Lack of a coherent theory limits the diagnostic and prognostic value of the (central) auditory processing disorder: a theoretical and clinical perspective

PURPOSE OF REVIEW

To consider pertinent issues towards developing a coherent theory of the auditory processing disorder (APD). By identifying the conceptual and methodological shortcomings that have thwarted development in this area for decades, we propose solutions to achieve a veridical endpoint to advance the field.

RECENT FINDINGS

Concerted efforts in the theoretical, experimental, and clinical domains have focused on validating the APD by demonstrating the " modality specificity " of the deficit. The importance of this conceptual framework is the delineation of auditory-perceptual dysfunctions from more generalized " supra modal" deficits, like those related to attention, memory, and language. Because contemporary schemata have limited the assessment of APD to auditory tasks alone ( unimodal testing), functional dissociations cannot be established, indeterminate diagnoses are problematic, and progress remains unduly constrained. The use of matched tasks in multiple sensory modalities is advocated as a diagnostic imperative to remedy this deficiency.

SUMMARY

Themes covered by this review include the need to develop a coherent theory of APD, to identify and limit factors which confound a valid diagnosis, and to validate the diagnosis by demonstrating the " modality specificity " of the deficit. Without an obligatory theoretical designation, the APD will remain as an obscure and controversial entity, limited to indeterminate test results and misdiagnoses.

Evolving the concept of APD

OBJECTIVE

To consider the evolving concept of auditory processing disorder (APD).

DESIGN

Narrative review and opinion piece.

STUDY SAMPLE

Eight approaches to APD described in the literature and its definitions by ten societies or groups from around the world.

RESULTS

The dominant conceptualisation of APD remains one of disorders (or at least deficits) in the bottom-up processing of sound in the primary auditory nervous system that are not due to higher order (top-down) language or cognitive deficits. Challenges to this conceptualisation question the relevance of (bottom-up) AP to listening, learning and language. These challenges are rejected by some groups who maintain the dominant bottom-up conceptualisation of APD, but accepted by others who suggest APD be reconceptualised to include top-down processing of sound or attempts to define APD be de-emphasised in favour of a hierarchical approach to listening difficulties.

CONCLUSIONS

To reconcile these challenges, the concept of APD could be better evolved by considering it as a spectrum disorder spanning from bottom-up AP to the top-down cognitive processes (particularly attention) that affect it.

Age-Related Declines in Early Sensory Memory: Identification of Rapid Auditory and Visual Stimulus Sequences

Age-related temporal-processing declines of rapidly presented sequences may involve contributions of sensory memory. This study investigated recall for rapidly presented auditory (vowel) and visual (letter) sequences presented at six different stimulus onset asynchronies (SOA) that spanned threshold SOAs for sequence identification. Younger, middle-aged, and older adults participated in all tasks. Results were investigated at both equivalent performance levels (i.e., SOA threshold) and at identical physical stimulus values (i.e., SOAs). For four-item sequences, results demonstrated best performance for the first and last items in the auditory sequences, but only the first item for visual sequences. For two-item sequences, adults identified the second vowel or letter significantly better than the first. Overall, when temporal-order performance was equated for each individual by testing at SOA thresholds, recall accuracy for each position across the age groups was highly similar. These results suggest that modality-specific processing declines of older adults primarily determine temporal-order performance for rapid sequences. However, there is some evidence for a second amodal processing decline in older adults related to early sensory memory for final items in a sequence. This selective deficit was observed particularly for longer sequence lengths and was not accounted for by temporal masking.

Characteristics of Auditory Processing Disorders: A Systematic Review

PURPOSE

The purpose of this review article is to describe characteristics of auditory processing disorders (APD) by evaluating the literature in which children with suspected or diagnosed APD were compared with typically developing children and to determine whether APD must be regarded as a deficit specific to the auditory modality or as a multimodal deficit.

METHOD

Six electronic databases were searched for peer-reviewed studies investigating children with (suspected) APD in comparison with typically developing peers. Relevant studies were independently reviewed and appraised by 2 reviewers. Methodological quality was quantified using the American Speech-Language-Hearing Association's levels of evidence.

RESULTS

Fifty-three relevant studies were identified. Five studies were excluded because of weak internal validity. In total, 48 studies were included, of which only 1 was classified as having strong methodological quality. Significant dissimilarities were found between children referred with listening difficulties and controls. These differences relate to auditory and visual functioning, cognition, language, reading, and physiological and neuroimaging measures.

CONCLUSIONS

Methodological quality of most of the incorporated studies was rated moderate due to the heterogeneous groups of participants, inadequate descriptions of participants, and the omission of valid and reliable measurements. The listening difficulties of children with APD may be a consequence of cognitive, language, and attention issues rather than bottom-up auditory processing.

Simulating the effects of common and specific abilities on test performance: an evaluation of factor analysis

PURPOSE

Factor analysis is a useful technique to aid in organizing multivariate data characterizing speech, language, and auditory abilities. However, knowledge of the limitations of factor analysis is essential for proper interpretation of results. The present study used simulated test scores to illustrate some characteristics of factor analysis.

METHOD

Linear models were used to simulate test scores that were determined by multiple latent variables. These simulated test scores were evaluated with principal components analysis and, in certain cases, structural equation modeling. In addition, a subset of simulated individuals characterized by poor test performance was examined.

RESULTS

The number of factors recovered and their identity do not necessarily correspond to the structure of the latent variables that generated the test scores. The first principal component may represent variance from multiple uncorrelated sources. Practices such as correction or control for general cognitive ability may produce misleading results.

CONCLUSIONS

Inferences from the results of factor analysis should be primarily about the structure of test batteries rather than the structure of human mental abilities. Researchers and clinicians should consider multiple sources of evidence to evaluate hypotheses about the processes generating test results.

Modeling individual subtests of the WAIS IV with multiple latent factors

Performance on a cognitive test can be viewed either as measuring a unitary function or as reflecting the operation of multiple factors. Individual subtests in batteries designed to measure human abilities are commonly modeled as a single latent factor. Several latent factors are then used to model groups of subtests. However these latent factors are not independent as they are related through hierarchical or oblique structures. As a result, the simple structure of subtest performance results in complex latent factors. The present study used structural equation modeling to evaluate several multidimensional models of the Wechsler Adult Intelligence Scales-fourth edition (WAIS-IV) subtests. Multidimensional models of subtest performance provided better model fit as compared to several previously proposed one dimensional models. These multidimensional models also generalized well to new samples of populations differing in age from that used to estimate the model parameters. Overall these results show that models that describe subtests as multidimensional functions of uncorrelated factors provided a better fit to the WAIS-IV correlations than models that describe subtests as one dimensional functions of correlated factors. There appears to be a trade-off in modeling subtests as one dimensional and modeling with homogeneous latent traits. More consideration should be given to models that include multiple uncorrelated latent factors as determinants of the performance on a given subtest. These results support the view that performance on any given cognitive test is potentially the result of multiple factors. Simple structure may be too simple.

A computer-based auditory sequential pattern test for school-aged children

OBJECTIVE

One type of test commonly used to assess auditory processing disorders (APD) is the Frequency Pattern Test, in which triads of pure tones of two different frequencies are presented, and participants are required to accurately report the sequence of tones, typically using a verbal response. The test is widely used clinically, but in its current format, is an under-exploited means of addressing some candidate processes, such as temporal ordering and frequency discrimination, which might be affected in APD. Here we describe a computer-based version of an auditory pattern perception test, the BirdSong Game, which was designed to be an engaging research tool for use with school-aged children.

METHODS

In this study, 128 children aged 6-10 with normal peripheral hearing were tested. The BirdSong Game application was used to administer auditory sequential pattern tests, via a touch-screen presentation and response interface. A conditioning step was included prior to testing, in order to ensure that participants were able to adequately discriminate between the test tones, and reliably describe the difference using their own vocabulary. Responses were collected either verbally or manually, by having participants press cartoon images on the touch-screen in the appropriate sequence. The data was examined for age, gender and response mode differences.

RESULTS

Findings on the auditory tests indicated a significant maturational effect across the age range studied, with no difference between response modes or gender.

CONCLUSIONS

The BirdSong Game is sensitive to maturational changes in auditory sequencing ability, and the computer-based design of the test has several advantages which make it a potentially useful clinical and research tool.

Using different criteria to diagnose (central) auditory processing disorder: how big a difference does it make?

PURPOSE

To quantify how 9 different diagnostic criteria affected potential (central) auditory processing disorder ([C]APD) diagnoses in a large sample of children referred for (central) auditory processing ([C]AP) assessment.

METHOD

A file review was conducted on 150 children (94 boys and 56 girls; ages 7.0-15.6 years) with normal peripheral hearing who had completed a (C)AP assessment involving low-pass filtered speech, competing sentences, 2-pair dichotic digits, and frequency patterns with linguistic and nonlinguistic report. Each child was classified as having or not having (C)APD based on 9 different sets of diagnostic criteria drawn from published technical reports, position statements, and selected research.

RESULTS

The rates of potential (C)APD diagnosis ranged from 7.3% for the strictest criteria to 96.0% for the most lenient criteria.

CONCLUSIONS

Until greater consensus is reached, any diagnosis of (C)APD should be qualified by an explicit statement of the criteria used. Calls to abandon the use of (C)APD as a global label should also be supported.

The relationship between brainstem temporal processing and performance on tests of central auditory function in children with reading disorders

PURPOSE

Studies using speech stimuli to elicit electrophysiologic responses have found approximately 30% of children with language-based learning problems demonstrate abnormal brainstem timing. Research is needed regarding how these responses relate to performance on behavioral tests of central auditory function. The purpose of the study was to investigate performance of children with dyslexia with and without abnormal brainstem timing and children with no history of learning or related disorders on behavioral tests of central auditory function.

METHOD

Performance of 30 school-age children on behavioral central auditory tests in common clinical use was examined: Group 1 (n = 10): dyslexia, abnormal brainstem timing; Group 2 (n = 10): dyslexia, normal brainstem timing; Group 3 (n = 10): typical controls.

RESULTS

Results indicated that all participants in Group 2 met diagnostic criteria for (central) auditory processing disorder [(C)APD], whereas only 4 participants in Group 1 met criteria. The Biological Marker of Auditory Processing (BioMARK) identified 6 children in Group 1 who did not meet diagnostic criteria for (C)APD but displayed abnormal brainstem timing.

CONCLUSIONS

Results underscore the importance of central auditory assessment for children with dyslexia. Furthermore, the BioMARK may be useful in identifying children with central auditory dysfunction who would not have been identified using behavioral methods of (C)APD assessment.

[Sequential information processing in children with and without auditory processing disorder]

BACKGROUND

It is a controversial issue whether sequential processing in children with auditory processing disorders (APD) is a unimodal auditory impairment.

PATIENTS AND METHODS

Normal achieving controls (n=12; mean age: 101.1 months; SD 20.3) and children referred to clinical facilities for assessment including children with monosymptomatic APD (n=25; mean age: 90.8 months; SD 9.8), children with developmental language disorder (DLD]) + APD (n=11; mean age: 89.5 months; SD 14.9), children with dyslexia + APD (n=10; mean age: 113.8 months; SD 17.1) were compared using the subtest digit recall of the German version of the K-ABC (Melchers & Preuss 2001) and the K-ABC subtest hand movements in the visual modality.

RESULTS

On average all groups tended to perform alike in visual sequential processing and memory (T-score>50). Normal controls (non-APD) showed on average the best test performance (T-score 57.4; SD 10.5), but the mean performance did not differ significantly from children with APD. All groups also presented on average normal test performance in the auditory modality however, children of the clinical groups were below the age mean (DLD + APD: T-W 43.1; SD 6.8; monosymptomatic APD: T-W 45.8; SD 9.8; dyslexia + APD: 46.7; SD5.8). Children with DLD + APD and those with monosymptomatic APD exhibited a significantly lower but not poor performance in auditory processing of sequences compared to their performance in visual sequential processing. The results of auditory and visual processing of sequences were significantly correlated in the clinical groups DLD + APD (0.58) and monosymptomatic APD (0.34), but not in the smallest group dyslexia + APD (0.48) and in normal achieving controls (0.32).

CONCLUSION

On the basis of the results of the present study it may be concluded that a normal test performance on visual measure does not exclude a bimodal or pansensory seriation disorder in children with APD. It does, however, indicate the existence of a primary auditory sequential processing deficit, because at least the processing of phonological and visual stimuli was not separately carried out in children with DLD + APD.

Measuring cognitive factors in speech comprehension: the value of using the Text Reception Threshold test as a visual equivalent of the SRT test

The ability to comprehend speech in noise is influenced by bottom-up auditory and top-down cognitive capacities. Separate examination of these capacities is relevant for various purposes. Speech-Reception-Threshold (SRT) tests measure an individual's ability to comprehend speech. This paper addresses the value of the Text-Reception-Threshold (TRT) test (a visual parallel of the SRT test) to assess the cognitive capacities allocated during speech comprehension. We conducted a secondary data analysis, including 87 normally-hearing adults (aged 18 to 78 years). Correlation coefficients between age, TRT, working memory (Spatial Span) and SRT were examined. The TRT and SRT correlated significantly (r = 0.30), supporting the value of TRT in explaining inter-individual differences in SRTs. The relations between age and TRT and between SSP and TRT were non-significant. The results indicate that the current TRT test does not fully cover the cognitive aspects relevant in speech comprehension. Adaptation of the test is required before clinical implementation can be considered.

[Assessment of central auditory processes in Spanish in children with dyslexia and controls. Binaural Fusion Test and Filtered Word Test]

OBJECTIVES

The aim is to assess the ability to discriminate words, using two psychoacoustic verbal tests of central auditory processes in Spanish: Binaural Fusion Test (BFT in its Spanish version) and Filtered Word Test (FWT in its Spanish version) in children with dyslexia and controls.

METHODS

One group of 40 dyslexic children was receiving therapy for dyslexia at the time of the tests. 40 children without dyslexia were selected as controls, out of 298 children who attended a public school.

RESULTS

The rate of males to females was 2/1 in the dyslexic group. The average correct answers for the BFT were 65-66% in dyslexic group and 75-80% in the control group. For the FWT they were 50-54% in the dyslexic group and 67-71% in the control group (student t <0.05).

CONCLUSIONS

These results contribute to make evident disorders in central auditory processing in children with dyslexia. We suggest using the tests with each patient in order to elaborate a rehabilitation plan.

Auditory processing disorders in adults and children: Evaluation of a test battery: Desórdenes del procesamiento auditivo en adultos y niños; evaluación de una batería de pruebas

A Dutch test battery comprising six different tests for auditory processing disorders was evaluated in a group of 49 adults and children (age 8-57 years) with auditory complaints despite normal audiometric thresholds. Percentile scores were derived from normal control groups (n = 132) to determine whether a subject passed or failed a test. A composite score was computed to reflect a general score on all the auditory processing tests. In order to gain insight into underlying auditory processes, factor analysis was performed. Normal scores on all the tests were seen in five subjects. The remaining 44 subjects had at least one test score that was below the cut-off point (10th percentile). Factor analysis provided evidence for a model comprising four auditory components: auditory sequencing, word recognition in noise, auditory closure, and auditory patterning. This model could be useful in the interpretation of scoring patterns. Although there were some differences in scoring patterns between the children and adults, the test battery proved to be useful in both groups.

Applicability of Central Auditory Processing Disorder Models

Purpose

Central auditory processing disorder ([C]APD) is a relatively recent construct that has given rise to 2 theoretical models: the Buffalo Model and the Bellis/Ferre Model. These models describe 4 and 5 (C)APD categories, respectively. The present study examines the applicability of these models to clinical practice. Neither of these models was based on data from peer-reviewed sources.

Method

This is a retrospective study that reviewed 178 records of children diagnosed with (C)APD, of which 48 were retained for analysis.

Results

More than 80% of the children could be classified into one of the Buffalo Model categories, while more than 90% remained unclassified under the Bellis/Ferre Model. This discrepancy can be explained by the fact that the classification of the Buffalo Model is based primarily on a single central auditory test (Staggered Spondaic Word), whereas the Bellis/Ferre Model classification uses a combination of auditory test results.

Conclusion

The 2 models provide a conceptual framework for (C)APD, but they must be further refined to be fully applicable in clinical settings.

Can children with (central) auditory processing disorders ignore irrelevant sounds?

This study investigated the effects of irrelevant sounds on the serial recall performance of visually presented digits in a sample of children diagnosed with (central) auditory processing disorders [(C)APD] and age- and span-matched control groups. The irrelevant sounds used were samples of tones and speech. Memory performance was significantly disrupted in the presence of irrelevant sounds in all three groups of children. While irrelevant speech was more disruptive than irrelevant tones in the two control groups, children diagnosed with (C)APD did not show larger disruption from irrelevant speech compared to irrelevant tones. Children diagnosed with (C)APD appear to process speech differently from their typically developing peers, and this may be remediated with auditory training procedures and the placement of these children in smaller classes.

The development of the text reception threshold test: a visual analogue of the speech reception threshold test

PURPOSE

In this study, the authors aimed to develop a visual analogue of the widely used Speech Reception Threshold (SRT; R. Plomp & A. M. Mimpen, 1979b) test. The Text Reception Threshold (TRT) test, in which visually presented sentences are masked by a bar pattern, enables the quantification of modality-aspecific variance in speech-in-noise comprehension to obtain more insight into interindividual differences in this ability.

METHOD

Using an adaptive procedure similar to the SRT test, the TRT test determines the percentage of unmasked text needed to read 50% of sentences correctly. SRTs in stationary noise (SRT(STAT)), modulated noise (SRT(MOD)), and TRTs were determined for 34 participants with normal hearing, aged 19 to 78 years.

RESULTS

The results indicate that about 30% of the variance in SRT(STAT) and SRT(MOD) is shared with variance in TRT, which reflects the shared involvement of a modality-aspecific cognitive or linguistic ability in forming meaningful wholes of fragments of sentences.

CONCLUSION

The TRT test, a visual analogue of the SRT test, has been developed to measure the variance in speech-in-noise comprehension associated with modality-aspecific cognitive skills. In future research, normative data of the TRT test should be developed. It would also be interesting to measure TRTs of individuals experiencing difficulties understanding speech.

Auditive Verarbeitungs- und Wahrnehmungsstörungen (AVWS)

BACKGROUND

Disorders in auditory processing have gained importance over the past 10 years. A first consensus statement defined this disorder and described several of its features. At the present stage of research, tests are missing to discriminate between normal and disturbed auditory processing development.

MATERIAL AND METHODS

A total of 142 children from the second and third grades (105 control group, 37 patients) were examined for audiological, auditory and cognitive development, as well as speech and writing abilities.

RESULTS

For the first time, normative data were defined for children from 8-9 years of age, and characteristic aspects of auditory processing disorder (APD) could be quantified.

CONCLUSION

This study supplies a test-battery with important elements for diagnosing APD under defined conditions.

Auditory speech recognition and visual text recognition in younger and older adults: similarities and differences between modalities and the effects of presentation rate

PURPOSE

To examine age-related differences in auditory speech recognition and visual text recognition performance for parallel sets of stimulus materials in the auditory and visual modalities. In addition, the effects of variation in rate of presentation of stimuli in each modality were investigated in each age group.

METHOD

A mixed-model design was used in which 3 independent groups (13 young adults with normal hearing, 10 elderly adults with normal hearing, and 16 elderly hearing-impaired adults) listened to auditory speech tests (a sentence-in-noise task, time-compressed monosyllables, and a speeded-spelling task) and viewed visual text-based analogs of the auditory tests. All auditory speech materials were presented so that the amplitude of the speech signal was at least 15 dB above threshold through 4000 Hz.

RESULTS

Analyses of the group data revealed that when baseline levels of performance were used as covariates in the group analyses the only significant group difference was that both elderly groups performed worse than the young group on the auditory speeded-speech tasks. Analysis of individual data, using correlations, factor analysis, and linear regression, was generally consistent with the group data and revealed significant, moderate correlations of performance for similar tasks across modalities, but stronger correlations across tasks within a modality. This suggests that performance on these tasks was mediated both by a common underlying factor, such as cognitive processing, as well as modality-specific processing.

CONCLUSION

Performance on measures of auditory processing of speech examined here was closely associated with performance on parallel measures of the visual processing of text obtained from the same participants. Young and older adults demonstrated comparable abilities in the use of contextual information in each modality, but older adults, regardless of hearing status, had more difficulty with fast presentation of auditory speech stimuli than young adults. There were no differences among the 3 groups with regard to the effects of presentation rate for the visual recognition of text, at least for the rates of presentation used here.

The importance of modality specificity in diagnosing central auditory processing disorder

PURPOSE

This article argues for the use of modality specificity as a unifying framework by which to conceptualize and diagnose central auditory processing disorder (CAPD). The intent is to generate dialogue and critical discussion in this area of study.

METHOD

Research in the cognitive, behavioral, and neural sciences that relates to the concept of modality specificity was reviewed and synthesized.

RESULTS

Modality specificity has a long history as an organizing construct within a diverse collection of mainstream scientific disciplines. The principle of modality specificity was contrasted with the unimodal inclusive framework, which holds that auditory tests alone are sufficient to make the CAPD diagnosis. Evidence from a large body of data demonstrated that the unimodal framework was unable to delineate modality-specific processes from more generalized dysfunction; it lacked discriminant validity and resulted in an incomplete assessment. Consequently, any hypothetical model resulting from incomplete assessments or potential therapies that are based on indeterminate diagnoses are themselves questionable, and caution should be used in their application.

CONCLUSIONS

Improving specificity of diagnosis is an imperative core issue to the area of CAPD. Without specificity, the concept has little explanatory power. Because of serious flaws in concept and design, the unimodal inclusive framework should be abandoned in favor of a more valid approach that uses modality specificity.

Can Central Auditory Processing Tests Resist Supramodal Influences?

For the past 10 years, Cacace and McFarland have contended that current central auditory processing tests are invalid because they cannot disassociate central auditory processing disorder (CAPD) from language, attention, and other problems. Over this period of time, they have not developed a battery of tests to compare with the current procedures, so the question cannot be resolved in a proper scientific fashion. Also, we disagree with their contention and demonstrate that an experienced audiologist, under double-blind research conditions, can reliably evaluate individuals with attention-deficit/hyperactivity disorder for CAPD, whether therapeutically controlled for attention with Ritalin or taking a placebo. Further, we show how intra- and intertest comparisons, as well as a team approach, disassociate CAPD from potential contamination from supramodal factors.

Nonmodularity of the Central Auditory Nervous System

This response to A. T. Cacace and D. J. McFarland (2005) identifies points of agreement and disagreement regarding the concept of modularity in the diagnosis of (central) auditory processing disorder [(C)APD]. We concur that the evaluation of (C)APD must take into consideration the influence of higher order global or pansensory issues on performance on tests of central auditory function. To accomplish this goal, multidisciplinary (e.g., multimodal) testing is an integral part of differential diagnosis of (C)APD. We also agree that the efficiency of diagnostic tests of (C)APD should not be evaluated by imprecise criteria [e.g., "presumed" or "suspected" (C)APD], which do not provide accurate measures of the true sensitivity and specificity of these tests. Our conceptualization and recommendations for clinical practice in this area diverge, however, from that of Cacace and McFarland in a number of pivotal ways. Based on the current limitations of multimodal assessment relative to issues related to scope of practice and test efficiency, as well as the accumulated basic science and clinical literature that demonstrates the nonmodularity and interactive organization of the brain, we recommend use of the sensitized test battery of the central auditory nervous system (CANS) in combination with multidisciplinary testing to differentially diagnose (C)APD and to guide treatment of the disorder. We assert that sensitivity and specificity measures derived from individuals with well-circumscribed lesions of the CANS provide an important guide to establishing the validity of central auditory diagnostic tests. We note that researchers in the area of auditory science and (C)APD must acknowledge the challenges of the clinical arena, and we encourage their continued help to develop diagnostic tools that are both efficient and practical for the differential diagnosis of (C)APD. We conclude that our approach, which combines multidisciplinary evaluation and specific tests of central auditory function that have demonstrated sensitivity and specificity for disorders of the CANS, allows us to identify (and thus rehabilitate) the auditory deficits present in individuals with (C)APD in its "purest" form. It also permits the identification and rehabilitation of auditory deficits in individuals who exhibit auditory perceptual problems that coexist with other processing problems, while ruling out those who perform poorly on auditory tests because of a global, supramodal problem involving cognition, attention, language, memory, or related skills.

Do ???Auditory Processing??? Tests Measure Auditory Processing in the Elderly?

OBJECTIVE

To examine the associations between measures of auditory processing and measures of auditory or cognitive function in elderly listeners with impaired hearing.

DESIGN

Multiple measures of auditory processing, auditory function, and cognitive function were obtained and linear, multiple-regression analyses were conducted to examine the relations between these sets of variables. In particular, four measures of auditory processing were obtained from each of 213 elderly participants. Measures of auditory processing included duration discrimination for a 1000-Hz pure tone, temporal-order discrimination for mid-frequency pure tones, dichotic syllable identification, and recognition of 45% time-compressed monosyllables. Each participant also completed additional measures of auditory function, including pure-tone thresholds, auditory brain stem responses for each ear and at two presentation rates (11.1 and 71.1 clicks per second), and performance-intensity functions for monosyllabic words (PI-PB rollover). Finally, three measures of cognitive function, all from the Wechsler Adult Intelligence Scale-Revised, were obtained from the 213 participants.

RESULTS

For three of the four measures of auditory processing examined in this study (duration discrimination, temporal-order discrimination, and dichotic CV identification), a measure of cognitive function (IQ) and age were the two primary predictors of individual differences in performance. For these three measures of auditory processing, 11 to 14% of the total variance could be accounted for by the predictor variables. For the remaining measure of auditory processing (recognition of time-compressed monosyllables), 56% of the total variance could be accounted for by a set of four predictor variables, but most of this variance (54% of the total variance) was associated with individual differences in hearing loss. When hearing loss was removed as a predictor for this measure of auditory processing, 14% of the total variance was explained by four variables: age, IQ, and two measures derived from auditory brain stem response wave-V latency.

CONCLUSIONS

Performance on the battery of auditory processing measures by elderly hearing-impaired listeners was systematically related to individual differences in cognitive function rather than auditory function, especially for stimuli not affected by peripheral hearing loss. However, much of the variance in auditory processing performance remained unaccounted for by any of the predictor variables examined in this study.

Frequency discrimination deficits in people with specific language impairment: reliability, validity, and linguistic correlates

The reliability and validity of a frequency discrimination (FD) task were tested in 16 people with specific language impairment (SLI) and 16 people with normal spoken language (controls). The FD thresholds of the 2 groups indicated that FD thresholds for 25-ms and 250-ms tones were remarkably stable across 18 months. The FD thresholds were lower for control listeners than for listeners with SLI for both duration conditions, and the FD thresholds for both groups of listeners were lower for 250-ms tones than for 25-ms tones. Moreover, the FD thresholds were influenced little by nonperceptual, task-related abilities (e.g., paired-associative learning, memory for temporal order, sustained attention, and control of attention) of the listener groups. The significant group difference between the mean FD thresholds of the SLI and control groups was explained by a subgroup of people with SLI who had particularly poor thresholds compared with those of controls and the majority of the SLI group. This subgroup did not differ from the remainder of the SLI sample in terms of age or nonverbal ability but was characterized by very poor reading that was associated with poor phonemic awareness.

Age effects and normative data on a Dutch test battery for auditory processing disorders

A test battery compiled to diagnose auditory processing disorders (APDs) in an adult population was used on a population of 9-16-year-old children. The battery consisted of eight tests (words -in noise, filtered speech, binaural fusion, dichotic digits, frequency and duration patterns, backward masking, categorical perception, digit span) and a questionnaire. Descriptive statistics were computed on data obtained from 75 children from primary school (age 9-12 years) and 30 adolescents from secondary school (age 14-16 years) with normal hearing and normal intelligence. Most test scores did not follow a normal distribution. Age effects were present in most tests, within the group as well as when children and adolescents were compared to adults. This suggests that maturation of auditory processing abilities takes place even during adolescence. Relative measures regarding ear differences and binaural versus monaural scores did not appear to be age-related. These measures might be useful in diagnosing APD, supplementary to the absolute measures. Factor analysis showed four components that address underlying processes. However, these results must be interpreted cautiously because the study did not include any subjects with APD.

Deciphering auditory processing disorders in children

APD is not a label for a unitary disease entity but rather a description of functional deficits [3]. It is a complex and heterogeneous group of auditory-specific disorders usually associated with a range of listening and learning deficits [3,4]. Underlying APD is a deficit observed in one or more of the auditory processes responsible for generating the auditory evoked potentials and the following behaviors: around localization and lateralization; auditory discrimination; auditory pattern recognition; temporal aspects of audition, including temporal resolution, masking, integration, and ordering; auditory performance with competing acoustic signals; and auditory performance with degraded acoustic signals [2]. Comprehensive assessment is necessary for the accurate differential diagnosis of APD from other "look-alike" disorders, most notably ADHD and language processing disorders. Speech-language pathologists, psychologists, educators, and physicians contribute to this more comprehensive assessment. The primary role of otolaryngologists is to evaluate and treat peripheral hearing disorders, such as otitis media. Children with APDs may present to an otolaryngologist, thus requiring the physician to make appropriate referral for assessment and intervention. Currently, diagnosis of APD is based on the outcomes of behavioral tests, supplemented by electroacoustic measures and, to a lesser extent, by electrophysiologic measures [1]. Intervention for APD focuses on improving the quality of the acoustic signal and the listening environment, improving auditory skills, and enhancing utilization of metacognitive and language resources [2]. Additional controlled case studies and single-subject and group research designs are needed to ascertain systematically the relative efficacy of various treatment and management approaches.

A new CAPD battery--multiple auditory processing assessment: factor analysis and comparisons with SCAN

Based on recommendations by Musiek & Chermak (1994, American Journal of Audiology, 3, 23-27) and ASHA (1996, American Journal of Audiology, 5(2), 41-54), a battery of four commonly used tests was selected and recorded for use in assessing school children. These tests were labeled the Multiple Auditory Processing Assessment (MAPA) and then administered to an initial sample of 81 third grade children, along with the SCAN screening test for auditory processing disorders. Afterward, several exploratory factor analyses were performed on the findings, and comparisons were made between the results for the MAPA and SCAN. Four separate factors emerged from the four MAPA tests, which were linked closely to the components of central auditory processing disorders (CAPDs) defined by ASHA (1996, American Journal of Audiology, 5(2), 41-54). These factors were labeled monaural separation/closure (MSC), auditory pattern/temporal ordering, binaural integration, and binaural separation (BS). SCAN appears to measure two of these factors, MSC and BS. Use of MAPA is encouraging. Our findings suggest it may provide an appropriate multiple-test, CAPD battery for third grade children, and it meets at least some of the objectives described in the consensus document proposed by ASHA (1996, American Journal of Audiology, 5(2), 41-54).

Implications from factor analysis for central auditory processing disorders

Central auditory processing disorders among school-age children have been challenging to identify and treat. Many issues remain that need to be resolved. Here, we compare and contrast findings on 331 school-age children who were given two of the more common central auditory processing disorder tests (Staggered Spondaic Word [SSW] Test and the SCAN Screening Test for Auditory Processing Disorders). These results replicate and reinforce many of the psychometric findings reported earlier. The use of factor analysis with these test results was explored. Significantly, two factors emerged, including an auditory binaural separation from competition factor and a monaural low redundancy degradation factor. These findings help us define the nature of processes probed by the SCAN screening test and the SSW test. Furthermore, these findings clarify the use of SSW and SCAN because they showed both SSW Left Competing and Right Competing loading within the same factor, whereas the three subtests on SCAN sorted into two rather than three factors.

Clinical Decision-Making in the Assessment and Intervention of Central Auditory Processing Disorders

Central auditory processing disorders (CAPDs) are fraught with problems arising from confusion concerning the clinical evidence of the disorder. A major controversy revolves around characterizing the disorder as a unique cluster of behaviors reflecting impairment in some underlying mechanism(s) or as a disorder defined on the basis of performance on a set of tests. This article reviews some recent developments in auditory processing research and considers the role of the speech-language pathologist in evaluating and treating children with suspected auditory processing problems. Particular attention is given to clinical criteria, including characteristics of the population, assessment, and intervention considerations. Areas for clinical caution are highlighted.

SCAN test-retest reliability for first- and third-grade children

The SCAN is a popular screening test that was developed to provide a rapidly administered, standardized method for determining the potential of central auditory processing disorder (CAPD) in children between the ages of 3 and 11 years. It can be administered in 20 minutes with a portable stereo cassette player and contains three subtests: filtered words (FW), auditory figure ground (AFG), and competing words (CW). Published SCAN test-retest reliability data (Keith, 1986) used a 6-month retest interval and indicated that SCAN scores may be unreliable. No additional reliability data are available, and studies indicate that SCAN has been used by both researchers and clinicians despite reliability concerns. This investigation examined the stability of SCAN outcomes for 25 first-grade and 22 third-grade children (ages 6 to 9 years) using a 6- to 7-week retest interval. Time of day and examiner were held constant, and participants were normal-hearing, were Caucasian, and spoke English as their primary language. ANOVA outcomes indicated that both raw and standard scores improved significantly from Test 1 to Test 2 for two of the three SCAN subtests (FW and CW) and for the composite (COMP) score. Additionally, COMP-percentile-rank and age-equivalent outcomes demonstrated significant improvement from test to retest for both grades. The AFG subtest was the only SCAN measure for which a significant test-retest difference did not emerge. The highest test-retest correlation values (r) were moderately strong (0.70 < or = r < or = 0.78) and occurred for the CW and COMP scores. Implications of correlations and factor analyses are discussed. It is suggested that examiners base recommendations for additional testing, follow up, and remediation on the COMP score only. Further, it appears that second administration of the SCAN can provide a better estimate of an individual child's best performance, but lack of second-score norms confounds simple interpretation of such scores.

Central auditory processing disorder in school-aged children: a critical review

The rationale to evaluate for central auditory processing disorder (CAPD) in school-aged children is based on the assumption that an auditory-specific perceptual deficit underlies many learning problems including specific reading and language disabilities. A fundamental issue in this area is whether convincing empirical evidence exists to validate this proposition. Herein, we consider the issue of modality specificity by examining the extent to which reading, language, and attention disorders in school-aged children involve perceptual dysfunctions limited to a single sensory modality. Difficulty in validating CAPD as a diagnostic label is due in large part to use of the unimodal inclusive framework, which has biased the diagnosis to favor sensitivity of test results over documenting the specificity of the deficit. Indeed, empirical research documenting modality-specific auditory-perceptual dysfunction in this population is scarce. Therefore, the existing literature on this topic has not clarified the "true" nature of the problem, and has left many questions about this disorder unanswered. It is argued that demonstrating modality specificity is one way to rule out supramodal disorders as explanations for observed dysfunction. Multimodal perceptual testing is one logical approach to help clarify this area of investigation.

Modality specificity of auditory and visual pattern recognition: implications for the assessment of central auditory processing disorders

We determined the degree of overlap in required processing resources between simultaneously performed non-verbal auditory and visual pattern-recognition tasks. In experiment 1, concurrent presentation of binary auditory frequency pattern sequences interfered with recognition memory of both binary auditory sound pressure level and binary color sequences, but the amount of interference was greater with auditory-level patterns. In experiment 2, mutual interference was demonstrated between auditory level and visual color pattern sequences. We conclude that dual-task performance using auditory and visual pattern-recognition tasks is limited by modality-specific perceptual factors and by modality-independent cognitive factors not specific to a single sensory modality. It is concluded that poor performance on a single pattern-recognition task cannot be associated in a one-to-one fashion with a single perceptual ability or process.