Sensory-based learning disability: Insights from brainstem processing of speech sounds

Speech-evoked auditory brainstem responses (speech-ABR) provide a reliable marker of learning disability in a substantial subgroup of individuals with language-based learning problems (LDs). Here we review work describing the properties of the speech-ABR in typically developing children and in children with LD. We also review studies on the relationships between speech-ABR and the commonly used click-ABR, and between speech-ABR and auditory processing at the level of the cortex. In a critical examination of previously published data, we conclude that as many as 40% of LDs have abnormal speech-ABRs and that these individuals are also likely to exhibit abnormal cortical processing. Yet, the profile of learning problems these individuals exhibit is unspecific. Leaving open the question of causality, these data suggest that speech-ABR can be used to identify a large sub-population of LDs, those with abnormal auditory physiological function. Further studies are required to determine the functional relationships among abnormal speech-ABR, speech perception, and the pattern of literacy-related and cognitive deficits in LD.     

Brainstem timing deficits in children with learning impairment may result from corticofugal origins

A substantial proportion of children with language-based learning problems [learning disabilities (LD)] display abnormal encoding of speech at rostral levels of the auditory brainstem (i.e. midbrain) as measured by the auditory brainstem response (ABR). Of interest here is whether these timing deficits originate at the rostral brainstem or whether they reflect deficient sensory encoding at lower levels of the auditory pathway. We describe the early brainstem response to speech (waves I and III) in typically developing 8- to 12-year-old children and children with LD. We then focus on the early brainstem responses in children with LD found to show abnormal components of the rostral speech-evoked ABR (waves V and A). We found that wave I was not reliably evoked using our speech stimulus and recording parameters in either typically developing children or those with LD. Wave III was reliably evoked in the large majority of subjects in both groups and its timing did not differ between them. These data are consistent with the view that the auditory deficits in the majority of LD children with abnormal speech-evoked ABR originate from corticofugal modulation of subcortical activity.     

Auditory brainstem response,middle latency response,and late cortical evoked potentials in children with learning disabilities

Auditory evoked potentials (AEPs) and behavioral tests were used to evaluate auditory processing in 10 children aged 7 to 11 years who were diagnosed as learning disabled (LD). AEPs included auditory brainstem responses (ABRs), middle latency responses (MLRs), and late cortical responses (P1, N1, P2, P3). Late cortical responses were recorded using an active listening oddball procedure. Auditory processing disorders were suspected in the LD children after a psychologist found phonologic processing and auditory memory problems. A control group of 10 age- and gender-matched children with no hearing or reported learning difficulties was also tested. Teacher ratings of classroom listening and SCAN Competing Words and Staggered Spondaic Word scores were poorer in the LD children. There were minor ABR latency differences between the two groups. Wave Na of the MLR was later and Nb was smaller in the LD group. The main differences in cortical responses were that P1 was earlier and P3 was later and smaller in the LD group.     

The effects of time compression on the auditory processing abilities of learning disabled children

This study measured the ability of ten 8- and ten 12-yr-old learning disabled (LD) children of normal intelligence (WISC-R) to discriminate phonemic contrasts in sentential stimuli (Subtest 13 of the Carrow Auditory Visual Abilities Test) presented at a 50% time-compression rate. Their group responses were compared statistically to similar data gathered earlier (May et al, J. Aud. Res., 1984, 24, 205-211) from 6-, 8-, and 10-yr-old normal children and young adults. LD Ss exhibited auditory processing capacities reminiscent of an earlier level of operation (e.g., the group of LD Ss with mn age of 12.8 yrs yielded group performance equivalent to that of normal 6- and 8-yr-olds), and also manifested marked differences in their feature- and frequency-processing abilities. These data indicate that contributing to the learning difficulties of LD children may very well be delays in auditory development and anomalies in auditory-feature processing.     

Normal and learning disabled children's central auditory processing skills: an experimental test battery

The performance of normal children (N = 13) and learning disabled children (N = 26) on an experimental battery of central auditory processing (CAP) tasks was examined. The battery included low-pass filtered speech (LPFS), binaural fusion (BF), time-compressed speech (TC), and dichotic monosyllables (DM) tests. The learning disabled subjects were classified as having normal (LD/N) or significantly impaired (LD/LD) auditory perceptual skills on the basis of a pretest battery of auditory language tests. The normal (N/N) subjects and nonauditory learning disabled (LD/N) subjects tended to perform alike across measures. The auditorily impaired (LD/LD) subjects tended to perform significantly poorer than their normal agemates. The results emphasized the heterogeneity of the learning disabled population. In addition, the results suggested a potentially useful "at risk" criterion when a CAP test battery is used in the assessment of auditory perceptual impairment among children.     

A systematic review of electrophysiological outcomes following auditory training in school-age children with auditory processing deficits

Abstract

Objective: To systematically review the peer-reviewed literature on electrophysiological outcomes following auditory training (AT) in school-age children with (central) auditory processing disorder ([C]APD). Design: A systematic review. Study sample: Searches of 16 electronic databases yielded four studies involving school-aged children whose auditory processing deficits had been confirmed in a manner consistent with and and compared to a treated and/or an untreated control group before and after AT. A further three studies were identified with one lacking a control group and two measuring auditory processing in a manner not consistent with and . Results: There is limited evidence that AT leads to measurable electrophysiological changes in children with auditory processing deficits. Conclusion: The evidence base is too small and weak to provide clear guidance on the use of electrophysiological outcomes as a measure of AT outcomes in children with auditory processing problems. The currently limited data can only be used to suggest that click-evoked AMLR and tone-burst evoked auditory P300 might be more likely to detect such outcomes in children diagnosed with (C)APD, and that speech-evoked ALLR might be more likely to detect phonological processing changes in children without a specific diagnosis of (C)APD.     

Wireless Connectivity for People with Hearing Loss: Remote Microphone Technology for Children with Hearing Loss or Auditory Processing Issues

School classrooms are noisy and reverberant environments, and the poor acoustics can be a barrier to successful learning in children, particularly those with multiple disabilities, auditory processing issues, and hearing loss. A new set of listening challenges have been imposed by the recent global pandemic and subsequent online learning requirements. The goal of this article is to review the impact of poor acoustics on the performance of children with auditory processing issues, mild hearing loss, and unilateral hearing loss. In addition, we will summarize the evidence in support of remote microphone technology by these populations.     

Auditory pathway encoding and neural plasticity in children with learning problems.

An inability to process auditory information, especially speech, characterizes many children with learning and attention problems. Our working hypothesis is that these speech-sound perception problems arise, at least in some cases, from faulty representation of the speech signal in central auditory centers. Preconscious neurophysiologic representation of sound structure by central auditory pathway neurons can be reflected by subcortical and cortical aggregate neural responses. These neurophysiologic responses can be modified by perceptual learning. Our research has shown that some children with learning problems demonstrate abnormal perception and neural representation of certain speech sounds. Differences between normal and learning-impaired groups can be attributable to aspects of neural synchrony that are reflected in aggregate neural responses. Deficiencies in neural synchrony in these children are apparent in subcortical (as well as cortical) representations of speech-sound structure, and these timing deficits are related to performance on speech-sound perception and learning measures. Moreover, impaired perception and neurophysiologic encoding of speech sounds can be improved with cue enhancement and can be modified by perceptual learning associated with auditory training.     

TEOAE suppression in adults with learning disabilities

The presentation of contralateral noise during the recording of transient evoked otoacoustic emissions (TEOAEs) reduces the amplitude of the TEOAE in normally-hearing adults. This is known as TEOAE suppression. The present study investigated TEOAE suppression in 18 adults with learning disabilities (LDs) compared to 18 adults without LDs. TEOAEs were elicited by 60 dB p.e. SPL clicks and were suppressed by the presentation of 60 dB SPL contralateral broadband noise. Suppression was measured as a change in the overall TEOAE response amplitude, and also analysed in 2-ms epochs representing different TEOAE frequency-response bands. A significant interaction was evident between group type and ear tested. Participants in the control group had right ear dominance for the suppression effect, whereas the left ear was found to be dominant for the LD group. These findings suggest a mechanism of the medial olivary cochlear bundle and efferent auditory pathway that differs in those with LD compared to those with typical learning abilities.     

TEOAE suppression in adults with learning disabilities

The presentation of contralateral noise during the recording of transient evoked otoacoustic emissions (TEOAEs) reduces the amplitude of the TEOAE in normally-hearing adults. This is known as TEOAE suppression. The present study investigated TEOAE suppression in 18 adults with learning disabilities (LDs) compared to 18 adults without LDs. TEOAEs were elicited by 60 dB p.e. SPL clicks and were suppressed by the presentation of 60 dB SPL contralateral broadband noise. Suppression was measured as a change in the overall TEOAE response amplitude, and also analysed in 2-ms epochs representing different TEOAE frequency-response bands. A significant interaction was evident between group type and ear tested. Participants in the control group had right ear dominance for the suppression effect, whereas the left ear was found to be dominant for the LD group. These findings suggest a mechanism of the medial olivary cochlear bundle and efferent auditory pathway that differs in those with LD compared to those with typical learning abilities.     

Central auditory processing in urban black children, normal and learning disabled

Normative data from Windham et al (1985) for urban Black children aged 7-10 yrs on the SSW test and the Willeford central auditory processing battery were used to compare those norms with scores of 40 children of similar age and from the same population who were referred from the Howard University Child Development Center as being at risk for learning disability (LD). The L-competing, L-non-competing, and Total Error Score indexes from the SSW test, and the L-ear score from Willeford's Competing Sentences subtest, differentiated the LD Ss as a group from normals (p less than .05). Other tests were of questionable or no value in this regard for this population. It is suggested that it would be wise to view the results of these tests with caution and preferably in connection with other audiological testing when applied to LD Ss, especially if normative data for the particular subpopulation have not been collected.     

A critical examination of vestibular function in motor-impaired learning-disabled children

This study examined the role of the vestibular system in balance and coordination problems found in motor-impaired, learning-disabled (LD) children. Vestibulo-ocular reflex (VOR) and vestibulo-spinal tests (moving platform posturography) were performed on 15 learning disabled and 54 normal children. Twelve LD children had normal VOR scores suggesting normal peripheral vestibular inputs. All 15 LD children had abnormal posturography. Motor-impaired LD children could not appropriately integrate vestibular information with visual and somatosensory inputs for postural orientation. Results suggest that the best discriminator of abnormal sensorimotor function in LD children are posturography trials requiring orientation to gravity despite absent or inaccurate visual and somatosensory cues, rather than traditionally relied on VOR and Romberg tests.     

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.     

On the relationship between speech- and nonspeech-evoked auditory brainstem responses

Auditory brainstem response (ABR) reflects activation of the neural generators along the ascending auditory pathway when a sound is heard. In this study, we explored the relationship between brainstem encoding of click and speech signals in normal-learning children and in those with language-based learning problems. To that end, ABR was recorded from both types of stimuli. We found that the normal pattern of correlation between click- and speech-evoked ABRs was disrupted when speech-evoked ABRs were delayed. Thus, delayed responses to speech were not indicative of clinically abnormal responses to clicks. We conclude that these two responses reflect largely separate neural processes and that only processes involved in encoding complex signals such as speech are impaired in children with learning problems.     

Current state of knowledge: perceptual processing by children with hearing impairment

Perception concerns the identification and interpretation of sensory stimuli in our external environment. The purpose of this review is to survey contemporary views about effects of mild to severe sensorineural hearing impairment (HI) in children on perceptual processing. The review is one of a series of papers resulting from a workshop on Outcomes Research in Children with Hearing Loss sponsored by The National Institute on Deafness and Other Communication Disorders/National Institutes of Health. Children with HI exhibit heterogeneous patterns of results. In general, however, perceptual processing of the (a) auditory properties of nonspeech reveals some problems in processing spectral information, but not temporal information; (b) auditory properties of speech reveals some problems in processing temporal sequences, variation in spatial location, and voice onset times, but not in processing talker-gender, weighting acoustic cues, or covertly orienting to the spatial location of sound; (c) linguistic properties of speech reveals some problems in processing general linguistic content, semantic content, and phonological content. The normalcy/abnormalcy of results varies as a function of degree of loss and task demands. As a general rule, children with severe HI have more abnormalities than children with mild to moderate HI. Auditory linguistic properties are also generally processed more abnormally than auditory nonverbal properties. This outcome implies that childhood HI has less effect on more physical, developmentally earlier properties that are characterized by less contingent processing. Some perceptual properties that are processed in a more automatic manner by normal listeners are processed in a more controlled manner by children with HI. This outcome implies that deliberate perceptual processing in the presence of childhood HI requires extra effort and more mental resources, thus limiting the availability of processing resources for other tasks.     

Brain stem response to speech: a biological marker of auditory processing

The auditory brain stem response to speech mimics the acoustic characteristics of the speech signal with remarkable fidelity. This makes it possible to derive from it considerable theoretical and clinically applicable information relevant to auditory processing of complex stimuli. Years of research have led to the current characterization of these neural events with respect to the underlying acoustic information they reflect. The majority of data reviewed here originates from studies using a /da/ syllable to elicit the brain stem response, which consists of transient and periodic (frequency following) neural activity. We describe how the human auditory brain stem response separately encodes source and filter characteristics of the acoustic signal, which reflects paralinguistic and linguistic information simultaneously conveyed in speech. In normal-hearing individuals, these two classes of response components (source and filter) are highly correlated within a class but not between classes. This response dissociation becomes pronounced when stimuli are presented in background noise or with faster stimulus rates. In addition, some learning-impaired children show a selective deficiency in the neural encoding of acoustic features associated with the filter characteristics of speech. These children show no deficits in the encoding of source components, further supporting the notion of separate neural mechanisms. Overall, the auditory brain stem response to speech provides a way to access subcortical auditory processing mechanisms and may be used as a biological marker of deficient sound encoding associated with learning and auditory processing disorders.     

Hearing aid fitting in children with difficulties processing auditory information-evaluation of parents' satisfaction

BACKGROUND: Some children suffer from difficulties processing auditory information despite normal cochlear function. Here we raised the question if hearing aid (HA) fitting might be beneficial for such children. METHODS: 32 children with auditory information processing deficits were fitted with HA. Three months after fitting parents were asked about individual benefits for hearing behavior using a questionnaire. RESULTS: Parents' rating indicated a significant improvement of auditory information processing after HA fitting. A high internal consistence of subscales except for loudness perception was found. CONCLUSIONS: According to the data presented it seems reasonable to assume that hearing aids may ameliorate adverse affects of auditory processing deficits. Further studies supporting these findings and possibly including an audiometric proof are warranted.     

Central auditory processing disorders and reduced motivation: three case studies

The central auditory test results for three normal-hearing children who were initially diagnosed as having a central auditory processing disorder and learning disability are presented. They were referred to the authors for second-opinion consultations. Central auditory processing retesting was performed by the authors under the condition of no reinforcement and then the condition of reinforcement with the child's favorite food, hobby, or toy. For all three cases, the central auditory test scores improved markedly bilaterally under the condition of reinforcement as compared with the condition of no reinforcement. We hypothesize that the improvement was related to increased motivation associated with the reinforcement and that these children represented false-positive results on the central auditory test battery. Large-sample studies are needed to investigate the effect of reinforcement on test performance in children with reduced central auditory test scores.     

Cognitive potential of children with attention deficit and hyperactivity disorder

The literature has described comorbidities among the symptoms of children with Attention Deficit and Hyperactivity Disorder (ADHD) and the auditory processing changes, and these symptoms have been overlooked in the assessment, and consequently, on the rehabilitation of these individuals.ObjectiveTo compare the findings of the long latency auditory evoked potentials in children with and without ADHD.MethodThis is a historical cohort cross-sectional case-control study, in which we enrolled 30 children with and without ADHD, aged 8-12 years. We performed the long-latency auditory evoked potential test in two scanning procedures through passive and active tasks differing in frequency and duration (MMNf and MMNd) (P300f and P300D).ResultsWhen comparing the performance of children with and without ADHD in the electrophysiological test assessment of hearing, we found significant differences concerning the P2 amplitude in the LE - which was higher for the ADHD group; and concerning the N2 amplitude and latency - which were abnormal in the ADHD group.ConclusionThis study provided a greater understanding of the central auditory pathways of children with and without ADHD when evaluated from electrophysiological tests.     

Deprivation-induced cortical reorganization in children with cochlear implants

A basic finding in developmental neurophysiology is that some areas of the cortex cortical areas will reorganize following a period of stimulus deprivation. In this review, we discuss mainly electroencephalography (EEG) studies of normal and deprivation-induced abnormal development of the central auditory pathways in children and in animal models.We describe age cut-off for sensitive periods for central auditory development in congenitally deaf children who are fitted with a cochlear implant. We speculate on mechanisms of decoupling and reorganization which may underlie the end of the sensitive period. Finally, we describe new magentoencephalography (MEG) evidence of somatosensory cross-modal plasticity following long-term auditory deprivation.