Evidence for a dynorphin-mediated inner ear immune/inflammatory response and glutamate-induced neural excitotoxicity: an updated analysis.

Acoustic overstimulation (AOS) is defined as the stressful overexposure to high-intensity sounds. AOS is a precipitating factor that leads to a glutamate (GLU)-induced Type I auditory neural excitotoxicity and an activation of an immune/inflammatory/oxidative stress response within the inner ear, often resulting in cochlear hearing loss. The dendrites of the Type I auditory neural neurons that innervate the inner hair cells (IHCs), and respond to the IHC release of the excitatory neurotransmitter GLU, are themselves directly innervated by the dynorphin (DYN)-bearing axon terminals of the descending brain stem lateral olivocochlear (LOC) system. DYNs are known to increase GLU availability, potentiate GLU excitotoxicity, and induce superoxide production. DYNs also increase the production of proinflammatory cytokines by modulating immune/inflammatory signal transduction pathways. Evidence is provided supporting the possibility that the GLU-mediated Type I auditory neural dendritic swelling, inflammation, excitotoxicity, and cochlear hearing loss that follow AOS may be part of a brain stem-activated, DYN-mediated cascade of inflammatory events subsequent to a LOC release of DYNs into the cochlea. In support of a DYN-mediated cascade of events are established investigations linking DYNs to the immune/inflammatory/excitotoxic response in other neural systems.

Central deafness: a review of past and current perspectives.

Objective: The purpose of this review was to describe and differentiate clinical syndromes caused by lesions of the central auditory nervous system (CANS). Design: Relevant literature was identified through Pubmed and Google Scholar searches using the key terms: central deafness, auditory agnosia, word deafness and cortical deafness. Given the authors' intent to review past and current perspectives on central deafness, no publication date range was imposed. Study sample: The review is organised around complete central deafness (CCD), central deafness (CD), word deafness and nonverbal agnosia (NVA), including anatomy and pathophysiology, symptom profile and audiological findings. Four case studies are presented to demonstrate the clinical correlates of CD. Conclusions: Central deafness is a rare condition typically resulting from bilateral compromise of the CANS. The closer to the auditory cortex bilateral lesions are located, the greater the probability of CD. A variety of symptoms present with or appear subsequent to CD, including tinnitus, hallucinations, voice changes and hypersensitivity to sounds (if heard by the patient), as well as diverse neurological symptoms depending on the non-auditory areas of the brain that may also be involved. Thorough and appropriate audiological testing is critical to accurately diagnose CD and its variants.

Practical guidelines to minimise language and cognitive confounds in the diagnosis of CAPD: a brief tutorial.

OBJECTIVE: To provide audiologists with strategies to minimise confounding cognitive and language processing variables and accurately diagnose central auditory processing disorder (CAPD). DESIGN: Tutorial. STUDY SAMPLE: None. RESULTS: Strategies are reviewed to minimise confounding cognitive and language processing variables and accurately diagnose CAPD. CONCLUSIONS: Differential diagnosis is exceedingly important and can be quite challenging. Distinguishing between two or more conditions presenting with similar symptoms or attributes requires multidisciplinary, comprehensive assessment. To ensure appropriate interventions, the audiologist is a member of the multidisciplinary team responsible for determining whether there is an auditory component to other presenting deficits or whether one condition is responsible for the symptoms seen in another. Choice of tests should be guided both by the symptoms of the affected individual, as established in an in-depth interview and case history, the individual's age and primary language, and by the specific deficits reported to be associated with specific clinical presentations. Knowing which tests are available, their strengths and limitations, the processes assessed, task and response requirements, and the areas of the central auditory nervous system (CANS) to which each test is most sensitive provides the audiologist with critical information to assist in the differential diagnostic process.

Auditory Impairments in HIV-Infected Children.

OBJECTIVES: In a cross-sectional study of human immunodeficiency virus (HIV)-infected adults, the authors showed lower distortion product otoacoustic emissions (DPOAEs) in HIV+ individuals compared with controls as well as findings consistent with a central auditory processing deficit in HIV+ adults on antiretroviral therapy. The authors hypothesized that HIV+ children would also have a higher prevalence of abnormal central and peripheral hearing test results compared with HIV- controls. DESIGN: Pure-tone thresholds, DPOAEs, and tympanometry were performed on 244 subjects (131 HIV+ and 113 HIV- subjects). Thirty-five of the HIV+, and 3 of the HIV- subjects had a history of tuberculosis treatment. Gap detection results were available for 18 HIV- and 44 HIV+ children. Auditory brainstem response results were available for 72 HIV- and 72 HIV+ children. Data from ears with abnormal tympanograms were excluded. RESULTS: HIV+ subjects were significantly more likely to have abnormal tympanograms, histories of ear drainage, tuberculosis, or dizziness. All audiometric results were compared between groups using a two-way ANOVA with HIV status and ear drainage history as grouping variables. Mean audiometric thresholds, gap detection thresholds, and auditory brainstem response latencies did not differ between groups, although the HIV+ group had a higher proportion of individuals with a hearing loss >25 dB HL in the better ear. The HIV+ group had reduced DPOAE levels (p < 0.05) at multiple frequencies compared with HIV- subjects. No relationships were found between treatment regimens or delay in starting treatment and audiological parameters. CONCLUSIONS: As expected, children with HIV+ were more likely to have a history of ear drainage, and to have abnormal tympanograms. Similar to the adult findings, the HIV+ group did not show significantly reduced audiometric thresholds, but did have significantly lower DPOAE magnitudes. These data suggest that (1) HIV+ children often have middle ear damage which complicates understanding the direct effects of HIV on the hearing system, and (2) even when corrected for confounders DPOAEs were lower in the HIV+ group. Previous studies suggest ototoxicity from antiretroviral drugs is an unlikely cause of the reduced DPOAE magnitudes. Other possibilities include effects on efferent pathways connecting to outer hair cells or a direct effect of HIV on the cochlea.

Auditory impairments in HIV-infected individuals in Tanzania.

OBJECTIVES: Abnormal hearing tests have been noted in human immunodeficiency virus (HIV)-infected patients in several studies, but the nature of the hearing deficit has not been clearly defined. The authors performed a cross-sectional study of both HIV+ and HIV- individuals in Tanzania by using an audiological test battery. The authors hypothesized that HIV+ adults would have a higher prevalence of abnormal central and peripheral hearing test results compared with HIV- controls. In addition, they anticipated that the prevalence of abnormal hearing assessments would increase with antiretroviral therapy (ART) use and treatment for tuberculosis (TB). DESIGN: Pure-tone thresholds, distortion product otoacoustic emissions (DPOAEs), tympanometry, and a gap-detection test were performed using a laptop-based hearing testing system on 751 subjects (100 HIV- in the United States, plus 651 in Dar es Salaam, Tanzania, including 449 HIV+ [130 ART- and 319 ART+], and 202 HIV-, subjects. No U.S. subjects had a history of TB treatment. In Tanzania, 204 of the HIV+ and 23 of the HIV- subjects had a history of TB treatment. Subjects completed a video and audio questionnaire about their hearing, as well as a health history questionnaire. RESULTS: HIV+ subjects had reduced DPOAE levels compared with HIV- subjects, but their hearing thresholds, tympanometry results, and gap-detection thresholds were similar. Within the HIV+ group, those on ART reported significantly greater difficulties understanding speech in noise, and were significantly more likely to report that they had difficulty understanding speech than the ART- group. The ART+ group had a significantly higher mean gap-detection threshold compared with the ART- group. No effects of TB treatment were seen. CONCLUSIONS: The fact that the ART+/ART- groups did not differ in measures of peripheral hearing ability (DPOAEs, thresholds), or middle ear measures (tympanometry), but that the ART+ group had significantly more trouble understanding speech and had higher gap-detection thresholds indicates a central processing deficit. These data suggest that: (1) hearing deficits in HIV+ individuals could be a CNS side effect of HIV infection, (2) certain ART regimens might produce CNS side effects that manifest themselves as hearing difficulties, and/or (3) some ART regimens may treat CNS HIV inadequately, perhaps due to insufficient CNS drug levels, which is reflected as a central hearing deficit. Monitoring of central hearing parameters could be used to track central effects of either HIV or ART.

N1-p2 recordings to gaps in broadband noise.

BACKGROUND: Normal temporal processing is important for the perception of speech in quiet and in difficult listening situations. Temporal resolution is commonly measured using a behavioral gap detection task, where the patient or subject must participate in the evaluation process. This is difficult to achieve with subjects who cannot reliably complete a behavioral test. However, recent research has investigated the use of evoked potential measures to evaluate gap detection. PURPOSE: The purpose of the current study was to record N1-P2 responses to gaps in broadband noise in normal hearing young adults. Comparisons were made of the N1 and P2 latencies, amplitudes, and morphology to different length gaps in noise in an effort to quantify the changing responses of the brain to these stimuli. It was the goal of this study to show that electrophysiological recordings can be used to evaluate temporal resolution and measure the influence of short and long gaps on the N1-P2 waveform. RESEARCH DESIGN: This study used a repeated-measures design. All subjects completed a behavioral gap detection procedure to establish their behavioral gap detection threshold (BGDT). N1-P2 waveforms were recorded to the gap in a broadband noise. Gap durations were 20 msec, 2 msec above their BGDT, and 2 msec. These durations were chosen to represent a suprathreshold gap, a near-threshold gap, and a subthreshold gap. STUDY SAMPLE: Fifteen normal-hearing young adult females were evaluated. Subjects were recruited from the local university community. DATA COLLECTION AND ANALYSIS: Latencies and amplitudes for N1 and P2 were compared across gap durations for all subjects using a repeated-measures analysis of variance. A qualitative description of responses was also included. RESULTS: Most subjects did not display an N1-P2 response to a 2 msec gap, but all subjects had present clear evoked potential responses to 20 msec and 2+ msec gaps. Decreasing gap duration toward threshold resulted in decreasing waveform amplitude. However, N1 and P2 latencies remained stable as gap duration changed. CONCLUSIONS: N1-P2 waveforms can be elicited by gaps in noise in young normal-hearing adults. The responses are present as low as 2 msec above behavioral gap detection thresholds (BGDT). Gaps that are below BGDT do not generally evoke an electrophysiological response. These findings indicate that when a waveform is present, the gap duration is likely above their BGDT. Waveform amplitude is also a good index of gap detection, since amplitude decreases with decreasing gap duration. Future studies in this area will focus on various age groups and individuals with auditory disorders.

Patient-reported auditory functions after stroke of the central auditory pathway.

BACKGROUND AND PURPOSE: Auditory functional limitations experienced by patients after stroke of the central auditory pathways remain underinvestigated. Purpose- To measure patient-reported hearing difficulties in everyday life in nonaphasic patients with stroke of the auditory brain versus normal control subjects. To examine how hearing difficulties correlate with auditory tests and site of lesion in individual cases. METHODS: We recruited 21 individuals with auditory brain stroke (excluding those with aphasia) diagnosed on the basis of a brain MRI conducted 1 to 2 weeks after the stroke and assessed in the chronic stage of stroke. Twenty-three controls matched for age and hearing were also recruited. All subjects completed the Amsterdam Inventory for Auditory Disability (consisting of subscales of sound detection, recognition, localization, speech in quiet, speech in noise) and underwent baseline audiometry and central auditory processing tests (dichotic digits, frequency and duration patterns, gaps in noise). RESULTS: Sound recognition and localization subscores of the inventory were significantly worse in case subjects versus control subjects, with severe and significant functional limitation (z score >3) reported by 9 out of 21 case subjects. None of the inventory subscales correlated with audiometric thresholds, but localization and recognition subscales showed a moderate to strong correlation with dichotic digits (left ear) and pattern tests. CONCLUSIONS: A substantial proportion of patients may experience and report severe auditory functional limitations not limited to speech sounds after stroke of the auditory brain. A hearing questionnaire may help identify patients who require more extensive assessment to inform rehabilitation plans.

The Onset-Offset N1-P2 Cortical Auditory Evoked Response in Individuals With High-Frequency Sensorineural Hearing Loss: Responses to High- and Low-Frequency Narrowband Noise.

PURPOSE: This study aimed to determine whether onset-offset N1-P2 auditory evoked responses differ in amplitude, latency, and offset-to-onset trough-to-peak N1-P2 amplitude ratios (OOAR) between normal hearing (NH) sensitivity and moderate high-frequency sensorineural hearing loss (HFSNHL) groups when stimuli target regions of peripheral hearing sensitivity where the groups are in the normal range (i.e., 500 Hz) versus where they differ regarding presence of hearing loss (i.e., 4000 Hz). METHOD: Onset-offset N1-P2 auditory evoked responses were measured from 10 participants with normal hearing sensitivity and seven participants with moderate HFSNHL using 500-Hz and 4000-Hz narrowband noise (NBN) stimuli. Stimuli were 2000 ms with 40-ms rise-fall times presented at 50 dB SL referenced to stimulus behavioral thresholds. Amplitudes and latencies were analyzed for N1 and P2 onset and offset components via repeated measures analysis of variance (ANOVA). OOARs were compared between groups using one-way ANOVA and across stimuli per group using paired samples t tests. RESULTS: Despite dB SPL stimulus presentation differences between groups, there were no significant differences in individual/absolute amplitude and latency waveform components between groups for either stimulus. Derived comparative calculations of OOAR for 4000-Hz NBN were significantly larger (p < .025; NH: .39; HFSNHL: .62) for the group with HFSNHL than the group with NH sensitivity; 500-Hz NBN OOAR did not reach significance. OOARs revealed no significant difference between stimuli for the group with normal hearing sensitivity, with .38 OOAR for both stimuli (p = .961). OOAR comparisons for the HFSNHL group across stimuli were significant (p = .012), with the 4000-Hz NBN OOAR being nearly double the size of the 500-Hz NBN OOAR. CONCLUSIONS: OOARs may provide insight to the balance of excitatory and inhibitory neural firing in the central auditory nervous system (CANS). Larger OOARs may be a biomarker of reduced CANS inhibition, perhaps indicative of a homeostatic central auditory gain mechanism.

Neuroaudiological Considerations for the Auditory Brainstem Response and Middle Latency Response Revisited: Back to the Future.

The auditory brainstem response (ABR) and middle latency response (MLR) are two sets of evoked potentials that have made major contributions to the field of diagnostic audiology. Many of these contributions were guided by clinical research audiologists. Though many of these auditory evoked potentials (AEPs) are still being used diagnostically by audiologists, there has been a steep decline in their popularity both clinically and in the research laboratory. This is indeed most unfortunate because these AEPs could and should be advancing our field and benefitting many patients. In this article, some critical research is overviewed that addresses some of the reasons why these AEPs (ABR and MLR) are not being utilized as frequently as they should be for neuroauditory assessments. Reflecting on our past when ABR and MLR were more commonly used can serve as a model for our future. Multiple applications and the diagnostic value of these AEPs are presented in an effort to convince audiologists that these electrophysiologic procedures should be revisited and reapplied in the clinic and research settings. It is argued that the dwindling use of ABR and MLR (and AEPs in general) in the field of audiology is not only remarkably premature but also lacks good scientific grounding. While on the other hand, if applied clinically, the value of these AEPs is both substantial and promising.

Evidence of Validity and Normative Values of a New Auditory Backward Masking Test.

There are still no valid, clinically feasible instruments to assess backward masking (BM), an auditory temporal processing (ATP) phenomenon. The aim of this study was to develop, standardize and present evidence of validity for a behavioral test for BM assessment. Young adults were submitted to a BM test (BMT), where they were asked to identify a 1000 Hz pure tone followed by a narrowband noise with interstimulus intervals of 0 to 400 ms and signal-to-noise ratio (SNR) between -20 and -30 dB. The correct response rate and target sound detection threshold were calculated, and the results compared with those of young adults with abnormal ATP tests and older adults. Diagnostic accuracy analyses were carried out. Young adults with normal ATP obtained an average correct response rate of 89 and 87% for SNR -20 and -30 dB, respectively, with average thresholds between 10 and 15 ms and no difference between the left and right ears. Results were more consistent at SNR -20 dB, and the best diagnostic accuracy was obtained for SNR -20 dB, with good specificity, but low sensitivity. Normative values were obtained for the BMT, which proved to be clinically feasible, with preliminary evidence of validity.

Perspectives on dichotic listening and the corpus callosum.

The present review summarizes historic and recent research which has investigated the role of the corpus callosum in dichotic processing within the context of audiology. Examination of performance by certain clinical groups, including split brain patients, multiple sclerosis cases, and other types of neurological lesions is included. Maturational, age related, and genetic factors are also discussed. Finally, some attention is given to recent trends in audiology research to develop improved diagnostic and rehabilitation tools for individuals with dichotic deficits potentially related to callosal dysfunction.

Diagnostic accuracy of established central auditory processing test batteries in patients with documented brain lesions.

PURPOSE: The sensitivity, specificity, and efficiency of commonly used behavioral central auditory processing tests and test batteries were determined for 20 individuals with known lesions of the central auditory nervous system (CANS) and related auditory symptoms. RESEARCH DESIGN: Twenty-nine individuals with no known neurological involvement served as the control group. Both groups were administered dichotic digits (DD), competing sentences (CS), frequency patterns (FP), and low-pass filtered speech (FS) tests. DATA ANALYSIS: Diagnostic indices for individual tests and test batteries comprised of two, three, or four tests were calculated both using a lax criterion in which failure on only one test in a battery led to a positive diagnosis and using a strict criterion in which failure on all tests in the battery was necessary to trigger a positive diagnosis. RESULTS: The test battery providing the best balance between sensitivity and specificity varied as a function of criterion. The two-test DD-FP battery using a strict criterion demonstrated the best balance. CONCLUSIONS: Limitations of particular tests, the advantages of larger test batteries to more broadly examine multiple auditory processes, the degree to which the present results can be generalized clinically to populations without known brain lesions, and other clinical considerations are discussed.

The Onset-Offset N1-P2 Auditory Evoked Response in Individuals With High-Frequency Sensorineural Hearing Loss: Responses to Broadband Noise.

Purpose Clinical use of electrophysiologic measures has been limited to use of brief stimuli to evoke responses. While brief stimuli elicit onset responses in individuals with normal hearing and normal central auditory nervous system (CANS) function, responses represent the integrity of a fraction of the mainly excitatory central auditory neurons. Longer stimuli could provide information regarding excitatory and inhibitory CANS function. Our goal was to measure the onset-offset N1-P2 auditory evoked response in subjects with normal hearing and subjects with moderate high-frequency sensorineural hearing loss (HFSNHL) to determine whether the response can be measured in individuals with moderate HFSNHL and, if so, whether waveform components differ between participant groups. Method Waveforms were obtained from 10 participants with normal hearing and seven participants with HFSNHL aged 40-67 years using 2,000-ms broadband noise stimuli with 40-ms rise-fall times presented at 50 dB SL referenced to stimulus threshold. Amplitudes and latencies were analyzed via repeated-measures analysis of variance (ANOVA). N1 and P2 onset latencies were compared to offset counterparts via repeated-measures ANOVA after subtracting 2,000 ms from the offset latencies to account for stimulus duration. Offset-to-onset trough-to-peak amplitude ratios between groups were compared using a one-way ANOVA. Results Responses were evoked from all participants. There were no differences between participant groups for the waveform components measured. Response × Participant Group interactions were not significant. Offset N1-P2 latencies were significantly shorter than onset counterparts after adjusting for stimulus duration (normal hearing: 43 ms shorter; HFSNHL: 47 ms shorter). Conclusions Onset-offset N1-P2 responses were resistant to moderate HFSNHL. It is likely that the onset was elicited by the presentation of a sound in silence and the offset by the change in stimulus envelope from plateau to fall, suggesting an excitatory onset response and an inhibitory-influenced offset response. Results indicated this protocol can be used to investigate CANS function in individuals with moderate HFSNHL. Supplemental Material https://doi.org/10.23641/asha.14669007.

Auditory Hallucinations: An Audiological Horizon?

BACKGROUND: Interesting data and theories have emerged regarding auditory hallucinations (AHs) in patients with schizophrenia. The possibility that these patients may have changes in the anatomy of the auditory cortex and/or subcortical structures of the central auditory nervous system and present with deficits on audiological tests is important information to the audiology community. However, it seems clear that, in general, audiologists are not sufficiently aware of these findings. PURPOSE: There are two main purposes of this article: (1) to educate audiologists about AHs related to schizophrenia and related issues, and (2) to encourage audiologists and hearing scientists to become involved in the evaluation and research of AHs. This fascinating disorder is one in which audiologists/hearing scientists are well suited to make a significant contribution. RESEARCH DESIGN: A review and synthesis of the literature was conducted. Relevant literature was identified through PubMed, Google Scholar, as well as independent book chapters and article searches. Keywords driving the searches were AHs, auditory illusions, verbal and musical hallucinations, schizophrenia, and central auditory disorders. Given the currency of the topic, the information collected was primarily between 1990 and 2020. STUDY SAMPLE: The review is organized around categorization, prevalence, models, mechanisms, anatomy, pathophysiology, and audiological correlates related to AHs. DATA COLLECTION AND ANALYSIS: Searches were conducted using well-known search engines and manual searches by each author. This information on AHs was then analyzed collectively by the authors for useful background and relevance, as well as important for the field of audiology. RESULTS: Several anatomical, physiological, and functional imaging studies have shown compromise of the auditory cortex in those with schizophrenia and AHs. Potentially related to this, are studies that demonstrated sub-par performance on behavioral audiologic measures for this unique clinical population. These findings align well with the kind of hearing disorder for which audiologists are well-trained to make significant contributions. CONCLUSION: Neurobiological and audiological evidence is accumulating on patients with schizophrenia and AH potentially rendering it as both an auditory and psychiatric disorder. Audiologists should consider expanding their horizon and playing a role in the clinical investigation of this disorder.

Morphological changes in the middle latency response using maximum length sequence stimuli.

BACKGROUND: The middle latency response (MLR) can be a powerful tool for assessing integrity of cortical and subcortical auditory structures. Most research on the MLR, however, is constrained to relatively slow repetition rates by the time window necessary for response acquisition. Maximum length sequence (MLS) paradigms enable the recording of the MLR at high repetition rates, which could reduce test time and provide information about the behavior of auditory structures at rapid rates of stimulation. PURPOSES: To examine potential timing advantages and differences in waveforms between an MLS-MLR paradigm compared to a conventional MLR paradigm (Experiment 1), and to examine effects of rate on MLR morphology within the MLS paradigm (Experiment 2). RESEARCH DESIGN: A repeated measures study. All subjects within each experiment underwent every condition for that experiment. STUDY SAMPLE: Ten young adult female subjects participated in each experiment of this study. All subjects had normal hearing and negative neurological history. DATA COLLECTION AND ANALYSIS: Latency and amplitude values as well as the presence/absence of Na, Pa, Nb, and Pb components of the MLR were measured. Comparisons were made between the MLS-MLR and conventional MLR paradigms, as well as between repetition rates within the MLS-MLR paradigm. RESULTS: Significant latency and amplitude differences were found between MLS and conventional MLR paradigms. The late components of the MLR (Nb, Pb) were present significantly more often when the MLS paradigm was used. No timing advantage was found with the MLS-MLR paradigm. Within the MLS paradigm, as repetition rate increases, latency becomes significantly shorter and amplitude significantly lower. CONCLUSIONS: Middle latency responses evoked by the MLS-MLR paradigm show significant differences from those evoked by a conventional MLR paradigm. The MLS-MLR paradigm can reliably evoke the late components (Nb, Pb) of the MLR and may be an important clinical tool for future investigation of these elements.

The effect of visual and audiovisual competition on the auditory N1-P2 evoked potential.

BACKGROUND: Use of a competition stimuli (e.g., video) in clinical settings is a widespread practice, yet the effects of these stimuli on evoked potentials are not well understood. PURPOSE: The present investigation acquired the click evoked auditory N1-P2 in quiet and in two types of competition: during presentation of an unrelated visual stimulus or audiovisual stimulus. Responses were acquired in each of these conditions at two click stimulus levels (i.e., 35 and 65 dBnHL) to determine if the effect of competition was greater closer to threshold. An attempt was made to quantify effect robustness by examining within- and between-session reliability. RESEARCH DESIGN: Repeated measures ANOVA. STUDY SAMPLE: 17 normal hearing female subjects. RESULTS: Findings indicated a significant effect of audiovisual competition on the amplitude of the N1-P2, and a borderline significant effect of visual competition on this index. The extent of visual competition was better conveyed when examined on a case-by-case basis, in which was revealed a subgroup of the sample that was negatively affected by visual competition. There was no interaction between competition and click stimulus level. CONCLUSIONS: Although competition stimuli can negatively affect the amplitude of the N1-P2, consideration should be given to subjects on a case-by-case basis to warrant if removal of this stimulus is necessary.

GIN (Gaps-In-Noise) performance in the pediatric population.

BACKGROUND: The recently developed Gaps-In-Noise (GIN) test has provided a new diagnostic tool for the detection of temporal resolution deficits. Previous reports indicate that the GIN is a relatively sensitive tool for the diagnosis of central auditory processing disorder ([C]APD) in adult populations. PURPOSE: The purpose of the present study was to determine the feasibility of the GIN test in the pediatric population. RESEARCH DESIGN: This was a prospective pseudorandomized investigation. STUDY SAMPLE: This investigation involved administration of the GIN to 72 participants divided into six groups of normal children ranging from 7 through 18 years of age. DATA COLLECTION AND ANALYSIS: The approximate GIN threshold (the shortest gap duration for which at least four of six gaps were correctly identified) served as the dependent variable. Results were analyzed using an ANOVA to examine between- and within-group differences. RESULTS: No statistically significant differences were seen in GIN thresholds among age groups. In addition, within group analysis yielded no statistically significant differences between ears within each age group. No developmental effect was seen in GIN thresholds between the ages of 7 and 18 years. Children as young as age 7 are able to complete the GIN with no significant difficulty and perform at levels commensurate with normal adults. The absence of ear differences suggests that temporal resolution as measured by the GIN is an auditory process that develops relatively early and symmetrically (i.e., no laterality or ear dominance effects). CONCLUSIONS: The GIN procedure appears to be a feasible measure of temporal resolution in both pediatric and adult populations.

Clinical Expertise Is Core to an Evidence-Based Approach to Auditory Processing Disorder: A Reply to Neijenhuis et al. 2019.

The opinion article "An Evidence-based Perspective on Misconceptions Regarding Pediatric Auditory Processing Disorder" by Neijenhuis et al. (1) presents a distorted view of the evidence-based approach used in medicine. The authors focus on the amorphous non-diagnostic entity "listening difficulties" not auditory processing disorder (APD) and create confusion that could jeopardize clinical services to individuals with APD. In our perspective article, we rebut Neijenhuis et al. (1), and more importantly, we present a rationale for evidence-based practice founded on the premise that research on APD is only clinically applicable when conducted on clinical populations diagnosed with APD.

An electrophysiological measure of binaural hearing in noise.

BACKGROUND: A common complaint of patients with (central) auditory processing disorder is difficulty understanding speech in noise. Because binaural hearing improves speech understanding in compromised listening situations, quantifying this ability in different levels of noise may yield a measure with high clinical utility. PURPOSE: To examine binaural enhancement (BE) and binaural interaction (BI) in different levels of noise for the auditory brainstem response (ABR) and middle latency response (MLR) in a normal hearing population. RESEARCH DESIGN: An experimental study in which subjects were exposed to a repeated measures design. STUDY SAMPLE: Fifteen normal hearing female adults served as subjects. Normal hearing was assessed by pure-tone audiometry and otoacoustic emissions. INTERVENTION: All subjects were exposed to 0, 20, and 35 dB effective masking (EM) of white noise during monotic and diotic click stimulation. DATA COLLECTION AND ANALYSIS: ABR and MLR responses were simultaneously acquired. Peak amplitudes and latencies were recorded and compared across conditions using a repeated measures analysis of variance (ANOVA). RESULTS: For BE, ABR results showed enhancement at 0 and 20 dB EM, but not at 35 dB EM. The MLR showed BE at all noise levels, but the degree of BE decreased with increasing noise level. For BI, both the ABR and MLR showed BI at all noise levels. However, the degree of BI again decreased with increasing noise level for the MLR. CONCLUSIONS: The results demonstrate the ability to measure BE simultaneously in the ABR and MLR in up to 20 dB of EM noise and BI in up to 35 dB EM of noise. Results also suggest that ABR neural generators may respond to noise differently than MLR generators.