Effects of Adding Monaural and Binaural Noise to a Dichotic Listening Task.

BACKGROUND: The Dichotic Digits Test (DDT) evaluates central auditory nervous system (CANS) dysfunction. The DDT is widely used in audiology clinics worldwide because it is clinically efficient and has good sensitivity and specificity for CANS lesions. However, the DDT shows a strong ceiling effect, which can mitigate its ability to detect subtle CANS dysfunction. PURPOSE: This study examines the effects of adding monaural and binaural speech-spectrum noise to the DDT in an effort to make the test more taxing to the CANS and thereby reduce the observed ceiling effect. RESEARCH DESIGN: This was an experimental repeated measures study. STUDY SAMPLE: The participants were 20 adults aged 18-50 years with normal, bilaterally symmetric peripheral hearing sensitivity. DATA COLLECTION AND ANALYSIS: Each participant was administered one standard DDT test list (no noise added) and DDT test lists with binaural, monaural right, and monaural left noise added. For each of the noise-added conditions, lists were administered at two different signal-to-noise ratios (SNRs), for a grand total of seven DDT test lists per participant, presented in randomized order. Monaural and binaural noise effects on DDT scoring indices (Right and Left Ear Percent Correct Scores, Combined Total Percent Correct Scores, and Dichotic Difference Scores), as well as noise effects on the Right Ear Advantage (REA) for speech, were examined. Mixed model analyses of variance (ANOVAs) were used to examine fixed effects and interactions of Noise Condition and Ear. RESULTS: Adding noise to the standard DDT systematically reduced Right and Left Ear Percent Correct Scores and Combined Total Percent Correct Scores. Statistically significant differences on all indices were found between monaural and binaural noise-added conditions, suggesting a possible advantage for binaural listening in noise. CONCLUSIONS: These findings suggest that adding noise to tests of dichotic listening increases the difficulty of the task, and that further investigation of dichotic listening patterns in noise could potentially lead to more sensitive clinical evaluations of CANS integrity and function.

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.

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.

Knowledge gaps for functional outcomes after multilobar resective and disconnective pediatric epilepsy surgery: Conference Proceedings of the Patient-Centered Stakeholder Meeting 2019.

For children with medication-resistant epilepsy who undergo multilobar or hemispheric surgery, the goal of achieving seizure freedom is met with a variety of potential functional consequences, both favorable and unfavorable. However, there is a paucity of literature that comprehensively addresses the cognitive, medical, behavioral, orthopedic, and sensory outcomes across the lifespan following large epilepsy surgeries in childhood, leaving all stakeholders underinformed with regard to counseling and expectations. Through collaboration between clinicians, researchers, and patient/caregiver stakeholders, the "Functional Impacts of Large Resective or Disconnective Pediatric Epilepsy Surgery: Identifying Gaps and Setting PCOR Priorities" meeting was convened on July 18, 2019, to identify gaps in knowledge and inform various patient-centered research initiatives. Clinicians and researchers with content expertise presented the best available data in each functional domain which is summarized here. As a result of the meeting, the top three consensus priorities included research focused on postoperative: (1) hydrocephalus; (2) mental health issues; and (3) literacy and other educational outcomes. The proceedings of this meeting mark the first time research on functional outcomes after resective and disconnective pediatric epilepsy surgery has been codified and shared among multidisciplinary stakeholders. This joint initiative promotes continued collaboration in the field and ensures that advancements align with actual patient and family needs and experiences. Collaboration around common objectives will lead to better informed counseling around postoperative expectations and management for children undergoing epilepsy surgery.

Investigating the Role of Auditory Processing Abilities in Long-Term Self-Reported Hearing Aid Outcomes among Adults Age 60+ Years.

BACKGROUND: Self-reported hearing aid outcomes among older adults are variable and important to improve. The extent of the role of auditory processing in long-term hearing aid outcomes is not well understood. PURPOSE: To determine how auditory processing abilities are related to self-reported hearing aid satisfaction and benefit along with either aided audibility alone or exploratory factors suggested by previous literature. RESEARCH DESIGN: Descriptive analyses and multiple regression analyses of cross-sectional self-reported outcomes. STUDY SAMPLE: Adult participants, >60 years (n = 78), fitted with bilateral hearing aids to treat symmetric, mild to moderate sensorineural hearing loss. DATA COLLECTION AND ANALYSIS: Participants were recruited from a single audiology clinic to complete a series of questionnaires, behavioral assessments, and obtain data from their hearing aids, including real ear measures and data logging of hearing aid use. Multiple linear regressions were used to determine the amount of variance explained by predictive factors in self-reported hearing aid satisfaction and benefit. The primary predictive factors included gap detection threshold, spatial advantage score, dichotic difference score, and aided audibility. Exploratory factors included personality, self-efficacy, self-report of disability, and hearing aid use. All interpretations of statistical significance used p < 0.05. Effect sizes were determined using Cohen's f 2 with a medium effect suggesting clinical relevance. RESULTS: Gap detection threshold was a statistically significant predictor in both primary regression models with a medium effect size for satisfaction and a small effect size for benefit. When additional exploratory factors were included in the regression models with auditory processing abilities, gap detection and self-efficacy were both significant predictors of hearing aid satisfaction with medium effect sizes, explaining 10 and 17% of the variance, respectively. There were no medium effect sizes found for other predictor variables in either the primary or exploratory hearing aid benefit models. Additional factors were statistically significant in the models, explaining a small amount of variance, but did not meet the medium effect size criterion. CONCLUSION: This study provides initial evidence supporting the incorporation of measures of gap detection ability and hearing aid self-efficacy into clinical practice for the interpretation of postfitting long-term hearing aid satisfaction.

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.

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.

Predicting Hearing Aid Satisfaction in Adults: A Systematic Review of Speech-in-noise Tests and Other Behavioral Measures.

OBJECTIVES: Adults with hearing loss report a wide range of hearing aid satisfaction that does not significantly correlate to degree of hearing loss. It is not clear which auditory behavioral factors do contribute to hearing aid satisfaction. While poor speech understanding in noise is known to contribute to dissatisfaction, there are many categories of this type of assessment. The purpose of this systematic review is to answer the question, "Are behavioral pre-fitting measures using speech and nonspeech materials related to hearing aid satisfaction among adults?" DESIGN: Six electronic databases were searched to find peer-reviewed studies published before June 2020. The included studies reported on the relationship between auditory behavioral measures and hearing aid satisfaction alone or globally with other outcome domains among adults with hearing loss. Six types of behavioral prefitting measures were evaluated: speech recognition in quiet (% correct), speech recognition in noise (% correct), reception thresholds for speech-in-noise, speech-based subjective ratings, dichotic speech tests, and tests using nonspeech material. Each relevant study was independently reviewed by two reviewers. Methodological quality was evaluated in each included study using the American Speech-Language-Hearing Association's level of evidence ratings. RESULTS: There were 1342 articles identified in the systematic review process. After duplicates were removed and specific inclusion criteria were applied, 21 studies were included. All studies included had a 0 to 4 methodological quality rating indicating weak to moderate internal validity. The tests that showed potential for clinical application due to significant correlations with satisfaction were the QuickSIN, the synthetic sentence identification, the hearing in noise test, and the acceptable noise level test. Audibility, as measured by degree of hearing loss, was not significantly correlated to hearing aid satisfaction in the 13 studies that reported on this measure. CONCLUSIONS: Based on this review, results indicated that speech-in-noise tests had the highest associations to hearing aid satisfaction, suggesting a greater role for assessment of speech-in-noise perception in auditory rehabilitation. This is an important finding for clinical practice, given that audibility was not a significant factor in predicting satisfaction. Overall, the results from this review show a need for well-designed, high-quality, prospective studies assessing the predictive value of prefitting measures on hearing aid satisfaction with current hearing aid models.

Behavioral and Hemodynamic Changes Following Dichotic Training in Patients with Neurological Deficits of the Auditory Nervous System: A Case Series.

BACKGROUND: Dichotic listening occurs when one attends to different acoustical messages presented simultaneously to both ears. This is important for understanding speech in compromised listening situations, such as background noise. Deficits in dichotic listening can be remediated by participating in auditory training. We present two patients with binaural integration deficits who underwent dichotic interaural intensity difference (DIID) training. PURPOSE: The purpose of this investigation is to demonstrate improvement of dichotic listening deficits following DIID training in neurological patients seen clinically for hearing issues. RESEARCH DESIGN: This was a case series utilizing a pre- and posttreatment design. STUDY SAMPLE: This case series utilized two female participants who demonstrated binaural integration deficits during an auditory processing evaluation. INTERVENTION: The participants underwent a pretraining auditory processing evaluation and functional magnetic resonance imaging (fMRI). Participants then underwent 12, 30-minute DIID training sessions followed by posttreatment auditory processing evaluations and fMRI. DATA COLLECTION AND ANALYSIS: Data was collected at the pretreatment appointment and then immediately following the completion of the training. RESULTS: Each patient demonstrated varying degrees of improvement on the posttreatment assessment. Case 1 showed significant improvement on the Speech-in-Noise-Revised (SPIN-R) test. fMRI showed changes in activation patterns following training. Case 2 demonstrated improved scores on the Dichotic Digits Test and SPIN-R and increased activation of the calcarine sulcus following training. CONCLUSION: Dichotic training can be an efficacious treatment for binaural integration deficits and may show evidence of improving speech understanding in noise. This case series demonstrates a promising therapy to help patients improve auditory function by improving dichotic listening skills.

GIN Test: A Meta-Analysis on Its Neurodiagnostic Value.

PURPOSE: A meta-analysis was conducted to evaluate how effective the Gaps-in-Noise (GIN) test is in separating populations who are and who are not at risk of having neurological damage related to the central auditory nervous system (CANS). This was investigated by asking three specific questions: (1) Does ear and side of lesion have an effect over the individual's performance? (2) How large is the difference in performance between control and neurological groups? (3) What are the diagnostic indices related to the GIN test? DATA COLLECTION AND ANALYSIS: A literature review was performed between April 2016 and April 2017. The eligibility criteria for inclusion were as follows: (1) studies that used the GIN test as an outcome measure, (2) studies that included adult participants who either had confirmed lesions or were at risk of having lesions to the CANS or related regions, and (3) studies that had a neurologically normal control group. From relevant studies that met eligibility criteria, information regarding study design, participants, lesion details and origins, use of additional assessments, GIN performance scores for both control (CTRL) and neurological (NRLG) groups, GIN cutoff scores and proportion of individuals with normal and abnormal performances were all included. RESULTS: Nine studies were included, totaling 221 participants in NRLG (stroke = 90, epilepsy = 67, and blast exposure [BLST] = 64) and 262 in CTRL (Stroke = 106, Epilepsy = 98, and BLST = 58). No significant ear effects related to side of lesion were observed for the GIN test in neurological patients nor were there significant ear differences for normal individuals with symmetrically normal hearing. The GIN demonstrated consistency among different neurological populations, presented good sensitivity and specificity rates, and was overall accurate in discriminating between participants with neuroauditory lesions from neurologically normal individuals. CONCLUSIONS: The GIN is thus a clinically effective measure that provides insight into the CANS integrity and may aid in clinical diagnosis by distinguishing between populations who are and who are not at risk of having neurological damage affecting the CANS.

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.

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.

Enhancement of the Auditory Late Response (N1-P2) by Presentation of Stimuli From an Unexpected Location.

BACKGROUND: Passive electrophysiological protocols, such as the middle latency response and speech auditory brainstem response, are often advocated in the objective assessment of central auditory processing disorder (CAPD). However, few established electrophysiological protocols exist for CAPD assessment that have patients participate in active tasks which more closely approximate real-world listening. To this end, the present study used a discrimination task (i.e., oddball paradigm) to measure an enhancement of the auditory late response (N1-P2) that occurs when participants direct their auditory attention toward speech arising from an unexpected spatial location. PURPOSE: To establish whether N1-P2 is enhanced when auditory attention is directed toward an unexpected location during a two-word discrimination task. In addition, it was also investigated whether any enhancements in this response were contingent on the stimulus being counted as part of the oddball paradigm. RESEARCH DESIGN: Prospective study with a repeated measures design. STUDY SAMPLE: Ten normal hearing adults, with an age range of 18-24 years. DATA COLLECTION AND ANALYSIS: The N1 and P2 latencies and peak-to-peak amplitudes were recorded during a P300 paradigm. A series of repeated measures of analysis of variance and a correlation analysis was performed. RESULTS: There was a significant effect of stimulus location, in which words arising from the unexpected location showed a larger N1-P2 peak-to-peak amplitude and an earlier N1 latency. This effect was seen regardless of whether or not participants had to count the word total in memory. CONCLUSIONS: These findings suggest that spatial enhancement of the N1-P2 is a fairly robust phenomenon in normal hearing adult listeners. Additional studies are needed to determine whether this enhancement is absent or reduced in patients with CAPD.

The Middle Latency Response: A Review of Findings in Various Central Nervous System Lesions.

BACKGROUND: The middle latency response (MLR) first came to light as an auditory evoked potential in 1958. Since then, it has aroused substantial interest and investigation by clinicians and researchers alike. In recent history, its use and popularity have dwindled in tandem with various other auditory evoked potentials in audiology. One area for which MLR research and application has been overlooked is its potential value in measuring the neural integrity of the auditory thalamocortical pathway. In a broader sense, the MLR, when combined with the auditory brain stem response, can provide information concerning the status of much of the central auditory system pathways. This review is intended to provide information concerning the MLR as a measure of central auditory function for the reader to consider. PURPOSE: To review and synthesize the scientific literature regarding the potential value of the MLR in assessing the integrity of the central auditory system and to provide the reader an informed perspective on the value of the MLR in this regard. Information is also provided on the MLR generator sites and fundamental characteristics of this evoked potential essential to its clinical and or research application. RESEARCH DESIGN: A systematic review and synthesis of the literature focusing on the MLR and lesions of the central auditory system. STUDY SAMPLE: Studies and individual cases were reviewed and analyzed that evidenced documented lesions of the central auditory nervous system. DATA COLLECTION AND ANALYSIS: The authors searched and reviewed the literature (journal articles, book chapters, and books) pertaining to central auditory system lesion effects on the MLR. RESULTS: Although findings varied from study to study, overall, the MLR was reasonably sensitive and specific to neurological compromise of the central auditory system. This finding is consistent with the generator sites of this evoked potential. CONCLUSIONS: The MLR is a valuable tool for assessing the integrity of the central auditory system. It should be of interest to the clinician or researcher who focuses their attention on the function and dysfunction of the higher auditory system.

The Relationship between Central Auditory Processing, Language, and Cognition in Children Being Evaluated for Central Auditory Processing Disorder.

BACKGROUND: Pediatric central auditory processing disorder (CAPD) is frequently comorbid with other childhood disorders. However, few studies have examined the relationship between commonly used CAPD, language, and cognition tests within the same sample. PURPOSE: The present study examined the relationship between diagnostic CAPD tests and "gold standard" measures of language and cognitive ability, the Clinical Evaluation of Language Fundamentals (CELF) and the Wechsler Intelligence Scale for Children (WISC). RESEARCH DESIGN: A retrospective study. STUDY SAMPLE: Twenty-seven patients referred for CAPD testing who scored average or better on the CELF and low average or better on the WISC were initially included. Seven children who scored below the CELF and/or WISC inclusion criteria were then added to the dataset for a second analysis, yielding a sample size of 34. DATA COLLECTION AND ANALYSIS: Participants were administered a CAPD battery that included at least the following three CAPD tests: Frequency Patterns (FP), Dichotic Digits (DD), and Competing Sentences (CS). In addition, they were administered the CELF and WISC. Relationships between scores on CAPD, language (CELF), and cognition (WISC) tests were examined using correlation analysis. RESULTS: DD and FP showed significant correlations with Full Scale Intelligence Quotient, and the DD left ear and the DD interaural difference measures both showed significant correlations with working memory. However, ∼80% or more of the variance in these CAPD tests was unexplained by language and cognition measures. Language and cognition measures were more strongly correlated with each other than were the CAPD tests with any CELF or WISC scale. Additional correlations with the CAPD tests were revealed when patients who scored in the mild-moderate deficit range on the CELF and/or in the borderline low intellectual functioning range on the WISC were included in the analysis. CONCLUSIONS: While both the DD and FP tests showed significant correlations with one or more cognition measures, the majority of the variance in these CAPD measures went unexplained by cognition. Unlike DD and FP, the CS test was not correlated with cognition. Additionally, language measures were not significantly correlated with any of the CAPD tests. Our findings emphasize that the outcomes and interpretation of results vary as a function of the subject inclusion criteria that are applied for the CELF and WISC. Including participants with poorer cognition and/or language scores increased the number of significant correlations observed. For this reason, it is important that studies investigating the relationship between CAPD and other domains or disorders report the specific inclusion criteria used for all tests.

Perspectives on the Pure-Tone Audiogram.

BACKGROUND: The pure-tone audiogram, though fundamental to audiology, presents limitations, especially in the case of central auditory involvement. Advances in auditory neuroscience underscore the considerably larger role of the central auditory nervous system (CANS) in hearing and related disorders. Given the availability of behavioral audiological tests and electrophysiological procedures that can provide better insights as to the function of the various components of the auditory system, this perspective piece reviews the limitations of the pure-tone audiogram and notes some of the advantages of other tests and procedures used in tandem with the pure-tone threshold measurement. PURPOSE: To review and synthesize the literature regarding the utility and limitations of the pure-tone audiogram in determining dysfunction of peripheral sensory and neural systems, as well as the CANS, and to identify other tests and procedures that can supplement pure-tone thresholds and provide enhanced diagnostic insight, especially regarding problems of the central auditory system. RESEARCH DESIGN: A systematic review and synthesis of the literature. DATA COLLECTION AND ANALYSIS: The authors independently searched and reviewed literature (journal articles, book chapters) pertaining to the limitations of the pure-tone audiogram. RESULTS: The pure-tone audiogram provides information as to hearing sensitivity across a selected frequency range. Normal or near-normal pure-tone thresholds sometimes are observed despite cochlear damage. There are a surprising number of patients with acoustic neuromas who have essentially normal pure-tone thresholds. In cases of central deafness, depressed pure-tone thresholds may not accurately reflect the status of the peripheral auditory system. Listening difficulties are seen in the presence of normal pure-tone thresholds. Suprathreshold procedures and a variety of other tests can provide information regarding other and often more central functions of the auditory system. CONCLUSIONS: The audiogram is a primary tool for determining type, degree, and configuration of hearing loss; however, it provides the clinician with information regarding only hearing sensitivity, and no information about central auditory processing or the auditory processing of real-world signals (i.e., speech, music). The pure-tone audiogram offers limited insight into functional hearing and should be viewed only as a test of hearing sensitivity. Given the limitations of the pure-tone audiogram, a brief overview is provided of available behavioral tests and electrophysiological procedures that are sensitive to the function and integrity of the central auditory system, which provide better diagnostic and rehabilitative information to the clinician and patient.