Removal of physiological artifacts from simultaneous EEG and fMRI recordings.

OBJECTIVE: Simultaneous recording of the electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) allows a combination of eletrophysiological and haemodynamic information to be used to form a more complete picture of cerebral dynamics. However, EEG recorded within the MRI scanner is contaminated by both imaging artifacts and physiological artifacts. The majority of the techniques used to pre-process such EEG focus on removal of the imaging and balistocardiogram artifacts, with some success, but don't remove all other physiological artifacts. METHODS: We propose a new offline EEG artifact removal method based upon a combination of independent component analysis and fMRI-based head movement estimation to aid the removal of physiological artifacts from EEG recorded during EEG-fMRI recordings. Our method makes novel use of head movement trajectories estimated from the fMRI recording in order to assist with identifying physiological artifacts in the EEG and is designed to be used after removal of the fMRI imaging artifact from the EEG. RESULTS: We evaluate our method on EEG recorded during a joint EEG-fMRI session from healthy adult participants. Our method significantly reduces the influence of all types of physiological artifacts on the EEG. We also compare our method with a state-of-the-art physiological artifact removal method and demonstrate superior performance removing physiological artifacts. CONCLUSIONS: Our proposed method is able to remove significantly more physiological artifact components from the EEG, recorded during a joint EEG-fMRI session, than other state-of-the-art methods. SIGNIFICANCE: Our proposed method represents a marked improvement over current processing pipelines for removing physiological noise from EEG recorded during a joint EEG-fMRI session.

Test-retest reliability of tone- and 40 Hz train-evoked gamma oscillations in female rats and their sensitivity to low-dose NMDA channel blockade.

RATIONALE: Schizophrenia patients consistently show deficits in sensory-evoked broadband gamma oscillations and click-evoked entrainment at 40 Hz, called the 40-Hz auditory steady-state response (ASSR). Since such evoked oscillations depend on cortical N-methyl D-aspartic acid (NMDA)-mediated network activity, they can serve as pharmacodynamic biomarkers in the preclinical and clinical development of drug candidates engaging these circuits. However, there are few test-retest reliability data in preclinical species, a prerequisite for within-subject testing paradigms. OBJECTIVE: We investigated the long-term psychometric stability of these measures in a rodent model. METHODS: Female rats with chronic epidural implants were used to record tone- and 40 Hz click-evoked responses at multiple time points and across six sessions, spread over 3 weeks. We assessed reliability using intraclass correlation coefficients (ICC). Separately, we used mixed-effects ANOVA to examine time and session effects. Individual subject variability was determined using the coefficient of variation (CV). Lastly, to illustrate the importance of long-term measure stability for within-subject testing design, we used low to moderate doses of an NMDA antagonist MK801 (0.025-0.15 mg/kg) to disrupt the evoked response. RESULTS: We found that 40-Hz ASSR showed good reliability (ICC=0.60-0.75), while the reliability of tone-evoked gamma ranged from poor to good (0.33-0.67). We noted time but no session effects. Subjects showed a lower variance for ASSR over tone-evoked gamma. Both measures were dose-dependently attenuated by NMDA antagonism. CONCLUSION: Overall, while both evoked gamma measures use NMDA transmission, 40-Hz ASSR showed superior psychometric properties of higher ICC and lower CV, relative to tone-evoked gamma.

Distributed source modeling of intracranial stereoelectro-encephalographic measurements.

Intracranial stereoelectroencephalography (sEEG) provides unsurpassed sensitivity and specificity for human neurophysiology. However, functional mapping of brain functions has been limited because the implantations have sparse coverage and differ greatly across individuals. Here, we developed a distributed, anatomically realistic sEEG source-modeling approach for within- and between-subject analyses. In addition to intracranial event-related potentials (iERP), we estimated the sources of high broadband gamma activity (HBBG), a putative correlate of local neural firing. Our novel approach accounted for a significant portion of the variance of the sEEG measurements in leave-one-out cross-validation. After logarithmic transformations, the sensitivity and signal-to-noise ratio were linearly inversely related to the minimal distance between the brain location and electrode contacts (slope≈-3.6). The signa-to-noise ratio and sensitivity in the thalamus and brain stem were comparable to those locations at the vicinity of electrode contact implantation. The HGGB source estimates were remarkably consistent with analyses of intracranial-contact data. In conclusion, distributed sEEG source modeling provides a powerful neuroimaging tool, which facilitates anatomically-normalized functional mapping of human brain using both iERP and HBBG data.

Auditory Mapping With MEG: An Update on the Current State of Clinical Research and Practice With Considerations for Clinical Practice Guidelines.

Auditory evoked fields (AEFs) are well suited for studies of auditory processing in patients. Their sources have been localized to Heschl's gyri and to the supratemporal auditory cortices. Auditory evoked fields are known to be modulated by peripheral and central lesions of auditory pathways and to reflect group-level pathophysiology of neurodevelopmental and psychiatric disorders. They are useful in lateralization of language processes for planning neurosurgery and for localization of language-related cortex. The recently developed artifact rejection and movement compensation methods will enhance and extend the use of AEFs in studies of clinical patients and pediatric groups. New pediatric magnetoencephalography systems will facilitate clinical AEF studies of developmental disorders. In addition to their established use in planning neurosurgery, AEF findings in several new clinical patient groups suffering, e.g., from developmental, neurodegenerative, or psychiatric disorders have been reported. Several recent investigations report the correlations with clinical symptoms and sensitivity and specificity profiles of AEFs in studies of these disorders; this development is mandatory in gaining wider clinical approval for the use of AEFs in clinical practice dealing with individual patients. Most promising future research lines of clinical applicability of AEFs focus on developmental and psychiatric disorders.

Reliability of mismatch negativity event-related potentials in a multisite, traveling subjects study.

OBJECTIVE: To determine the optimal methods for measuring mismatch negativity (MMN), an auditory event-related potential (ERP), and quantify sources of MMN variance in a multisite setting. METHODS: Reliability of frequency, duration, and double (frequency + duration) MMN was determined from eight traveling subjects, tested on two occasions at eight laboratory sites. Deviant-specific variance components were estimated for MMN peak amplitude and latency measures using different ERP processing methods. Generalizability (G) coefficients were calculated using two-facet (site and occasion), fully-crossed models and single-facet (occasion) models within each laboratory to assess MMN reliability. RESULTS: G-coefficients calculated from two-facet models indicated fair (0.4 < G<=0.6) duration MMN reliability at electrode Fz, but poor (G < 0.4) double and frequency MMN reliability. Single-facet G-coefficients averaged across laboratory resulted in improved reliability (G > 0.5). MMN amplitude reliability was greater than latency reliability, and reliability with mastoid referencing significantly outperformed nose-referencing. CONCLUSIONS: EEG preprocessing methods have an impact on the reliability of MMN amplitude. Within site MMN reliability can be excellent, consistent with prior single site studies. SIGNIFICANCE: With standardized data collection and ERP processing, MMN can be reliably obtained in multisite studies, providing larger samples sizeswithin rare patient groups.

Relationship between hearing capacity and performance on tasks of speech perception in children with hearing loss. / Relações entre medidas de capacidade auditiva e desempenho em tarefas de percepção da fala em crianças com deficiência auditiva.

PURPOSE: To establish the relationship between the performance on word recognition tasks, using words with and without sense and degree, and the configuration of hearing loss, by using Speech Inteligibility Index (SII) values as indicators, in children with hearing loss. METHODS: SII were established for 55 and 65 Decibel of Sound Pressure Level (dB SPL) input sounds of ten children presenting bilateral sensorineural hearing loss (SNHL), adapted with bilateral hearing aids, and who have oral language as the main mode of communication. The children were submitted to a word and nonsense-word repetition task of two or three intensity degrees. Their productions were analyzed according to the Word Association for Syllable Perception (WASP) Protocol. In the data analysis, the values of SII were compared with the results obtained in each analysis criterion. RESULTS: Pertaining to the words, there was statistically significant difference between the two types of stimuli in 55 dBSPL. As for the performance of consonants and point of articulation, there was a statistically significant difference between stimuli types in 65 and 55 dB SPL, and between intensities 65 and 55 dB SPL in nonsense words. CONCLUSION: Overall, there was no regularity in the relationship between hearing ability and performance in speech perception tasks. The results suggest that performance in the nonsense words recognition tasks was more related to intelligibility index than to words with meaning, possibly because it limits semantic closure strategies by the subject.

OBJETIVO: Estabelecer relações entre o desempenho em tarefa de reconhecimento de palavras com e sem sentido e grau e configuração da perda auditiva, utilizando valores de Índices de Inteligibilidade de Fala (SII) como indicadores, em crianças com deficiência auditiva. MÉTODO: Foram estabelecidos os SII para sons de entradas de 55 e 65 Decibéis Nível de Pressão Sonora (dBNPS) de dez crianças com perda auditiva neurossensorial usuárias de aparelho de amplificação sonora individual bilateralmente que têm a linguagem oral como principal modalidade de comunicação. As crianças foram submetidas à tarefa de repetição de palavras com e sem sentido em duas ou três diferentes intensidades. As emissões foram analisadas de acordo com o Protocolo Word Association for Syllable Perception (WASP). Na análise dos dados, o SII foi comparado com os resultados obtidos em cada critério de análise. RESULTADOS: Para o desempenho em palavras, houve diferença estatisticamente significante entre os dois tipos de estímulo em 55dBNPS. Para o desempenho em consoantes e ponto de articulação, houve diferença estatisticamente significante entre os tipos de estímulos em 65 e 55dBNPS e também entre as intensidades de 65 e 55 dBNPS nas palavras sem sentido. CONCLUSÃO: De modo geral, não houve regularidade na relação entre capacidade auditiva e desempenho em tarefas de percepção da fala. Os resultados sugerem que o desempenho nas tarefas de reconhecimento de palavras sem sentido tem maior relação com o índice de inteligibilidade do que as palavras com sentido, possivelmente por limitar as estratégias de fechamento semântico pelo sujeito.

Relações entre medidas de capacidade auditiva e desempenho em tarefas de percepção da fala em crianças com deficiência auditiva / Relationship between hearing capacity and performance on tasks of speech perception in children with hearing loss

RESUMO Objetivo Estabelecer relações entre o desempenho em tarefa de reconhecimento de palavras com e sem sentido e grau e configuração da perda auditiva, utilizando valores de Índices de Inteligibilidade de Fala (SII) como indicadores, em crianças com deficiência auditiva. Método Foram estabelecidos os SII para sons de entradas de 55 e 65 Decibéis Nível de Pressão Sonora (dBNPS) de dez crianças com perda auditiva neurossensorial usuárias de aparelho de amplificação sonora individual bilateralmente que têm a linguagem oral como principal modalidade de comunicação. As crianças foram submetidas à tarefa de repetição de palavras com e sem sentido em duas ou três diferentes intensidades. As emissões foram analisadas de acordo com o Protocolo Word Association for Syllable Perception (WASP). Na análise dos dados, o SII foi comparado com os resultados obtidos em cada critério de análise. Resultados Para o desempenho em palavras, houve diferença estatisticamente significante entre os dois tipos de estímulo em 55dBNPS. Para o desempenho em consoantes e ponto de articulação, houve diferença estatisticamente significante entre os tipos de estímulos em 65 e 55dBNPS e também entre as intensidades de 65 e 55 dBNPS nas palavras sem sentido. Conclusão De modo geral, não houve regularidade na relação entre capacidade auditiva e desempenho em tarefas de percepção da fala. Os resultados sugerem que o desempenho nas tarefas de reconhecimento de palavras sem sentido tem maior relação com o índice de inteligibilidade do que as palavras com sentido, possivelmente por limitar as estratégias de fechamento semântico pelo sujeito.

ABSTRACT Purpose To establish the relationship between the performance on word recognition tasks, using words with and without sense and degree, and the configuration of hearing loss, by using Speech Inteligibility Index (SII) values as indicators, in children with hearing loss. Methods SII were established for 55 and 65 Decibel of Sound Pressure Level (dB SPL) input sounds of ten children presenting bilateral sensorineural hearing loss (SNHL), adapted with bilateral hearing aids, and who have oral language as the main mode of communication. The children were submitted to a word and nonsense-word repetition task of two or three intensity degrees. Their productions were analyzed according to the Word Association for Syllable Perception (WASP) Protocol. In the data analysis, the values of SII were compared with the results obtained in each analysis criterion. Results Pertaining to the words, there was statistically significant difference between the two types of stimuli in 55 dBSPL. As for the performance of consonants and point of articulation, there was a statistically significant difference between stimuli types in 65 and 55 dB SPL, and between intensities 65 and 55 dB SPL in nonsense words. Conclusion Overall, there was no regularity in the relationship between hearing ability and performance in speech perception tasks. The results suggest that performance in the nonsense words recognition tasks was more related to intelligibility index than to words with meaning, possibly because it limits semantic closure strategies by the subject.

Generalizability of clinically measured acoustic reflexes to brief sounds.

Middle ear muscle contractions (MEMC) can be elicited in response to high-level sounds, and have been used clinically as acoustic reflexes (ARs) during evaluations of auditory system integrity. The results of clinical AR evaluations do not necessarily generalize to different signal types or durations. The purpose of this study was to evaluate the likelihood of observing MEMC in response to brief sound stimuli (tones, recorded gunshots, noise) in adult participants (N = 190) exhibiting clinical ARs and excellent hearing sensitivity. Results revealed that the presence of clinical ARs was not a sufficient indication that listeners will also exhibit MEMC for brief sounds. Detection rates varied across stimulus types between approximately 20% and 80%. Probabilities of observing MEMC also differed by clinical AR magnitude and latency, and declined over the period of minutes during the course of the MEMC measurement series. These results provide no support for the inclusion of MEMC as a protective factor in damage-risk criteria for impulsive noises, and the limited predictability of whether a given individual will exhibit MEMC in response to a brief sound indicates a need to measure and control for MEMC in studies evaluating pharmaceutical interventions for hearing loss.

Variable-rate frequency sweeps and their application to the measurement of otoacoustic emissions.

Swept tones allow the efficient measurement of otoacoustic emissions (OAEs) with fine frequency resolution. Although previous studies have explored the influence of different sweep parameters on the measured OAE, none have directly considered their effects on the measurement noise floor. The present study demonstrates that parameters such as sweep type (e.g., linear or logarithmic), sweep rate, and analysis bandwidth affect the measurement noise and can be manipulated to control the noise floor in individual subjects. Although responses to discrete-tone stimuli can be averaged until the uncertainty of the measurement meets a specified criterion at each frequency, linear or logarithmic sweeps offer no such flexibility. However, measurements of the power spectral density of the ambient noise can be used to construct variable-rate sweeps that yield a prescribed (e.g., constant) noise floor across frequency; in effect, they implement a form of frequency-dependent averaging. The use of noise-compensating frequency sweeps is illustrated by the measurement of distortion-product OAEs at low frequencies, where the ear-canal noise is known to vary significantly.

A comparison of ear-canal-reflectance measurement methods in an ear simulator.

Ear-canal reflectance has been researched extensively for diagnosing conductive hearing disorders and compensating for the ear-canal acoustics in non-invasive measurements of the auditory system. Little emphasis, however, has been placed on assessing measurement accuracy and variability. In this paper, a number of ear-canal-reflectance measurement methods reported in the literature are utilized and compared. Measurement variation seems to arise chiefly from three factors: the residual ear-canal length, the ear-probe insertion angle, and the measurement frequency bandwidth. Calculation of the ear-canal reflectance from the measured ear-canal impedance requires estimating the ear-canal characteristic impedance in situ. The variability in ear-canal estimated characteristic impedance and reflectance due to these principal factors is assessed in an idealized controlled setup using a uniform occluded-ear simulator. In addition, the influence of this measurement variability on reflectance-based methods for calibrating stimulus levels is evaluated and, by operating the condenser microphone of the occluded-ear simulator as an electro-static speaker, the variability in estimating the emitted pressure from the ear is determined. The various measurement methods differ widely in their robustness to variations in the three principal factors influencing the accuracy and variability of ear-canal reflectance.

On the calculation of reflectance in non-uniform ear canals.

Ear-canal reflectance is useful for quantifying the conductive status of the middle ear because it can be measured non-invasively at a distance from the tympanic membrane. Deriving the ear-canal reflectance requires decomposing the total acoustic pressure into its forward- and reverse-propagating components. This decomposition is conveniently achieved using formulas that involve the input and characteristic impedances of the ear canal. The characteristic impedance is defined as the ratio of sound pressure to volume flow of a propagating wave and, for uniform waveguides, the plane-wave characteristic impedance is a real-valued constant. However, in non-uniform waveguides, the characteristic impedances are complex-valued quantities, depend on the direction of propagation, and more accurately characterize a propagating wave in a non-uniform ear canal. In this paper, relevant properties of the plane-wave and spherical-wave characteristic impedances are reviewed. In addition, the utility of the plane-wave and spherical-wave reflectances in representing the reflection occurring due to the middle ear, calibrating stimulus levels, and characterizing the emitted pressure in simulated non-uniform ear canals is investigated and compared.

Development of an automatic classifier for the prediction of hearing impairment from industrial noise exposure.

The ISO-1999 [(2013). International Organization for Standardization, Geneva, Switzerland] standard is the most commonly used approach for estimating noise-induced hearing trauma. However, its insensitivity to noise characteristics limits its practical application. In this study, an automatic classification method using the support vector machine (SVM) was developed to predict hearing impairment in workers exposed to both Gaussian (G) and non-Gaussian (non-G) industrial noises. A recently collected human database (N = 2,110) from industrial workers in China was used in the present study. A statistical metric, kurtosis, was used to characterize the industrial noise. In addition to using all the data as one group, the data were also broken down into the following four subgroups based on the level of kurtosis: G/quasi-G, low-kurtosis, middle-kurtosis, and high-kurtosis groups. The performance of the ISO-1999 and the SVM models was compared over these five groups. The results showed that: (1) The performance of the SVM model significantly outperformed the ISO-1999 model in all five groups. (2) The ISO-1999 model could not properly predict hearing impairment for the high-kurtosis group. Moreover, the ISO-1999 model is likely to underestimate hearing impairment caused by both G and non-G noise exposures. (3) The SVM model is a potential tool to predict hearing impairment caused by diverse noise exposures.

Elevated physiological arousal is associated with larger but more variable neural responses to small acoustic change in children during a passive auditory attention task.

Little is known of how autonomic arousal relates to neural responsiveness during auditory attention. We presented N = 21 5-7-year-old children with an oddball auditory mismatch paradigm, whilst concurrently measuring heart rate fluctuations. Children with higher mean autonomic arousal, as indexed by higher heart rate (HR) and decreased high-frequency (0.15-0.8 Hz) variability in HR, showed smaller amplitude N250 responses to frequently presented (70%), 500 Hz standard tones. Follow-up analyses showed that the modal evoked response was in fact similar, but accompanied by more large and small amplitude responses and greater variability in peak latency in the high HR group, causing lower averaged responses. Similar patterns were also observed when examining heart rate fluctuations within a testing session, in an analysis that controlled for between-participant differences in mean HR. In addition, we observed larger P150/P3a amplitudes in response to small acoustic contrasts (750 Hz tones) in the high HR group. Responses to large acoustic contrasts (bursts of white noise), however, evoked strong early P3a phase in all children and did not differ by high/low HR. Our findings suggest that elevated physiological arousal may be associated with high variability in auditory ERP responses in young children, along with increased responsiveness to small acoustic changes.

COMPARISON OF HEARING THRESHOLD ESTIMATION USING AUDITORY STEADY STATE RESPONSES AND BRAINSTEM AUDITORY EVOKED POTENTIALS IN CHILDREN.

Current recommendations proposed by pediatric audiologists are to commence with hearing amplification in children aged 6 months and above, after previous determination of the type and degree of hearing impairment and audiometric configuration. The goal of this study was to compare results obtained by click-evoked auditory brainstem response (c-ABR) and auditory steady state response (ASSR) in a group of children. This study included 68 children with different degrees of hearing impairment evaluated by c-ABR and ASSR. It is well-known that the c-ABR threshold highly correlates with behavioral hearing level at 2 kHz. In our study, the correlation between the c-ABR and ASSR thresholds in the whole sample was 0.58, 0.73, 0.97, 0.96, 0.95, 0.97; in the group of children with c-ABR thresholds up to 40 dBHL, it was 0.42, 0.73, 0.86, 0.74, 0.81, 0.81; and in the group with c-ABR thresholds worse than 40 dBHL, it was 0.46, 0.56, 0.89, 0.83, 0.85, 0.89 at 0.5, 1, 2, 4, 1-4, 2-4 kHz, respectively. Individual differences between the c-ABR and ASSR thresholds in the whole sample were up to 95, 90, 20, 25 dB at 0.5, 1, 2, 4 kHz, respectively. Study results indicated that there was strong correlation between the c-ABR and ASSR thresholds at 2, 4, 1-4, 2-4 kHz. The ASSR can be used as a valuable clinical tool and an excellent complementary method which, along with other audiologic techniques, provides more accurate hearing threshold estimation at an early age in children.

Evanescent waves in simulated ear canals: Experimental demonstration and method for compensation.

Evanescent waves emerge from a small sound source that radiates into a waveguide with a larger cross-sectional area, but unlike planar waves, do not propagate far from the source. Evanescent waves thus contaminate in-ear calibration of acoustic stimuli. Measurements with an otoacoustic-emission (OAE) probe inserted at the entrance of long tubes of various diameters show a decline in the evanescent wave with distance from the source when advancing a probe tube through the OAE probe and into the long tube. The amplitude of the evanescent pressure increases with frequency and depends strongly on the diameter of the long tube. Modifying the shape of the aperture of the probe's sound source, thus effectively enlarging its diameter and redirecting acoustic flow, greatly reduced evanescent waves. The reduction in evanescent-wave pressure was observed in calibration cavities used to determine the Thévenin-equivalent source pressure and impedance of the probe. Errors in source calibrations were considerably larger in the unmodified configuration. An alternative method is proposed for calculation of acoustic source parameters that models the evanescent-wave pressure and reduces its influence on the calculation. This reduction greatly improves the quality of source calibrations, which should improve the accuracy of ear-canal impedance measurements and related quantities.

Performance evaluation of an active headrest considering non-stationary broadband disturbances and head movement.

An application of active noise control (ANC) is the active headrest, using actuators (loadspeakers), sensors (microphones), and a controller to create a local zone of quiet around the occupants head. In this paper, the attenuation performance of various ANC-algorithms for active headrests known from literature is evaluated considering non-stationary broadband disturbances and head movement. Numerical studies are performed to determine the optimal plant models and parameters for the ANC-algorithms. Based on the findings of the numerical studies, several real-time experiments are conducted with and without head tracking examining the distribution of the 10 dB zone of quiet and the attenuation at the occupants ear using either a head mounted microphone technique, the remote microphone technique, the virtual microphone technique, or the virtual microphone control method. It is found that none of the algorithms using a virtual sensing technique can produce a 10 dB zone of quiet for all considered non-stationary broadband disturbances and head movement. For the algorithm using a head mounted microphone, it is possible to form a 10 dB zone of quiet, but placing a microphone at the ear is not feasible in most situations.

Auditory Icon Alarms Are More Accurately and Quickly Identified than Current Standard Melodic Alarms in a Simulated Clinical Setting.

BACKGROUND: Current standard audible medical alarms are difficult to learn and distinguish from one another. Auditory icons represent a new type of alarm that has been shown to be easier to learn and identify in laboratory settings by lay subjects. In this study, we test the hypothesis that icon alarms are easier to learn and identify than standard alarms by anesthesia providers in a simulated clinical setting. METHODS: Twenty anesthesia providers were assigned to standard or icon groups. Experiments were conducted in a simulated intensive care unit. After a brief group-specific alarm orientation, subjects identified patient-associated alarm sounds during the simulation and logged responses via a tablet computer. Each subject participated in the simulation twice and was exposed to 32 alarm annunciations. Primary outcome measures were response accuracy and response times. Secondary outcomes included assessments of perceived fatigue and task load. RESULTS: Overall accuracy rate in the standard alarm group was 43% (mean) and in the icon group was 88% (mean). Subjects in the icon group were 26.1 (odds ratio [98.75% CI, 8.4 to 81.5; P < 0.001]) times more likely to correctly identify an alarm. Response times in the icon group were shorter than in the standard alarm group (12 vs. 15 s, difference 3 s [98.75% CI ,1 to 5; P < 0.001]). CONCLUSIONS: Under our simulated conditions, anesthesia providers more correctly and quickly identified icon alarms than standard alarms. Subjects were more likely to perceive higher fatigue and task load when using current standard alarms than icon alarms.

Down for the count: The critical endpoint in ototoxicity remains the cytocochleogram.

There are three major assays that must be conducted in standard investigational new drug (IND) -enabling ototoxicity study designs: 1) functional acoustic threshold measurements (Auditory Brainstem Respsonse, ABR); 2) otohistopathology and 3) cytocochleograms. We provide evidence to demonstrate the unreliability of auditory threshold shifts (ABRs) to predict cochlear cell death and build a case for conducting full cochlea processing and cell count measurements from the complete cochlea from apex to base.

The clinical use of Arthur Boothroyd (AB) word lists in Australia: exploring evidence-based practice.

OBJECTIVE: Limited empirical investigation exists validating the use of Arthur Boothroyd (AB) word recognition materials within the Australian clinical context. The current research was undertaken to examine the evidence base and clinical implementation/interpretation of AB words in Australia. DESIGN: An on-line 22-question survey was e-mailed to members of the peak audiology professional body in Australia. STUDY SAMPLE: Three hundred and twelve responses were recorded between April and June 2015 from audiologists of a range of ages, working in various clinical settings. RESULTS: The survey results suggested audiologists use AB words on a wide range of clients from children <5 to adults ≥80 years, for diverse purposes including diagnosis of retrocochlear pathology, candidacy and validation of rehabilitative options, and client counselling. A majority of respondents reported typically administering one or two word lists per ear, and over 99% of audiologists utilised phonemic scoring. There was no consensus regarding what constitutes a significant difference between any two given scores. CONCLUSIONS: Wide variation exists in the administration and interpretation of AB words in Australia. There appears to be a mismatch between clinical utilisation of AB words and existing evidence-based empirical data. Further research is required to improve evidence-based audiologist training, and thereby current clinical use of AB words.

Big Stimulus, Little Ears: Safety in Administering Vestibular-Evoked Myogenic Potentials in Children.

BACKGROUND: Cervical and ocular vestibular-evoked myogenic potentials (VEMPs) have become common clinical vestibular assessments. However, VEMP testing requires high intensity stimuli, raising concerns regarding safety with children, where sound pressure levels may be higher due to their smaller ear canal volumes. PURPOSE: The purpose of this study was to estimate the range of peak-to-peak equivalent sound pressure levels (peSPLs) in child and adult ears in response to high intensity stimuli (i.e., 100 dB normal hearing level [nHL]) commonly used for VEMP testing and make a determination of whether acoustic stimuli levels with VEMP testing are safe for use in children. RESEARCH DESIGN: Prospective experimental. STUDY SAMPLE: Ten children (4-6 years) and ten young adults (24-35 years) with normal hearing sensitivity and middle ear function participated in the study. DATA COLLECTION AND ANALYSIS: Probe microphone peSPL measurements of clicks and 500 Hz tonebursts (TBs) were recorded in tubes of small, medium, and large diameter, and in a Brüel & Kjær Ear Simulator Type 4157 to assess for linearity of the stimulus at high levels. The different diameter tubes were used to approximate the range of cross-sectional areas in infant, child, and adult ears, respectively. Equivalent ear canal volume and peSPL measurements were then recorded in child and adult ears. Lower intensity levels were used in the participant's ears to limit exposure to high intensity sound. The peSPL measurements in participant ears were extrapolated using predictions from linear mixed models to determine if equivalent ear canal volume significantly contributed to overall peSPL and to estimate the mean and 95% confidence intervals of peSPLs in child and adult ears when high intensity stimulus levels (100 dB nHL) are used for VEMP testing without exposing subjects to high-intensity stimuli. RESULTS: Measurements from the coupler and tubes suggested: 1) each stimuli was linear, 2) there were no distortions or nonlinearities at high levels, and 3) peSPL increased with decreased tube diameter. Measurements in participant ears suggested: 1) peSPL was approximately 3 dB larger in child compared to adult ears, and 2) peSPL was larger in response to clicks compared to 500 Hz TBs. The model predicted the following 95% confidence interval for a 100 dB nHL click: 127-136.5 dB peSPL in adult ears and 128.7-138.2 dB peSPL in child ears. The model predicted the following 95% confidence interval for a 100 dB nHL 500 Hz TB stimulus: 122.2-128.2 dB peSPL in adult ears and 124.8-130.8 dB peSPL in child ears. CONCLUSIONS: Our findings suggest that 1) when completing VEMP testing, the stimulus is approximately 3 dB higher in a child's ear, 2) a 500 Hz TB is recommended over a click as it has lower peSPL compared to the click, and 3) both duration and intensity should be considered when choosing VEMP stimuli. Calculating the total sound energy exposure for your chosen stimuli is recommended as it accounts for both duration and intensity. When using this calculation for children, consider adding 3 dB to the stimulus level.