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2013 Research Abstracts

Gavin Bidelman, PhD
Central Neurophysiological Markers Underlying Degraded Speech Recognition

Recognizing speech within the auditory scene is constantly challenged by interfering noise. Noise-exclusion is particularly problematic for the elderly and hearing impaired who perform poorer in noise than their hearing loss would predict. While modern hearing aids provide audibility, they fail to restore speech intelligibility in noisy/reverberant settings. Advancements in assistive hearing technologies could be dramatically improved with knowledge of how central brain mechanisms affect speech coding in adverse listening situations. Using an innovative electrophysiological approach, brainstem and cortical neuroelectric responses will be recorded concurrently in human listeners elicited by speech with and without acoustic interference. We aim to 1) characterize how noise alters the neural representations and subsequent perception of important speech cues and 2) determine if noise-related changes in speech processing are more prominent in lower relative to higher levels of the auditory pathway (brainstem vs. cerebral cortex). Distinguishing how adverse acoustics affect the neural basis of speech perception will offer immediate impact for the design of hearing aid and cochlear implant algorithms which could be correctly optimized to improve intelligibility in specific noise environments. These objective measures will also offer clinicians a new way to assess speech-related function in patients who cannot participate in behavioral speech assessment.

Erin G. Piker, AuD, PhD
Vestibulo-ocular Reflex and Functional Balance Correlates of Aging

Dizziness and/or unsteadiness are the 3rd most common complaints seen in primary care clinics with an overall incidence of 5-10%. The prevalence of these symptoms increases with increasing age, as does the risk of falling and injury. It is understood that dizziness is not a normal result of aging, but rather the result of pathophysiologic changes that may involve the vestibular system. While several investigators report demonstrable effects of age on quantitative tests measuring the vestibular system, others report no age effect. Given the discrepancies in the literature, for elderly patients it is often unclear whether minor alterations on vestibular test findings should be considered pathological and contributors to complaints of dizziness, or whether they are an age-related variant with minimal functional significance. Further, the connection between age-related changes on quantitative vestibular testing and the increased incidence of dizziness and falls in the elderly is unknown. The purpose of this proposed research is to better understand the effects of aging on the VOR using both sinusoidal harmonic acceleration and video head impulse testing and to determine any correlates between the VOR and both static and dynamic gait measures in an elderly population.

Rebecca M. Lewis, AuD Student and PhD Candidate
Concentration-Dependent Effects of Bone Morphogenetic Proteins on
Atoh1 Expression During Avian Hair Cell Regeneration

While humans endure permanent hearing loss after cochlear hair cell damage, birds regenerate hair cells and restore their hearing. Atoh1 is a transcription factor that is necessary and sufficient for hair cell differentiation during development, but does not seem to be sufficient for hair cell differentiation during regeneration. Bone morphogenetic proteins (BMPs) are expressed in hair cells both during development and in adulthood, with its effects being concentration-dependent (or morphogenic). Treating damaged cultures with BMPs decreases expression of Atoh1 and decreases hair cell differentiation, while treating damaged cultures with noggin (a BMP inhibitor) leads to opposing results. BMPs have a clear effect on Atoh1 and hair cell differentiation, but because its effects are highly concentration-dependent, the exact morphogenic effects of BMPs on Atoh1 expression should be characterized. For this, the avian system provides a useful model to characterize regenerative processes. Treatment factors of interest are those expressed in hair cells (BMP2 and BMP4) as well as their inhibitor noggin to determine the effect of treatment on Atoh1 transcription.

Spencer Smith, AuD/PhD Student
The Effect of Active Listening on Cochlear Mechanics in Children

Speech-in-noise perception is often impaired in children with auditory processing disorder (APD), a condition that impacts academic achievement. APD may arise from physiologic hypofunction of the efferent auditory system, which is believed to fine-tune the afferent pathway during active listening. One mechanism of the efferent auditory system is the medial olivocochlear (MOC) reflex of the low brainstem, which is thought to “unmask” transient signals in continuous noise by reflexively altering cochlear mechanics. This study investigates the extent to which the MOC reflex in normal hearing children, ages 8-12 years, is modulated by corticofugal projections engaged during active listening. An innovative Auditory Stroop Task will be presented to one ear while TEOAEs are recorded in the opposite ear. The Auditory Stroop Task is comprised of single-syllable words with specific gender meanings (e.g., king vs. queen, mom vs. dad) spoken by male or female voices. Listeners must identify either the gender of the talker (easy condition) or the gender meaning of the word (hard condition). We hypothesize that active listening to speech in noise will modulate the MOC reflex via corticofugal projections in a graded manner such that TEOAE suppression will increase with increased task difficulty.

Jessie N. Patterson, AuD/PhD Student
Characterizing Effects of Fatigue Following Physical Exertion
on Dynamic Visual Acuity Test in Collegiate Athletes

The necessity for including more objective concussion assessment measures has increased over the past decade. Currently, concussion diagnostic recommendations include postural control measures to examine balance function; however, these do not provide information regarding the functional use of the vestibular system. Additionally, these measures are affected by fatigue and evidence suggests that athletes should rest for approximately 20 minutes prior to evaluation. This is not feasible for healthcare professionals who need to make quick return to play decisions. Dynamic Visual Acuity Test (DVAT) provides information regarding the functional use of the vestibular system (vesitbulo-ocular reflex); therefore, DVAT may be beneficial for concussion assessment. Initially, this study will characterize the effects of fatigue on DVAT. We hypothesize that physical exertion will not have an effect on DVAT, thus allowing for an immediate objective tool for concussion assessment. UNL Athletes will be recruited and placed in either a control group or a physical exertion group. Both groups will perform DVAT at three time points: baseline (pre-test) and twice following either 20-minutes of rest (control group) or 20-minutes of physical exertion (physical exertion group). Multiple variance tests will be used to compare DVAT within the groups and between the groups.

Chrisanda Sanchez, AuD Student
Tablet Audiometry: Accurate Enough for Clinical Use?

New and emerging technology has provided audiologists with improved tools for clinical assessment and patient care. The increasing availability of and easy access to portable tablets and applications targeted to health care professionals has provided new opportunities to use alternate resources to measure patient hearing loss and deliver appropriate patient treatment. These portable applications have the potential to access patients in remote and rural settings, who would normally be unable to receive standard audiological care. Portable tablet-based applications could prove to be extremely beneficial in cases where portable audiometry is the only possible mode of testing. With the ease, portability, and convenience of using a tablet, this advancement in technology could change the mode of delivering patient care where access to sound treated booths is unavailable. However, it is critical that reliability and accuracy be assessed. Minimizing background noise and selecting appropriate transducers will influence threshold accuracy. Here, we will control background sound level and headphone selection during application based testing, and we will compare measured thresholds to those measured in a sound-booth with a professionally calibrated audiometer.

Kaitlyn Kennedy, AuD Student
Further Developing the Auditory Nerve Overlapped Waveform (ANOW)
as an Objective Measure of Low-Frequency Hearing

Current efforts in our laboratory aim to understand how attributes of low-frequency hearing, and hearing loss, can be objectively quantified with the new Auditory Nerve Overlapped Waveform (ANOW) developed by Lichtenhan et al. (2013). The ANOW is helpful because currently available otoacoustic emissions, auditory brainstem responses, and auditory steady state responses do not perform adequately because they require an ~20 dB correction factor for threshold estimation at low frequencies where speech vowels, environmental noise, and background noise occur.

Low-frequency tones between approximately 300 and 700 Hz are used to elicit ANOW. A natural presumption is that ANOW originates from afferent auditory-nerve-fibers in the low-frequency cochlear apex. However, when sound pressure is raised to measure ears with low-frequency hearing loss, one alternate possibility is that ANOW originates from distortion in the cochlear microphonic (CM) of outer hair cells in the high-frequency cochlear base. This project proposes to lead the efforts to develop a non-invasive technique that can distinguish between legitimate neural-originated ANOW and hair-cell originated CM.

Diana K. Weissbeck, AuD Student
Development of a Head Shake Postural Control Protocol
for Potential Use in Concussion Assessment

Approximately 30% of all high school and collegiate football players sustaining concussion return to play (RTP) on the day of their injury.[2] Postural stability is a valuable objective and quantifiable measure that can be used to support RTP decisions.[1] Maintaining postural control requires the integration of input from the visual, somatosensory, and vestibular systems[3,5]; impairment to any of the three sensory systems may cause an athlete to use inappropriate sensory cues to correct their motor responses in a perceived altered environment, thus predisposing them to further injury.[3] The development of sideline assessment tools, like the Balance Error Scoring System (BESS), has been a valuable way to provide immediate postural control measures. The BESS can be used to observe increased error scores (subjective observation) that may indicate residual symptoms from the injury.[6] Testing involves three different stances (double, single, and tandem) completed once on a firm and foam surface, for a total of six trials, 20 seconds each.[1] The Stability Evaluation Test (SET) is force plate tool that quantifies center of gravity (COG) composite scores under the same stance parameters as BESS. Though both methods are time-efficient and cost-effective, preliminary data by Honaker, Criter, and Patterson (in progress) demonstrates frequent ceiling effects on the double leg stance, as well as frequent floor effects on the single leg and tandem stances. Indeed, modification to the recommended concussion postural control measures is essential to eliminate these floor and ceiling effects. Addition of a head movement during the standing balance task may be a means of eradicating these effects. By stimulating the peripheral vestibular system with a horizontal and vertical head movement, the ceiling and floor effects established in the standard postural control measures may be eliminated, initiating a means of documenting decrements in postural control post-concussion. The addition of dynamic head movements to the postural control task may also challenge the participant by simultaneously provoking the peripheral vestibular system while upholding the stance, requiring the brain to differentiate body sway and head shake (HS) stimuli to maintain balance. A first step in determining the clinical utility of this protocol is to develop and test the protocol in healthy athlete controls. Thus, the central hypothesis of this proposal is that healthy athletes will be able to accurately perform the HS postural control assessment, with minimal COG sway.

1. Guskiewicz, K.M. (2001). Postural stability assessment following concussion: one piece of the puzzle. CJSM, 11, 182-189. 2. Guskiewicz, K.M., Bruce, S.L., Cantu, R.C., Ferrara, M.S., Kelly, J.P., McCrea, M., Putukian, M., & Valovich McLeod, T.C. (2004). National athletic trainers’ association position statement: management of sport-related concussion. JAT, 39(3), 280-297. 3. Guskiewicz, K.M. (2011). Balance assessment in the management of sport-related concussion. CJSM, 30, 89-102. 4. Honaker, J.A., Criter, R.E. & Patterson, J. (in progress). Effects of concussion on balance performance in collegiate sports. 5. Pang, M.Y.C., Lam, F.M., Wong, G.H., Au, I.H., & Chow, D. (2010). Balance performance in head-shake computerized dynamic posturography: aging effects and test-retest reliability. PTJ. 91, 246-253. 6. Susco, T.M., Valovich McLeod, W.C., Gansneder, B.M., & Shultz, S.J. (2004). Balance recovers within 20 minutes after exertion as measured by the balance error scoring system. JAT, 39(3), 241-246.

Reaghan Albert, BS
cVEMP Measures in Adolescents

cVEMPs in both seated with head turned supine with head lifted conditions were measured in 20 adolescents. cVEMP parameters were analyzed for age and neck length effects. A significant relationship between the P1 latency and neck length was found. Additionally, a significant difference in amplitude asymmetry ratios was found between measurement conditions. Structural variances in adolescents should be considered during VEMP testing. Additionally, bilateral cVEMP recording without the use of an EMG control is efficacious in this population.

Vijayalakshmi Easwar, MSc
Speech-evoked Envelope Following Responses
as an Objective Aided Outcome Measure

Objective outcome measures using auditory evoked potentials have the potential to improve evaluation of hearing aid fittings in young infants. The presentation will focus on development and evaluation of a test paradigm based on speech-evoked envelope following responses for use as an aided outcome measure. The study presents data from normal hearing and hearing impaired adults that support sensitivity of the test paradigm to changes in stimulus level, amplification and stimulus bandwidth that parallel performance in behavioral tests.

Jennifer Gonzalez, BA
Onset-Offset N1-P2 Response Comparisons:
A Possible Index for Tinnitus Verification

Our investigation with the onset-offset N1-P2 response for long duration broadband stimuli has yielded preliminary information that shows a distinct compromise of a monaural/binaural differential between onset and offset evoked potentials in normal hearing subjects with tinnitus. Normal hearing control subjects do not show these differences between monaural and binaural amplitudes which is computed for onset and offset responses. An index has been developed to readily show these key evoked potential differences.

Sarah Laurello, BA
Attitudes of Audiologists Toward Individuals with Multiple Disabilities

The purposes of the study were to determine if attitudes of audiologists toward working with individuals with multiple disabilities were consistent with normative data from the Interaction with Disabled Persons Scale (IDP) and to determine which within-subject factors predicted the largest differences in scores. Overall mean IDP  score was within one standard deviation of the normative sample mean IDP score. The most influential factors in predicting IDP scores were identified as job setting, age, level of contact, and academic degree.

Laura Street, MA
Proliferation Patterns in Zebrafish Neuromasts
Following Cisplatin Toxicity

Supporting cell proliferation patterns were assessed in the three most posterior neuromasts of zebrafish larvae following treatment with 1000 uM cisplatin. Proliferation was increased 48-72 hours post-exposure, but survival of internal supporting cell progeny was low three days after treatment. Since internal supporting cells divide and differentiate to replace lost hair cells, these results can account for why hair cell regeneration is impaired post-cisplatin administration. Additional research is required to uncover the limitations of potential hair cell regeneration therapies.

Sarah Obarowski
Optimization of FSP and HDCIS: Influence on Speech Perception

There are two coding strategies offered by MED-EL: Fine Structure Processing (FSP) and High Definition Continuous Interleaved Sampling (HDCIS). The aim of the FSP coding strategy is to provide both fine structure and amplitude information while HDCIS provides amplitude information alone. There has been no comparison of patients listening exclusively with one strategy after initial activation. The purpose of this study was to compare speech perception and music appreciation during the first six-months of listening experience with either FSP or HDCIS.

Brandon Fluegel
Neurophysiological Indicators of Early-Stage Cognitive Decline

Hearing status is predictive of cognitive status; it has been suggested that biomarkers for cognitive decline may exist within auditory neurophysiology. Neurophysiological differences between cognitively normal adults (CNOA) and individuals with mild cognitive impairment (MCI) were examined using auditory event-related potentials (ERPs) elicited by both speech and pure tone stimuli. The data received clear stimulus-related effects that interacted with group and suggested P2 amplitude at front-central electrodes and N1 amplitude at frontal electrodes as potential biomarkers of cognitive degeneration.

Karla Quinones, BS
Mechanisms Underlying Short-Term Synaptic Plasticity
in the Auditory Brainstem

Short-term synaptic plasticity is a neuronal task associated with simple learning and information processing. In the auditory brainstem synaptic depression is a form of short-term plasticity important for sound processing. Here we found both pre- and postsynaptic mechanism that contribute to synaptic depression. Factors include the time course and probability of presynaptic neurotransmitter release as well as the desensitization of postsynaptic receptors. These mechanisms which contribute to low-pass filtering are thought to be essential for the temporal encoding of sound.

Lindsey Rentmeester, AuD
Objective Measures of Fatigue in Children with and Without Hearing Loss

Anecdotal evidence suggests that children with hearing loss are at increased risk for fatigue. Increased reports of subjective fatigue in individuals with hearing loss may be due to increased mental effort required to process auditory information resulting in fewer resources available for other tasks. Fatigue measures were collected from six to twelve year old children with normal hearing and children with hearing over the course of a visit requiring sustained listening effort and attention.

Sarah Hayes
Noise-induced Hearing Loss Alters Hypothalamic-Pituitary-Adrenal Axis Activity in Rats

Ian Mertes
Repeatability and Stability of Medial Olivocochlear Reflex Effects on Short- and Long-latency Transient-evoked Otoacoustic Emissions

Measurement of the medial olivocochlear reflex (MOCR) using otoacoustic emissions (OAEs) may have clinical applications, such as predicting susceptibility to noise-induced hearing loss. A clinically useful test must identify statistically significant effects in individuals and must yield repeatable results in a normal population. Methods for detecting significant MOCR effects in individuals using transient-evoked (TE) OAEs were recently reported (Goodman et al., 2013, JARO). We extended the application of these methods to examine MOCR effects in individual subjects in terms of repeatability (presence/absence of statistical significance across tests) and stability (variation in magnitude and phase across tests). Recent studies have demonstrated that TEOAEs contain short- and long-latency components. Previous work has not examined MOCR effects on short-latency components. Therefore, a secondary purpose was to compare MOCR effects on short- and long-latency components.

Alexandra Parbery-Clark
Musical Experience and Hearing Loss:
Perceptual, Cognitive and Neural Benefits

With age, understanding speech - especially in noisy environments, becomes more difficult. Findings from several research groups have recently showed that older adult musicians both with normal hearing and hearing loss have perceptual advantages for hearing in noise that are underscored by enhanced cognitive and neural speech-sound processing relative to age- and hearing- matched controls. While these findings highlight the positive effects of musical training for both normal-hearing and hearing-impaired older adults, musical experience is rarely considered in a clinical setting. Given that a musician’s occupation puts him or her at risk for hearing loss, understanding how musicianship in a hearing-impaired population promotes hearing abilities relative to normal-hearing nonmusicians may improve clinical services to this population. Additionally, determining whether musical experience minimizes the effects of hearing loss on biological, perceptual and cognitive processes would further support the use of music as a rehabilitative tool for individuals with hearing loss.


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