Tiffany Johnson, PhD
Characterizing the Effect of Stimulation Parameters on DPOAEs Recorded in Normal and Impaired Ears
Distortion product otoacoustic emissions (DPOAEs) are widely used to screen for hearing loss. While the accuracy with which DPOAEs identify auditory status is good, errors in diagnosis are made. In particular, ears with mild hearing losses are frequently misidentified as having normal hearing. Significant effort has been devoted to characterizing the influence of stimulus parameters on DPOAEs recorded in normal-hearing ears; however, less effort has been devoted to exploring the same parametric space in hearing-impaired ears. While stimuli that maximize DPOAE levels in normal-hearing ears are commonly used to screen for hearing loss, there may be clinical utility in choosing stimuli that maximize the differences in responses recorded from normal and impaired ears. In this proposal, we describe a study designed to complete a broad exploration of the stimulus parametric space in ears with mild-to-moderate hearing loss, in order to more fully characterize the influence of DPOAE stimulus parameters in impaired ears. In a second study, DPOAE levels recorded in impaired ears will be compared to those recorded in normal ears under identical stimulus conditions. These results will be used to identify the stimulus conditions producing the maximum separation between responses recorded from normal and impaired ears. |
Sonja Pyott, PhD
Enhancement of the Efferent-Hair Cell Synapse by Metabotropic Glutamate Receptors
The mammalian cochlea has two types of specialized sensory cells that are distinguished by their synaptic connections with the central nervous system. Inner hair cells have abundant afferent innervation that transmits information about sound to the central nervous system. Outer hair cells, in contrast, are almost exclusively innervated by efferent projections from the central nervous system. Experiments studying immature inner hair cells suggest that glutamate, the neurotransmitter mediating the afferent synaptic response, may also modify the efferent synapses. Specifically, agonists of the metabotropic glutamate receptors (mGluRs) enhance the efferent synaptic response. The established role of mGluRs in the central nervous system in combination with these preliminary findings, suggest that mGluRs may be involved in a feedback loop between the hair cell and the central nervous system. This research project will use electrophysiological recordings of hair cells from neonatal rats to investigate this hypothesis. The three specific aims of this research are to: 1) verify that glutamate released from the inner hair cell enhances the efferent-inner hair cell synaptic response via the activation of mGluRs; 2) characterize the mechanism of enhancement of the efferent-inner hair cell synaptic response by mGluRs; and 3) determine whether enhancement of the efferent synaptic response by mGluRs also occurs at the efferent-outer hair cell synapse.
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Christina Roup, PhD
Monaural vs. Binaural Word Recognition Among Older Adult Listeners
A growing body of evidence suggests an age-related decline in the ability to process binaural auditory information in a competitive listening environment. This decline has been associated with a lack of benefit from binaural amplification, a common form of audiologic rehabilitation for older adults with sensorineural hearing loss. The current proposal focuses on measures of speech recognition that assess the binaural auditory system. Both a left-ear disadvantage for dichotic listening and an age-related deficit in the recognition of speech in a competing message have been described for older adults; few studies, however, have reported results of performance on both measures in the same group of listeners. The specific aim of the proposed research is to investigate the relationship between dichotic and competing message word recognition among the same group of older adult listeners. The proposed research will examine the relationship between dichotic word recogntion and word recognition in a competing message across three age groups of older adults (60-69 years, n’l0; 70-79 years, n=10, 80-89 years, nl0) with mild to moderately-severe sensorineural hearing loss. Comparisons will be made between performance patterns for dichotic word recognition (e.g., a left-ear disadvantage) and word recognition in a competing message (e.g., monaural vs. binaural performance). |
Gary Christopher Gaines, II
Gravity Receptor Neural Adaptation During Repetitive Exposure to Acceleration Transients
Deficits in the inner ear vestibular system are one major reason for dizziness and balance disorders. The present application proposes to study the vestibular system’s adaptive capability to short-term repetitive exposure to acceleration transients. Specifically, we will test the following hypothesis: Short-term exposure to linear acceleration transients (repetitive 4G stimulus) will modify mammalian vestibular neural function. To test this hypothesis, we will measure VsEPs in two groups of age matched mice (C57/BL6J strain). One group will undergo a short-term (one hour) exposure to transient linear acceleration pulses (40 acceleration) and the second control group will not experience this stimulus exposure. VsEPs will be measured before exposure and at 15 minute intervals during the exposure time period. VsEPs will also be collected from control animals at 15 minute intervals; however, these animals will remain still during the time points between measurements. Following data collection, VsEP waveforms will be plotted and the first three positive and negative response peaks will be scored. Response peak latencies (i.e., P1, P2 and P3), which reflect neural activation and conduction timing, will be measured and analyzed across time and will be compared between the stimulus and control groups. Response peak amplitudes (P1-Ni, P2-N2 and P3-N3) will also be measured and compared between groups. These results will give us new, fundamental insight into vestibular functional changes relative to the stimulus environment and may ultimately lead to improved treatments for dizziness and balance disorders, particularly those resulting from inner ear deficits.
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Junghwa Bahng
Acceptance of Noise in Adult Cochlear Implant Users
Acceptable noise levels (ANLs) and the Hearing in Noise Test (HINT) were examined in nine adult CI users and 15 normal-hearing listeners. The Abbreviated Profile of Hearing Aid Benefit (APHAB) and a satisfaction questionnaire were administered to CI users. ANLs were (1) not different between groups, (2) not related to HINT scores and (3) correlated with CI benefit on the questionnaire, suggesting ANL can be useful when examining processing in noise in CI users. |
Sarah King, BS
TIMIT List Equivalence by Cochlear Implant Recipients
The present study, supported by the NIH, was designed to evaluate the equivalence of intelligibility by cochlear implant recipients of 34 TIMIT sentence lists created from the TIMIT speech database where sentences differ by speaker gender, regional dialect, and speaking rate. Data collection and analysis will determine whether the TIMIT sentences should be recommended for either clinical or research purposes and if so, which lists are comparable. |
Nicole Kreisman, PhD
Psychosocial Impact of APD: Implications for Audiologists
The present investigation examined the relationship between auditory processing disorders (APD) and psychosocial health status in children. Psychosocial health status was evaluated via the Dartmouth COOP Charts for Adolescents, the Behavioral Assessment System for Children, Second Edition (BASC-2) and the Social Skills Rating System (SSRS). Results from questionnaires given to both children and their parents indicated that children with APD had significantly greater difficulty with emotional, behavioral, and social function than children without APD. |
Lisa G. Potts, PhD
Bimodal Hearing: Localization and Speech Recognition
This study documents the effect of wearing a cochlear implant in one ear and a hearing aid in the opposite ear (bimodal hearing). Binaural summation occurred for soundfield thresholds and loudness growth contours in the bimodal condition. Localization and speech recognition were significantly better in the bimodal condition compared to the monaural conditions. Speech Sound Qualities questionnaire responses and audibility of sound with the hearing aid were significant predicators of localization and speech recognition abilities. |
Jay Sheehan, AuD
Outcomes of FM System Usage in Places of Worship
Psychosocial impact of six months experience with FM system in places of worship was studied in 23 hearing aid users. Outcomes were assessed in dimensions including disability, handicap, health-related quality of life, psychosocial impact, and spiritual well-being. Written administrations were measured at baseline and at 12 and 24 weeks into the experience. Significant differences in benefit and satisfaction when the FM was added to the hearing aid were documented during this study. |
Sarah Borton, BS
Quality of Life in Children with Unilateral Hearing Loss
The purpose of this investigation was to determine the impact of unilateral hearing loss (UHL) on the quality of life of children. Two methods were used: (1) focus group sessions were held for parents and children or adolescents with unilateral hearing loss to discuss their perceptions and (2) parents and children or adolescents completed the Pediatric Quality of Life Inventory. Findings were presented depicting which domains of life are most affected. |
Cynthia DeMots, BS
Effects of Auditory Toughening in Rats
This study evaluated the effects of auditory toughening, i.e., conditioning an animal to a low-level intermittent sound prior to a traumatic noise exposure. Hearing thresholds and outer hair cell (OHC) function were measured prior to, immediately following, and 12 days after exposure to a pure tone stimulus at increased levels in conditioned and non-conditioned rats. The conditioned group was more resistant to damaging sounds as compared to a control group. |
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