hearing aid insurance coverage. Results showed that those patients with full coverage had significantly less hearing loss and sought hearing care at a significantly younger age than those without coverage.

Gary C. Gaines, II, AuD/PhD Candidate
Effects of Ketorolac on Linear VsEPs and ABRs in Mice

The use of ketorolac during surgery is believed to reduce the anesthetic dose required to achieve and maintain an adequate surgical plane and thus improve the physiological conditions and survival of animals during long experimental procedures. The present results reveal that VsEP and ABR peak amplitudes generated by both the periphery and central portions of the auditory and vestibular pathways remained stable over time with normal dose volumes of ketorolac.

Rachel Loveless, AuD
Audiologic Knowledge and Practice of Genetic Consultation for Children with Congenital Hearing Loss

Despite guidelines asserting that every child with congenital hearing loss should be referred for genetic consultation, it is unclear whether audiologists are referring. The current study analyzed audiologic practice patterns and knowledge of the genetics of hearing loss, and results indicate less than half of audiologists are regularly referring for genetic consultation, and many may lack a base knowledge in genetics. Significant differences in referrals and knowledge were seen among different groups of audiologists.  

Chiemi Tanaka, PhD
Age-Related Changes in Expression Patterns of Cochlear Oxidative Stress-Related Genes in Fischer 344/NHsd Rats

Although oxidative stress is thought to be a major contributor to aging, its contribution to presbycusis is not fully understood. The current study investigated the effects of age on the expression patterns of cochlear oxidative stress-related genes in Fischer 344/NHsd rats, animal model of presbycusis. The genes reported to increase their expression in response to oxidative stress were significantly unregulated, suggesting a presence of oxidative stress in the aging cochlea possibly leading to presbycusis.

Barbara Heinze, M(ECI)
Auditory-Vestibular Pathology Associated with HIV/AIDS

A cross-sectional quasi-experimental study of auditory-vestibular pathology in a group of HIV positive adults (n=55) was conducted in a South African hospital and compared to a control group of HIV negative adults (n=15). Participants were evaluated with clinical assessments including audiometry, vestibular bedside assessments, video nystagmography, and VEMP. Results indicate a high prevalence of auditory-vestibular pathology including conductive and sensorineural hearing loss (52 percent), peripheral vestibular pathologies (68 percent), and signs of central vestibular pathologies (48 percent).

Hannah Kim, BA
Test-retest Reliability of Open Hearing Aid Fittings in Children

Currently, there are little test-retest reliability data on real ear measures of open fittings. Real ear verification procedures in open fittings are expected to introduce new sources of variability. This primarily includes the use of stored equalization for calibration which could be especially problematic in children, who are likely to move around during verification procedures. This project examined the test-retest reliability of real ear occluded and aided responses for open fittings in children ages four to 13.

Jay Vachhani, BS
Comparing Speech-Evoked Auditory Brainstem Responses between the Cz and Fz Montage

The purpose of this study was to observe if the Fz montage generates comparable responses as the Cz montage for the speech-evoked auditory brainstem response. The latency and amplitude information from the transient and sustained responses were measured from eight subjects using the BioMARK application. A significant difference in some amplitude data was found. This difference has important clinical implications for objectively assessing auditory function.

Mostafa Youssif, MD, MS
Normative Data on Vestibular Evoked Myogenic Potential in Children

Pediatric vestibular dysfunction is under diagnosed due to the lack of standardized tests and challenges in evaluating children. The purpose of this study was to collect normative data for vestibular evoked myogenic potential (VEMP) in children. VEMPs were collected from forty normal children between three and 12 years of age. Results suggest that there is no significant difference across the age groups for the children. However, the latencies are significantly shorter than adult latencies.

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