Auditory processing theories of language disorders: past, present, and future

Atypical function of auditory sensory gating in children with developmental dyslexia: Investigating its relationship with cognitive abilities

Impairments of auditory processing are among frequent findings in dyslexia. However, it is unclear how auditory signals are gated from brainstem to higher central processing stages in these individuals. The present study was done to investigate auditory sensory gating in children with developmental dyslexia (DD), and to determine whether sensory gating correlates with performance on behavioural tasks. Auditory sensory gating at P50, N1 and P2 waves was evaluated in two groups including 20 children with DD and 19 children with typical reading development (TRD). Behavioural tests were used to evaluate phonological working memory (PWM) and selective attention abilities. Sensory gating in children with DD was significantly less efficient than their peers at P50, N1 and P2 waves. Lower auditory evoked potential (AEP) amplitudes were found in the DD group. The children with TRD scored better in all the behavioural tests. Relationships were reported between sensory gating at P50, N1, P2 and behavioural performance in the two groups. Children with dyslexia had deficient sensory gating in comparison with controls. In addition, children with dyslexia experienced problems with PWM and selective attention tasks. The function of sensory gating was associated with attentional and PWM performances in this group.

Brainstem auditory physiology in children with listening difficulties. Hear Res 2023;429:108705. [PMID: 36709582 PMCID: PMC10152893 DOI: 10.1016/j.heares.2023.108705]

Children who have listening difficulties (LiD) despite having normal audiometry are often diagnosed as having an auditory processing disorder. A lack of evidence regarding involvement of specific auditory mechanisms has limited development of effective treatments for these children. Here, we examined electrophysiologic evidence for brainstem pathway mechanisms in children with and without defined LiD. We undertook a prospective controlled study of 132 children aged 6-14 years with normal pure tone audiometry, grouped into LiD (n = 63) or Typically Developing (TD; n = 69) based on scores on the Evaluation of Children's Listening and Processing Skills (ECLiPS), a validated caregiver report. The groups were matched on age at test, sex, race, and ethnicity. Neither group had diagnoses of major neurologic disorder, intellectual disability, or brain injuries. Both groups received a test battery including a measure of receptive speech perception against distractor speech, Listening in Spatialized Noise - Sentences (LiSN-S), along with multiple neurophysiologic measures that tap afferent and efferent auditory subcortical pathways. Group analysis showed that participants with LiD performed significantly poorer on all subtests of the LiSN-S. The LiD group had significantly greater wideband middle ear muscle reflex (MEMR) growth functions in the left ear, and shorter Wave III and Wave V latencies in auditory brainstem responses (ABR). Across individual participants, shorter latency ABR Wave V correlated significantly with poorer parent report of LiD (ECLiPS composite). Greater MEMR growth functions also correlated with poorer ECLiPS scores and reduced LiSN-S talker advantage. The LiD and TD groups had equivalent summating potentials, compound action potentials, envelope-following responses, and binaurally activated medial olivocochlear reflexes. In conclusion, there was no evidence for auditory synaptopathy for LiD. Evidence for brainstem differences in the LiD group was interpreted as increased central gain, with shorter ABR Wave III and V latencies and steeper MEMR growth curves. These differences were related to poorer parent report and speech perception in competing speech ability.

Developmental Language Disorder Is Associated With Slower Processing Across Domains: A Meta-Analysis of Time-Based Tasks

PURPOSE

Individuals with developmental language disorder (DLD) often exhibit slower processing on time-based tasks in comparison with age-matched peers. Processing speed has been linked to various linguistic skills and might serve as a global indicator of individual differences in language abilities. Despite an extensive literature on processing speed in DLD, it remains unclear whether slower processing is domain general or restricted to linguistic and/or auditory tasks.

METHOD

This meta-analysis used robust variance estimation to compare response/reaction times (RTs) of DLD and age-matched groups (N = 812 DLD, 870 neurotypical; M _age [DLD] = 8.9 years, range: 4.3-22.7 years). Moderators included task (simple RT, choice RT, naming, congruent/baseline conditions of interference control tasks), stimulus type (linguistic/nonlinguistic), stimulus modality (auditory/nonauditory), and response modality (verbal/nonverbal). Age and publication year were covariates.

RESULTS

The overall effect based on 46 studies and 144 estimates indicated longer mean RTs in DLD groups (g = .47, p < .001, 95% CI [.38, .55]). Moderator analyses indicated larger effects when tasks required verbal as opposed to nonverbal responses. No other moderators approached significance. All subgroup analyses were significant, indicating longer mean RTs in DLD groups across tasks, stimulus types, stimulus modalities, and response modalities.

CONCLUSIONS

Individuals with DLD exhibit longer RTs across verbal and nonverbal tasks, which may contribute to observed difficulties in language, motor skills, and executive functioning. Simple processing speed measures should be included in screening for language delays but may not be suitable for differential diagnosis, given that slower processing may occur across multiple disorders.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21809355.

Auditory processing disorder evaluations and cognitive profiles of children with specific learning disorder

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Children with altered auditory processing exhibit a specific cognitive profile.

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Lower verbal and spatial reasoning performance are associated with altered auditory processing.

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Children with specific learning disorder should undergo a complete multimodal examination.

Objective

This study investigated the auditory sensory-perceptual level of specific learning disorder (SLD) and explored relationships among neuropsychological assessments for SLD, auditory processing, and short and long latencies of auditory event-related potentials (ERPs).

Methods

Fifteen children (7–14 years old) comprised the control group; 34 children comprised the SLD group. Audiologic assessments included tone audiometry, acoustic immittance measurements, acoustic reflex, central auditory processing, brainstem evoked response audiometry, and long latency potentials (P3 and N2). Children’s intelligence levels were assessed with 2 intelligence batteries, 1 verbal and 1 non-verbal, as well as with visuomotor skills.

Results

Multiple regression showed a significant interaction effect of APE tests and P3/N2 over Wechsler Scale performance in freedom of distractibility indexes and multiple subtests. Errors in the Bender Visual Motor Gestalt Test were predicted by lower parental education, lower performance in APE tests: dichotic digits and pediatric/synthetic sentence identification-ipsilateral, and longer P3/N2 latencies, particularly regarding integration and rotation distortions.

Conclusions

Children with altered auditory processing exhibit a specific cognitive profile, including lower verbal and spatial reasoning performance, that is sensitive to parental education level.

Significance

Children with SLD should undergo a complete multimodal examination to identify their specific difficulties and needs.

Speech profiles of Spanish-Catalan children with developmental language disorder

Children with developmental language disorders (DLD) are especially characterised by morphosyntactic difficulties. Nevertheless, previous studies have also shown that children with DLD have phonological difficulties. This paper aims to describe the productive and perceptive phonological speech profile of Spanish-Catalan children with DLD at the age of six in order to characterise the underlying nature of their difficulties. Fourteen Spanish-Catalan six-year-old children with DLD and 14 control children without language difficulties who attended the same class were assessed with the screening and discrimination tasks of the A-RE-HA: Análisis del Retraso del Habla (Speech Delay Analysis - Catalan and Spanish version). We analysed the production of words, syllables and phonemes, phoneme discrimination and phonological simplification processes used by these children. The results showed that children with DLD have a lower percentile in correct word structures, syllabic structures and phonemes, and have more difficulty discriminating phonemes. Detailed analyses revealed more difficulties with the most complex word and syllabic templates, and with almost all phonemes. Furthermore, children with DLD applied more phonological simplification processes than the control group. An individual analysis showed that only ten of the children with DLD also had a speech delay (percentile < 25), while four had scores in line with their age. These results show that most of the six-year-old children with DLD maintain speech difficulties, which are mainly phonological and not (or not only) articulatory. Therefore, individual differences with respect to speech delay in DLD must be taken into consideration to better detect these children.

Same or Different: The Overlap Between Children With Auditory Processing Disorders and Children With Other Developmental Disorders: A Systematic Review

Supplemental Digital Content is available in the text.

Objectives:

Children diagnosed with auditory processing disorders (APD) experience difficulties in auditory functioning and with memory, attention, language, and reading tasks. However, it is not clear whether the behavioral characteristics of these children are distinctive from the behavioral characteristics of children diagnosed with a different developmental disorder, such as specific language impairment (SLI), dyslexia, attention-deficit hyperactivity disorder (ADHD), learning disorder (LD), or autism spectrum disorder. This study describes the performance of children diagnosed with APD, SLI, dyslexia, ADHD, and LD to different outcome measurements. The aim of this study was to determine (1) which characteristics of APD overlap with the characteristics of children with SLI, dyslexia, ADHD, LD, or autism spectrum disorder; and (2) if there are characteristics that distinguish children diagnosed with APD from children diagnosed with other developmental disorders.

Design:

A systematic review. Six electronic databases (Pubmed, CINAHL, Eric, PsychINFO, Communication & Mass Media Complete, and EMBASE) were searched to find peer-reviewed studies from 1954 to May 2015. The authors included studies reporting behaviors and performance of children with (suspected) APD and children diagnosed with a different developmental disorder (SLI, Dyslexia, ADHD, and LD). Two researchers identified and screened the studies independently. Methodological quality of the included studies was assessed with the American Speech-Language-Hearing Association’s levels-of-evidence scheme.

Results:

In total, 13 studies of which the methodological quality was moderate were included in this systematic review. In five studies, the performance of children diagnosed with APD was compared with the performance of children diagnosed with SLI: in two with children diagnosed with dyslexia, one with children diagnosed with ADHD, and in another one with children diagnosed with LD. Ten of the studies included children who met the criteria for more than one diagnosis. In four studies, there was a comparison made between the performances of children with comorbid disorders. There were no studies found in which the performance of children diagnosed with APD was compared with the performance of children diagnosed with autism spectrum disorder. Children diagnosed with APD broadly share the same characteristics as children diagnosed with other developmental disorders, with only minor differences between them. Differences were determined with the auditory and visual Duration Pattern Test, the Children’s Auditory Processing Performance Scale questionnaire, and the subtests of the Listening in Spatialized Noise-Sentences test, in which noise is spatially separated from target sentences. However, these differences are not consistent between studies and are not found in comparison to all groups of children with other developmental disorders.

Conclusions:

Children diagnosed with APD perform equally to children diagnosed with SLI, dyslexia, ADHD, and LD on tests of intelligence, memory or attention, and language tests. Only small differences between groups were found for sensory and perceptual functioning tasks (auditory and visual). In addition, children diagnosed with dyslexia performed poorer in reading tasks compared with children diagnosed with APD. The result is possibly confounded by poor quality of the research studies and the low quality of the used outcome measures. More research with higher scientific rigor is required to better understand the differences and similarities in children with various neurodevelopmental disorders.

Response to the Letter to the Editor From Moncrieff (2017) Regarding de Wit et al. (2016), "Characteristics of Auditory Processing Disorders: A Systematic Review"

PURPOSE

The purpose of this letter is to respond to Moncrieff's (2017) letter to the editor, "Response to de Wit et al., 2016, 'Characteristics of Auditory Processing Disorders: A Systematic Review,'" published in May 2017 by the Journal of Speech, Language, and Hearing Research.

CONCLUSION

We believe that our original conclusions are valid given the limited evidence that is currently available about the etiology of auditory processing disorders (APD). The focus of our systematic review was to identify the characteristics of children with a diagnosis of APD or a suspicion of APD. The results of our study showed that the characteristics of these children are not specific or limited to the auditory modality but are multimodal instead. In our view, it is incorrect to use the diagnosis APD, because there is not necessarily a specific auditory deficit in a large group of children suffering from listening difficulties. Before we start using any new diagnoses, a better insight into how bottom-up and top-down processes are precisely involved in listening needs to be developed. In addition, more insight is needed with respect to the similarities and differences between the different developmental disorders of children.

The Potential Effect of Forbrain as an Altered Auditory Feedback Device

PURPOSE

The purpose of this study was to run a proof of concept on a new commercially available device, Forbrain® (Sound For Life Ltd/Soundev, Luxemburg, model UN38.3), to test whether it can modulate the speech of its users.

METHOD

Participants were instructed to read aloud a text of their choice during 3 experimental phases: baseline, test, and posttest, while wearing a Forbrain® headset. Critically, for half of the participants (Forbrain group), the device was turned on during the test phase, whereas for the other half (control group), the device was kept off. Voice recordings were analyzed to derive 6 quantitative measures of voice quality over each of the phases of the experiment.

RESULTS

A significant Group × Phase interaction was obtained for the smoothed cepstral peak prominence, a measure of voice harmony, and for the trendline of the long-term average spectrum, a measure of voice robustness, this latter surviving Bonferroni correction for multiple comparisons.

CONCLUSIONS

The results of this study indicate the effectiveness of Forbrain® in modifying the speech of its users. It is suggested that Forbrain® works as an altered auditory feedback device. It may hence be used as a clinical device in speech therapy clinics, yet further studies are warranted to test its usefulness in clinical groups.

Screening Tests Reveal High Risk Among Adjudicated Adolescents of Auditory Processing and Language Disorders

PURPOSE

The study investigated the prevalence of risk factors for auditory processing and language disorders among adolescents residing at a local juvenile detention center.

METHOD

A total of 782 adjudicated adolescents with normal hearing were screened with the Randomized Dichotic Digits Test (Strouse & Wilson, 1999) and the Dichotic Words Test (Moncrieff, 2015). A subset of 420 of those adolescents was also screened with the Clinical Evaluation of Language Fundamentals (CELF; Semel, Wiig, & Secord, 2003).

RESULTS

More than 70% of the adolescents produced weakness on at least 1 dichotic listening test. One third of those produced weakness across both dichotic listening tests, consistent with a binaural integration deficit pattern. Nearly 48% of the subgroup of adolescents produced CELF scores that fell below the criterion for age. Dichotic listening and language scores were more associated in participants with poor performance in both ears during dichotic tests, who also produced the lowest scores on the CELF. There was no main effect of race, but 17- and 18-year-old Black adolescents produced lower CELF scores than White adolescents of the same age.

CONCLUSIONS

School-age children referred for disciplinary action may have undiagnosed deficits in auditory processing and/or language. Efforts to screen, diagnose, and remediate these deficits could lead to improvements in communication, learning, and language skills in this population.

On the Etiology of Listening Difficulties in Noise Despite Clinically Normal Audiograms

Many people with difficulties following conversations in noisy settings have “clinically normal” audiograms, that is, tone thresholds better than 20 dB HL from 0.1 to 8 kHz. This review summarizes the possible causes of such difficulties, and examines established as well as promising new psychoacoustic and electrophysiologic approaches to differentiate between them. Deficits at the level of the auditory periphery are possible even if thresholds remain around 0 dB HL, and become probable when they reach 10 to 20 dB HL. Extending the audiogram beyond 8 kHz can identify early signs of noise-induced trauma to the vulnerable basal turn of the cochlea, and might point to “hidden” losses at lower frequencies that could compromise speech reception in noise. Listening difficulties can also be a consequence of impaired central auditory processing, resulting from lesions affecting the auditory brainstem or cortex, or from abnormal patterns of sound input during developmental sensitive periods and even in adulthood. Such auditory processing disorders should be distinguished from (cognitive) linguistic deficits, and from problems with attention or working memory that may not be specific to the auditory modality. Improved diagnosis of the causes of listening difficulties in noise should lead to better treatment outcomes, by optimizing auditory training procedures to the specific deficits of individual patients, for example.

AAA (2010) CAPD clinical practice guidelines: need for an update

OBJECTIVE

Review and critique of the clinical value of the AAA CAPD guidance document in light of criteria for credible and useful guidance documents, as discussed by Field and Lohr.

DESIGN

A qualitative review of the of the AAA CAPD guidelines using a framework by Field and Lohr to assess their relative value in supporting the assessment and management of CAPD referrals.

STUDY SAMPLE

Relevant literature available through electronic search tools and published texts were used along with the AAA CAPD guidance document and the chapter by Field and Lohr.

RESULTS

The AAA document does not meet many of the key requirements discussed by Field and Lohr. It does not reflect the current literature, fails to help clinicians understand for whom auditory processing testing and intervention would be most useful, includes contradictory suggestions which reduce clarity and appears to avoid conclusions that might cast the CAPD construct in a negative light. It also does not include input from diverse affected groups. All of these reduce the document's credibility.

CONCLUSIONS

The AAA CAPD guidance document will need to be updated and re-conceptualised in order to provide meaningful guidance for clinicians.

Lexical tonal discrimination in Zapotec children. A study of the theta rhythm

BACKGROUND

Zapotec is a language used mainly in the state of Oaxaca in Mexico of tonal characteristic; homophone words with difference in fundamental frequency with different meanings. Our objective was to analyze changes in the electroencephalographic (EEG) theta rhythm during word discrimination of lexical tonal bi-syllabic homophone word samples of Zapotec.

METHODS

We employed electroencephalography analysis during lexical tonal discrimination in 12 healthy subjects 9-16 years of age.

RESULTS

We observed an increase in theta relative power between lexical discrimination and at rest eyes-open state in right temporal site. We also observed several significant intra- and inter-hemispheric correlations in several scalp sites, mainly in left fronto-temporal and right temporal areas when subjects were performing lexical discrimination.

CONCLUSIONS

Our data suggest more engagement of neural networks of the right hemisphere are involved in Zapotec language discrimination.

It Is Time to Rethink Central Auditory Processing Disorder Protocols for School-Aged Children

PURPOSE

The purpose of this article is to review the literature that pertains to ongoing concerns regarding the central auditory processing construct among school-aged children and to assess whether the degree of uncertainty surrounding central auditory processing disorder (CAPD) warrants a change in current protocols.

METHOD

Methodology on this topic included a review of relevant and recent literature through electronic search tools (e.g., ComDisDome, PsycINFO, Medline, and Cochrane databases); published texts; as well as published articles from the Journal of the American Academy of Audiology; the American Journal of Audiology; the Journal of Speech, Language, and Hearing Research; and Language, Speech, and Hearing Services in Schools.

RESULTS

This review revealed strong support for the following: (a) Current testing of CAPD is highly influenced by nonauditory factors, including memory, attention, language, and executive function; (b) the lack of agreement regarding the performance criteria for diagnosis is concerning; (c) the contribution of auditory processing abilities to language, reading, and academic and listening abilities, as assessed by current measures, is not significant; and (d) the effectiveness of auditory interventions for improving communication abilities has not been established.

CONCLUSIONS

Routine use of CAPD test protocols cannot be supported, and strong consideration should be given to redirecting focus on assessing overall listening abilities. Also, intervention needs to be contextualized and functional. A suggested protocol is provided for consideration. All of these issues warrant ongoing research.

Auditory processing disorders with and without central auditory discrimination deficits

Auditory processing disorder (APD) is defined as a processing deficit in the auditory modality and spans multiple processes. To date, APD diagnosis is mostly based on the utilization of speech material. Adequate nonspeech tests that allow differentiation between an actual central hearing disorder and related disorders such as specific language impairments are still not adequately available. In the present study, 84 children between 6 and 17 years of age (clinical group), referred to three audiological centers for APD diagnosis, were evaluated with standard audiological tests and additional auditory discrimination tests. Latter tests assessed the processing of basic acoustic features at two different stages of the ascending central auditory system: (1) auditory brainstem processing was evaluated by quantifying interaural frequency, level, and signal duration discrimination (interaural tests). (2) Diencephalic/telencephalic processing was assessed by varying the same acoustic parameters (plus signals with sinusoidal amplitude modulation), but presenting the test signals in conjunction with noise pulses to the contralateral ear (dichotic(signal/noise) tests). Data of children in the clinical group were referenced to normative data obtained from more than 300 normally developing healthy school children. The results in the audiological and the discrimination tests diverged widely. Of the 39 children that were diagnosed with APD in the audiological clinic, 30 had deficits in auditory performance. Even more alarming was the fact that of the 45 children with a negative APD diagnosis, 32 showed clear signs of a central hearing deficit. Based on these results, we suggest revising current diagnostic procedure to evaluate APD in order to more clearly differentiate between central auditory processing deficits and higher-order (cognitive and/or language) processing deficits.

Early preschool processing abilities predict subsequent reading outcomes in bilingual Spanish-Catalan children with Specific Language Impairment (SLI)

Children with Specific Language Impairment (SLI) have severe language difficulties without showing hearing impairments, cognitive deficits, neurological damage or socio-emotional deprivation. However, previous studies have shown that children with SLI show some cognitive and literacy problems. Our study analyses the relationship between preschool cognitive and linguistic abilities and the later development of reading abilities in Spanish-Catalan bilingual children with SLI. The sample consisted of 17 bilingual Spanish-Catalan children with SLI and 17 age-matched controls. We tested eight distinct processes related to phonological, attention, and language processing at the age of 6 years and reading at 8 years of age. Results show that bilingual Spanish-Catalan children with SLI show significantly lower scores, as compared to typically developing peers, in phonological awareness, phonological memory, and rapid automatized naming (RAN), together with a lower outcome in tasks measuring sentence repetition and verbal fluency. Regarding attentional processes, bilingual Spanish-Catalan children with SLI obtained lower scores in auditory attention, but not in visual attention. At the age of 8 years Spanish-Catalan children with SLI had lower scores than their age-matched controls in total reading score, letter identification (decoding), and in semantic task (comprehension). Regression analyses identified both phonological awareness and verbal fluency at the age of 6 years to be the best predictors of subsequent reading performance at the age of 8 years. Our data suggest that language acquisition problems and difficulties in reading acquisition in bilingual children with SLI might be related to the close interdependence between a limitation in cognitive processing and a deficit at the linguistic level.

LEARNING OUTCOMES

After reading this article, readers will be able to: identify their understanding of the relation between language difficulties and reading outcomes; explain how processing abilities influence reading performance in bilingual Spanish-Catalan children with SLI; and recognize the relation between language and reading via a developmental model in which the phonological system is considered central for the development of decoding abilities and comprehension.

When words fail us: insights into language processing from developmental and acquired disorders

Acquired disorders of language represent loss of previously acquired skills, usually with relatively specific impairments. In children with developmental disorders of language, we may also see selective impairment in some skills; but in this case, the acquisition of language or literacy is affected from the outset. Because systems for processing spoken and written language change as they develop, we should beware of drawing too close a parallel between developmental and acquired disorders. Nevertheless, comparisons between the two may yield new insights. A key feature of connectionist models simulating acquired disorders is the interaction of components of language processing with each other and with other cognitive domains. This kind of model might help make sense of patterns of comorbidity in developmental disorders. Meanwhile, the study of developmental disorders emphasizes learning and change in underlying representations, allowing us to study how heterogeneity in cognitive profile may relate not just to neurobiology but also to experience. Children with persistent language difficulties pose challenges both to our efforts at intervention and to theories of learning of written and spoken language. Future attention to learning in individuals with developmental and acquired disorders could be of both theoretical and applied value.

Postnatal development of auditory central evoked responses and thalamic cellular properties

During development, the sense of hearing changes rapidly with age, especially around hearing onset. During this period, auditory structures are highly sensitive to alterations of the acoustic environment, such as hearing loss or background noise. This sensitivity includes auditory temporal processing, which is important for processing complex sounds, and for acquiring reading and language skills. Developmental changes can be observed at multiple levels of brain organization-from behavioral responses to cellular responses, and at every auditory nucleus. Neuronal properties and sound processing change dramatically in auditory cortex neurons after hearing onset. However, development of its primary source, the auditory thalamus, or medial geniculate body (MGB), has not been well studied over this critical time window. Furthermore, to understand how temporal processing develops, it is important to determine the relative maturation of temporal processing not only in the MGB, but also in its inputs. Cellular properties of rat MGB neurons were studied using in vitro whole-cell patch-clamp recordings, at ages postnatal day (P) 7-9; P15-17, and P22-32. Auditory evoked potentials were measured in P14-17 and P22-32 rats. MGB action potentials became about five times faster, and the ability to generate spike trains increased with age, particularly at frequencies of 50 Hz and higher. Evoked potential responses, including auditory brainstem responses (ABR), middle latency responses (MLR), and amplitude modulation following responses, showed increased amplitudes with age, and ABRs and MLRs additionally showed decreased latencies with age. Overall, temporal processing at subthalamic nuclei is concurrently maturing with MGB cellular properties.

Listening difficulties in children: bottom-up and top-down contributions

The brain mechanisms of hearing include large regions of the anterior temporal, prefrontal, and inferior parietal cortex, and an extensive network of descending connections between the cortex and sub-cortical components of what is presently known as the auditory system. One important function of these additional ('top-down') mechanisms for hearing is to modulate the ascending, sensory ('bottom-up') auditory information from the ear. In children, normal, immature hearing during the first decade of life is more strongly influenced by top-down mechanisms than in adulthood. In some children, impaired top-down function presents a significant challenge to their auditory perception, often associated with a range of language and learning difficulties and sometimes called auditory processing disorder.

Auditory Training for Children With Auditory Processing Disorder and Language Impairment: A Response to Bellis, Chermak, Weihing, and Musiek

Purpose

We respond to Bellis, Chermak, Weihing, and Musiek’s (2012) criticisms of the evidence-based systematic review of Fey et al. (2011) on the effects of auditory training on auditory, spoken, and written language performance of children with auditory processing disorder or language impairment. In general, we argue that the conceptualizations and methods on which our review was based were well motivated, and that our original conclusions are valid given the limited evidence that is currently available from clinical studies of auditory training with school-age children with auditory processing disorder or language impairment.

Auditory deficit as a consequence rather than endophenotype of specific language impairment: electrophysiological evidence

Background

Are developmental language disorders caused by poor auditory discrimination? This is a popular theory, but behavioural evidence has been inconclusive. Here we studied children with specific language impairment, measuring the brain’s electrophysiological response to sounds in a passive paradigm. We focused on the T-complex, an event-related peak that has different origins and developmental course from the well-known vertex response.

Methods

We analysed auditory event-related potentials to tones and syllables from 16 children and 16 adolescents with specific language impairment who were compared with 32 typically-developing controls, matched for gender, IQ and age.

Results

We replicated prior findings of significant reduction in Ta amplitude for both children and adolescents with specific language impairment, which was particularly marked for syllables. The topography of the T-complex to syllables indicated a less focal response in those with language impairments. To distinguish causal models, we considered correlations between size of the Ta response and measures of language and literacy in parents as well as children. The best-fitting model was one in which auditory deficit was a consequence rather than a cause of difficulties in phonological processing.

Conclusions

The T-complex to syllables has abnormal size and topography in children with specific language impairment, but this is more likely to be a consequence rather than a cause of difficulties in phonological processing.