Impaired binaural hearing in children produced by a threshold level of middle ear disease

Variability in auditory processing performance is associated with reading difficulties rather than with history of otitis media

The nature and cause of auditory processing deficits in dyslexic individuals have been debated for decades. Auditory processing deficits were argued to be the first step in a causal chain of difficulties, leading to difficulties in speech perception and thereby phonological processing and literacy difficulties. More recently, it has been argued that auditory processing difficulties may not be causally related to language and literacy difficulties. This study compares two groups who have phonological processing impairments for different reasons: dyslexia and a history of otitis media (OM). We compared their discrimination thresholds and response variability to chronological age- and reading age-matched controls, across three auditory processing tasks: frequency discrimination, rise-time discrimination and speech perception. Dyslexic children showed raised frequency discrimination thresholds in comparison with age-matched controls but did not differ from reading age-matched controls or individuals with a history of OM. There were no group differences on speech perception or rise-time tasks. For the dyslexic children, there was an association between phonological awareness and frequency discrimination response variability, but no association with thresholds. These findings are not consistent with a 'causal chain' explanation but could be accounted for within a multiple deficits view of literacy difficulties.

Sensitivity of the antiphasic digits-in-noise test to simulated unilateral and bilateral conductive hearing loss

OBJECTIVES

The objective of this study is (1) to assess whether the presentation level of the antiphasic digits-in-noise (DIN) test affects the speech recognition threshold (SRT), (2) to evaluate how accurately simulated unilateral and bilateral conductive hearing loss is detected (CHL) and (3) to determine whether increasing the presentation level normalises the antiphasic DIN SRT.

DESIGN

Participants performed antiphasic and diotic DINs at different presentation levels with unilateral, bilateral or no earplugs.

STUDY SAMPLE

Twenty-four and twelve normal hearing adults.

RESULTS

Without earplugs, antiphasic DIN SRTs did not differ between 60 and 80 dB SPL. At 60 dB SPL, the antiphasic DIN correctly classified 92% of the unilateral earplug cases; the diotic DIN 25%. The binaural intelligibility level difference did not differ between the no-earplug condition and the condition with bilateral earplugs when the presentation was increased with the attenuation level.

CONCLUSIONS

In normal hearing participants, diotic and antiphasic DIN SRTs are independent of presentation level above a minimum level of 60 dB SPL. The antiphasic DIN is more sensitive than the diotic DIN for detecting unilateral CHL; not for bilateral CHL. The effect of CHL on DIN SRTs can be largely compensated by increasing the presentation level. Audibility plays an important role in the antiphasic and diotic DIN.

Auditory Deprivation during Development Alters Efferent Neural Feedback and Perception

Auditory experience plays a critical role in hearing development. Developmental auditory deprivation because of otitis media, a common childhood disease, produces long-standing changes in the central auditory system, even after the middle ear pathology is resolved. The effects of sound deprivation because of otitis media have been mostly studied in the ascending auditory system but remain to be examined in the descending pathway that runs from the auditory cortex to the cochlea via the brainstem. Alterations in the efferent neural system could be important because the descending olivocochlear pathway influences the neural representation of transient sounds in noise in the afferent auditory system and is thought to be involved in auditory learning. Here, we show that the inhibitory strength of the medial olivocochlear efferents is weaker in children with a documented history of otitis media relative to controls; both boys and girls were included in the study. In addition, children with otitis media history required a higher signal-to-noise ratio on a sentence-in-noise recognition task than controls to achieve the same criterion performance level. Poorer speech-in-noise recognition, a hallmark of impaired central auditory processing, was related to efferent inhibition, and could not be attributed to the middle ear or cochlear mechanics.SIGNIFICANCE STATEMENT Otitis media is the second most common reason children go to the doctor. Previously, degraded auditory experience because of otitis media has been associated with reorganized ascending neural pathways, even after middle ear pathology resolved. Here, we show that altered afferent auditory input because of otitis media during childhood is also associated with long-lasting reduced descending neural pathway function and poorer speech-in-noise recognition. These novel, efferent findings may be important for the detection and treatment of childhood otitis media.

A Study on the Reference Values and Cutoff Criteria of Masking Level Difference for Children Aged 7–12 Years

The Masking Level Difference (MLD) test is one of the main instruments for investigating binaural interaction. Studies with children aged 7–12 years still disagree about the influence of age on test performance and present discordant reference values. This study aimed to verify the effect of age on the performance of children aged 7–12 years in the MLD test and to establish reference values and cutoff criteria for this age group. Fifty-nine children with normal hearing were organized in three groups according to their age: 7–8 (n = 20), 9–10 (n = 20), and 11–12 (n = 19) years. The participants completed the MLD test by Auditec®. The Kruskal–Wallis statistical test was used to compare groups. Reference values were obtained by calculating mean, standard deviation, median, mode, and percentiles, while the cutoff criterion was obtained by subtracting two standard deviations from the mean. No statistically significant differences were observed between the groups regarding the MLD test measures. The mean MLD was 10.51 ± 1.84 dB and the cutoff point was set at 7 dB. Thus, reference values for the MLD test were established for children aged 7–12 years, who presented no effect of age on test performance.

Monaural and binaural phase sensitivity in school-age children with early-childhood otitis media

OBJECTIVE

Previous research has linked recurrent otitis media (OM) during early childhood to reduced binaural masking level differences (BMLDs) in school-age children. How this finding relates to monaural processing abilities and the individual otologic history has not been investigated systematically. The current study, therefore, addressed these issues.

DESIGN

Sensitivity to monaural and binaural phase information was assessed using a common test paradigm. To evaluate the influence of the otologic history, overall OM duration, OM onset age, and the time since the last OM episode were considered in the analyses.

STUDY SAMPLE

Children aged 6-13 years with a history of recurrent OM (N = 42) or without any previous ear diseases (N = 20).

RESULTS

Compared to the controls, the OM children showed smaller BMLDs (p < 0.05) whereas their monaural and binaural detection thresholds were comparable (p > 0.05). After controlling for age, the otologic history factors failed to predict the BMLDs of the OM children. Their monaural detection thresholds were correlated with the binaural detection thresholds (r = ∼0.5, p < 0.05) but not the BMLDs.

CONCLUSIONS

The current study suggests that early-childhood OM can impair binaural processing abilities in school-age children.

NCS Assessments of the Motor, Sensory, and Physical Health Domains

As part of the National Children's Study (NCS) comprehensive and longitudinal assessment of the health status of the whole child, scientific teams were convened to recommend assessment measures for the NCS. This manuscript documents the work of three scientific teams who focused on the motor, sensory, or the physical health aspects of this assessment. Each domain team offered a value proposition for the importance of their domain to the health outcomes of the developing infant and child. Constructs within each domain were identified and measures of these constructs proposed. Where available extant assessments were identified. Those constructs that were in need of revised or new assessment instruments were identified and described. Recommendations also were made for the age when the assessments should take place.

Minimal and Mild Hearing Loss in Children: Association with Auditory Perception, Cognition, and Communication Problems

OBJECTIVES

"Minimal" and "mild" hearing loss are the most common but least understood forms of hearing loss in children. Children with better ear hearing level as low as 30 dB HL have a global language impairment and, according to the World Health Organization, a "disabling level of hearing loss." We examined in a population of 6- to 11-year-olds how hearing level ≤40.0 dB HL (1 and 4 kHz pure-tone average, PTA, threshold) is related to auditory perception, cognition, and communication.

DESIGN

School children (n = 1638) were recruited in 4 centers across the United Kingdom. They completed a battery of hearing (audiometry, filter width, temporal envelope, speech-in-noise) and cognitive (IQ, attention, verbal memory, receptive language, reading) tests. Caregivers assessed their children's communication and listening skills. Children included in this study (702 male; 752 female) had 4 reliable tone thresholds (1, 4 kHz each ear), and no caregiver reported medical or intellectual disorder. Normal-hearing children (n = 1124, 77.1%) had all 4 thresholds and PTA <15 dB HL. Children with ≥15 dB HL for at least 1 threshold, and PTA <20 dB (n = 245, 16.8%) had minimal hearing loss. Children with 20 ≤PTA <40 dB HL (n = 88, 6.0%) had mild hearing loss. Interaural asymmetric hearing loss ( left PTA - right PTA ≥10 dB) was found in 28.9% of those with minimal and 39.8% of those with mild hearing loss.

RESULTS

Speech perception in noise, indexed by vowel-consonant-vowel pseudoword repetition in speech-modulated noise, was impaired in children with minimal and mild hearing loss, relative to normal-hearing children. Effect size was largest (d = 0.63) in asymmetric mild hearing loss and smallest (d = 0.21) in symmetric minimal hearing loss. Spectral (filter width) and temporal (backward masking) perceptions were impaired in children with both forms of hearing loss, but suprathreshold perception generally related only weakly to PTA. Speech-in-noise (nonsense syllables) and language (pseudoword repetition) were also impaired in both forms of hearing loss and correlated more strongly with PTA. Children with mild hearing loss were additionally impaired in working memory (digit span) and reading, and generally performed more poorly than those with minimal loss. Asymmetric hearing loss produced as much impairment overall on both auditory and cognitive tasks as symmetric hearing loss. Nonverbal IQ, attention, and caregiver-rated listening and communication were not significantly impaired in children with hearing loss. Modeling suggested that 15 dB HL is objectively an appropriate lower audibility limit for diagnosis of hearing loss.

CONCLUSIONS

Hearing loss between 15 and 30 dB PTA is, at ~20%, much more prevalent in 6- to 11-year-old children than most current estimates. Key aspects of auditory and cognitive skills are impaired in both symmetric and asymmetric minimal and mild hearing loss. Hearing loss <30 dB HL is most closely related to speech perception in noise, and to cognitive abilities underpinning language and reading. The results suggest wider use of speech-in-noise measures to diagnose and assess management of hearing loss and reduction of the clinical hearing loss threshold for children to 15 dB HL.

Dichotic listening deficits in amblyaudia are characterized by aberrant neural oscillations in auditory cortex

OBJECTIVE

Children diagnosed with auditory processing disorder (APD) show deficits in processing complex sounds that are associated with difficulties in higher-order language, learning, cognitive, and communicative functions. Amblyaudia (AMB) is a subcategory of APD characterized by abnormally large ear asymmetries in dichotic listening tasks.

METHODS

Here, we examined frequency-specific neural oscillations and functional connectivity via high-density electroencephalography (EEG) in children with and without AMB during passive listening of nonspeech stimuli.

RESULTS

Time-frequency maps of these "brain rhythms" revealed stronger phase-locked beta-gamma (~35 Hz) oscillations in AMB participants within bilateral auditory cortex for sounds presented to the right ear, suggesting a hypersynchronization and imbalance of auditory neural activity. Brain-behavior correlations revealed neural asymmetries in cortical responses predicted the larger than normal right-ear advantage seen in participants with AMB. Additionally, we found weaker functional connectivity in the AMB group from right to left auditory cortex, despite their stronger neural responses overall.

CONCLUSION

Our results reveal abnormally large auditory sensory encoding and an imbalance in communication between cerebral hemispheres (ipsi- to -contralateral signaling) in AMB.

SIGNIFICANCE

These neurophysiological changes might lead to the functionally poorer behavioral capacity to integrate information between the two ears in children with AMB.

Early Sensory Deprivation Leads to Differential Inhibitory Changes in the Striatum During Learning

The corticostriatal circuit has been identified as a vital pathway for associative learning. However, how learning is implemented when the sensory striatum is permanently impaired remains unclear. Using chemogenetic techniques to suppress layer five auditory cortex (AC) input to the auditory striatum, learning of a sound discrimination task was significantly impacted in freely moving Mongolian gerbils, in particular when this suppression occurs early on during learning. Whole-cell recordings sampled throughout learning revealed a transient reduction in postsynaptic (GABAA) inhibition in both striatal D1 and D2 cells in normal-hearing gerbils during task acquisition. In contrast, when the baseline striatal inhibitory strengths and firing rates were permanently reduced by a transient period of developmental sensory deprivation, learning was accompanied by augmented inhibition and increased firing rates. Direct manipulation of striatal inhibition in vivo and in vitro revealed a key role of the transient inhibitory changes in task acquisition. Together, these results reveal a flexible corticostriatal inhibitory synaptic plasticity mechanism that accompanies associative auditory learning.

Central auditory processing in teenagers with non-cholesteatomatous chronic otitis media

Introduction

Evidences of possible effects of early age otitis media with effusion in the central auditory processing, emphasize the need to consider such effects also in subjects with chronic otitis media.

Aim

To investigate and analyze the impact of non-cholesteatomatous chronic otitis media on central auditory processing in teenagers.

Methods

This is a study in which 68 teenagers were recruited, 34 with a diagnosis of non-cholesteatomatous chronic otitis media (study group) and 34 without otological disease history (control group). The evaluation of the subjects consisted of: anamnesis, pure-tone threshold audiometry, speech audiometry and a behavioral test battery for assessment of central auditory processing.

Results

A statistically significant difference was found between the means observed in the study and control groups in all tests performed. An association was found between the control group and subgroups of the study group with unilateral alterations in all tests. An association was shown between the results for the control group and study group for family income, with a greater impact on subjects with a lower income.

Conclusions

Non-cholesteatomatous chronic otitis media affects the central auditory processing in teenagers suffering from the disorder, and monaural low-redundancy hearing is the most affected auditory mechanism. Unilateral conductive changes cause more damage than bilateral ones, and lower family income seems to lead to more changes to the central auditory processing of subjects with non-cholesteatomatous chronic otitis media.

The effects of otitis media with effusion on the measurement of auditory evoked potentials

OBJECTIVE

The aim of this study was to explore the impact of otitis media on auditory evoked potentials in children with a history of otitis media in comparison to a control group.

DESIGN

90 children, with normal hearing and middle ear status at time of assessment, aged between 8 and 14 years (44 boys and 46 girls) were enrolled in this study. 50 children (28 boys and 22 girls) had a documented history of Otitis Media. The control group consisted of 40 children (17 boys and 23 girls) with no documented history of otitis media. All children completed the auditory evoked potentials tasks of Auditory Brainstem Response (ABR) and P300.

RESULTS

Auditory Evoked Potentials results demonstrated significantly increased latencies and decreased amplitudes in the otitis media group. ABR showed significantly latency delay of waves III and V by 0.1 msec (p < 0.001) and reduced amplitude (0.06 μV, p = 0.002 and 0.05 μV, p = 0.008, respectively) in the otitis media group compared to control group. P300 also showed significant latency delays (13,41 ms, p = 0.008) in otitis media group. No significant difference was seen for amplitude between CG and otitis media group for P300.

CONCLUSION

The results demonstrate the negative effects of otitis media on auditory evoked potentials in children with a history of middle ear disease as can be seen by changes on the ABR and P300 measures.

Extended high-frequency hearing enhances speech perception in noise

Young healthy adults can hear tones up to at least 20 kHz. However, clinical audiometry, by which hearing loss is diagnosed, is limited at high frequencies to 8 kHz. Evidence suggests there is salient information at extended high frequencies (EHFs; 8 to 20 kHz) that may influence speech intelligibility, but whether that information is used in challenging listening conditions remains unknown. Difficulty understanding speech in noisy environments is the most common concern people have about their hearing and usually the first sign of age-related hearing loss. Digits-in-noise (DIN), a widely used test of speech-in-noise perception, can be sensitized for detection of high-frequency hearing loss by low-pass filtering the broadband masking noise. Here, we used standard and EHF audiometry, self-report, and successively higher cutoff frequency filters (2 to 8 kHz) in a DIN test to investigate contributions of higher-frequency hearing to speech-in-noise perception. Three surprising results were found. First, 74 of 116 "normally hearing," mostly younger adults had some hearing loss at frequencies above 8 kHz. Early EHF hearing loss may thus be an easily measured, preventive warning to protect hearing. Second, EHF hearing loss correlated with self-reported difficulty hearing in noise. Finally, even with the broadest filtered noise (≤8 kHz), DIN hearing thresholds were significantly better (P < 0.0001) than those using broadband noise. Sound energy above 8 kHz thus contributes to speech perception in noise. People with "normal hearing" frequently report difficulty hearing in challenging environments. Our results suggest that one contribution to this difficulty is EHF hearing loss.

Preserving Inhibition during Developmental Hearing Loss Rescues Auditory Learning and Perception

Transient periods of childhood hearing loss can induce deficits in aural communication that persist long after auditory thresholds have returned to normal, reflecting long-lasting impairments to the auditory CNS. Here, we asked whether these behavioral deficits could be reversed by treating one of the central impairments: reduction of inhibitory strength. Male and female gerbils received bilateral earplugs to induce a mild, reversible hearing loss during the critical period of auditory cortex development. After earplug removal and the return of normal auditory thresholds, we trained and tested animals on an amplitude modulation detection task. Transient developmental hearing loss induced both learning and perceptual deficits, which were entirely corrected by treatment with a selective GABA reuptake inhibitor (SGRI). To explore the mechanistic basis for these behavioral findings, we recorded the amplitudes of GABA_A and GABA_B receptor-mediated IPSPs in auditory cortical and thalamic brain slices. In hearing loss-reared animals, cortical IPSP amplitudes were significantly reduced within a few days of hearing loss onset, and this reduction persisted into adulthood. SGRI treatment during the critical period prevented the hearing loss-induced reduction of IPSP amplitudes; but when administered after the critical period, it only restored GABA_B receptor-mediated IPSP amplitudes. These effects were driven, in part, by the ability of SGRI to upregulate α1 subunit-dependent GABA_A responses. Similarly, SGRI prevented the hearing loss-induced reduction of GABA_A and GABA_B IPSPs in the ventral nucleus of the medial geniculate body. Thus, by maintaining, or subsequently rescuing, GABAergic transmission in the central auditory thalamocortical pathway, some perceptual and cognitive deficits induced by developmental hearing loss can be prevented.SIGNIFICANCE STATEMENT Even a temporary period of childhood hearing loss can induce communication deficits that persist long after auditory thresholds return to normal. These deficits may arise from long-lasting central impairments, including the loss of synaptic inhibition. Here, we asked whether hearing loss-induced behavioral deficits could be reversed by reinstating normal inhibitory strength. Gerbils reared with transient hearing loss displayed both learning and perceptual deficits. However, when animals were treated with a selective GABA reuptake inhibitor during or after hearing loss, behavioral deficits were entirely corrected. This behavioral recovery was correlated with the return of normal thalamic and cortical inhibitory function. Thus, some perceptual and cognitive deficits induced by developmental hearing loss were prevented with a treatment that rescues a central synaptic property.

Amplitude Modulation Detection in Children with a History of Temporary Conductive Hearing Loss Remains Impaired for Years After Restoration of Normal Hearing

Otitis media with effusion (OME) is considered a form of relative sensory deprivation that often occurs during a critical period of language acquisition in children. Animal studies have demonstrated that hearing loss during early development can impair behavioral sensitivity to amplitude modulation (AM), critical for speech understanding, even after restoration of normal hearing thresholds. AM detection in humans with a history of OME-associated conductive hearing loss (CHL) has not been previously investigated. Our objective was to determine whether OME-associated CHL in children ages 6 months to 3 years results in deficits in AM detection in later childhood, after restoration of normal audiometric thresholds. Children ages 4 to 7 years with and without a history of OME-associated CHL participated in an AM detection two-alternative forced-choice task at 8 and 64 Hz modulation frequencies using a noise carrier signal and an interactive touch screen interface. Thirty-four subjects were studied (17 with a history of OME-related CHL and 17 without). Modulation detection thresholds improved with age and were slightly lower (more sensitive) for the 64 Hz modulation frequency for both groups. Modulation detection thresholds of children with a history of OME-associated CHL were higher than control thresholds at 5 years, but corrected to expected levels between ages 6-7. OME-associated CHL results in impaired AM detection, even when measured years after restoration of normal audiometric thresholds. Future studies may shed light on implications for speech and language development and academic success for children affected by OME and associated conductive hearing loss.

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.

Precision-scored parental report questions and HL-scaled tympanometry as informative measures of hearing in otitis media 1: Large-sample evidence on determinants and complementarity to pure-tone audiometry

INTRODUCTION

In otitis media with effusion (OME), hearing loss is a core sign/symptom and basis of concern, with absolute pure-tone threshold sensitivity (in dB HL) by air-conduction providing the default measure of hearing. However several fundamental problems limiting the value of HL measures in otitis media are insufficiently appreciated. To appraise the joint value and implications of multiple hearing measures towards more comprehensive hearing assessment in OM, we examine in two related articles the interrelations and common or diverging determinants of three measures, two of them objective: binaural HL, and ACET (the published quasi-continuous scaling of binaural tympanometry to HL). The third measure is partly subjective: parentally reported hearing difficulties (RHD-4); this is the precision-scored total of the 4 items selected for the OM8-30 general purpose questionnaire for parents in OM.

METHODS

The Eurotitis-2 study (Total N=2886) internationally standardises OM8-30 and its OMQ-14 short form. The clinical and parent-response variables acquired cover many issues in diagnosis, symptomatology and impact of OM. Data acquisition was built upon routine clinic practice, enabling us also to document some properties of that practice, such as patterns of missing HL data. To address possible confounding or loss of representativeness from this, we investigated the implications of substituting tympanometry-based ACET for missing HL to give an HL/ACET hybrid. ACET is the mapping of categorical tympanometry to continuous HL. We simulated degrees of artificial missingness of HL up to 35% on the 1430 complete-data cases, using random deletion, with 1000-version bootstrapping. Correlations of this HL/ACET hybrid with pure (100%) HL then documented the degree of correlation retained under dilution of HL by an admixture of ACET; we also documented distribution shapes. For RHD-4, we then probed the determining influences on severity of score as an auditory disability measure, both background ones (from centre, age, sex, socio-economic status, length of history, diagnosis and season) and the two underlying objective hearing measures (HL, ACET). We ran these multiple regressions (GLMs), for representativeness and generality, both on 1430 complete-data cases (i.e. all 3 hearing variables present) and also on supplemented samples according to data required only for particular analyses (N increased by +56% to +68%). A further method of sample supplementation (by up to +96%) used the HL/ACET hybrid.

RESULTS

Sex made negligible difference in any analysis. The particular collaborating centre, age, season and diagnosis collectively influenced presence/absence of HL data very strongly. (Area under ROC 0.944). Socio-economic status did not influence HL presence; surprisingly, nor did RHD, ACET or length of history, after control for centre, age, diagnosis and season. Of the inter-correlations between hearing measures, only the one between ACET and RHD was influenced (slightly reduced) by the inclusion of cases without HL data. In the simulated substitutions, Pearson correlation of hybrid HL/ACET with true HL remained above 0.90 for substitution by ACET of up to 30% rate of artificially 'missing' HL. Centre differences were adequately summarised by simple absolute additive differences in mean local case severity. In the determinant models for RHD on the 1430 complete-data cases, HL and the set of background determinants collectively explained broadly similar proportions of RHD's variability, totalling 36.8% explained. On the larger maximum case samples, slightly less absolute variability was explicable than on complete-case data, but relative magnitudes of contribution from individual determinants, both background and hearing measures, remained similar. The expected mean differences in RHD between diagnoses (RAOM, OME, and combined) were found, but the patterns of background and objective measure influences determining RHD did not differ significantly between the diagnoses.

CONCLUSIONS

(1) In the Eurotitis-2 database, descriptive differences in various background demographic and clinical measures between cases on whom HL data were obtained versus not, were only of material magnitude for length of history and reported hearing difficulties. Such descriptive differences are not necessarily bases of confounding, so using our framework of 6 background adjuster variables, (particular collaborating centre, age, season, diagnosis, socioeconomic status and length of history) we isolated the determinants of HL data presence. The first four listed strongly predicted HL data presence/absence so are sufficient to control analyses well for any bias or confounding by HL data presence. (2) Diagnoses as OME and combined (OME+RAOM) had higher probability of HL data being present relative to RAOM, indicating that HL acquisition is chiefly seen as confirming and quantifying hearing loss in (suspect) OME, not as ruling it out (e.g. in suspected RAOM). Given this, also using RHD and or ACET as pre-triage to efficiently target capacity and/or reduce costs and opportunity costs of acquiring HL would be rational, but there was no evidence of such precise use of initial hearing-related information to decide on HL acquisition. (3) The full six background variables explained comparable variance in Reported Hearing Difficulties (RHD) to what was explained by ACET, but not quite as much as by HL. Achieving a high percentage explained (32-37% from good models) required both classes of determinant to be entered as predictors. The pattern of background determining influences for RHD was largely stable, with or without objective measures as additional predictors, and on maximum or complete-data cases. Length of history strongly determines RHD for a given concurrent HL. (4) Accepting ACET as substitute where HL was missing in OM cases gave a sample-size enhancement of 17% in Eurotitis-2, with negligible difference in the pattern of determinants. This hybrid measure can be recommended as reasonable next-best when moderate percentages of HL data are missing. (5) The stable pattern of prediction of RHD suggests that our six background determinants provide a very promising low-cost yet comprehensive framework for determination. It hence offers pluripotent statistical adjustment against confounding, applicable to RAOM, OME and combined diagnoses in any analysis using this database. Claims that it thereby offers a sufficient framework for full European standardisation of all the scores from the OM8-30 questionnaire measures await parallel demonstrations for symptom areas other than RHD. As 25% of the variance in RHD severity can be explained by the six adjusters in our framework, none of the six variables should be omitted from acquisition and analytic use in future OM research.

Amblyaudia: Review of Pathophysiology, Clinical Presentation, and Treatment of a New Diagnosis

OBJECTIVE

Similar to amblyopia in the visual system, "amblyaudia" is a term used to describe persistent hearing difficulty experienced by individuals with a history of asymmetric hearing loss (AHL) during a critical window of brain development. Few clinical reports have described this phenomenon and its consequent effects on central auditory processing. We aim to (1) define the concept of amblyaudia and (2) review contemporary research on its pathophysiology and emerging clinical relevance.

DATA SOURCES

PubMed, Embase, and Cochrane databases.

REVIEW METHODS

A systematic literature search was performed with combinations of search terms: "amblyaudia," "conductive hearing loss," "sensorineural hearing loss," "asymmetric," "pediatric," "auditory deprivation," and "auditory development." Relevant articles were considered for inclusion, including basic and clinical studies, case series, and major reviews.

CONCLUSIONS

During critical periods of infant brain development, imbalanced auditory input associated with AHL may lead to abnormalities in binaural processing. Patients with amblyaudia can demonstrate long-term deficits in auditory perception even with correction or resolution of AHL. The greatest impact is in sound localization and hearing in noisy environments, both of which rely on bilateral auditory cues. Diagnosis and quantification of amblyaudia remain controversial and poorly defined. Prevention of amblyaudia may be possible through early identification and timely management of reversible causes of AHL.

IMPLICATIONS FOR PRACTICE

Otolaryngologists, audiologists, and pediatricians should be aware of emerging data supporting amblyaudia as a diagnostic entity and be cognizant of the potential for lasting consequences of AHL. Prevention of long-term auditory deficits may be possible through rapid identification and correction.

Sustained Perceptual Deficits from Transient Sensory Deprivation

Sensory pathways display heightened plasticity during development, yet the perceptual consequences of early experience are generally assessed in adulthood. This approach does not allow one to identify transient perceptual changes that may be linked to the central plasticity observed in juvenile animals. Here, we determined whether a brief period of bilateral auditory deprivation affects sound perception in developing and adult gerbils. Animals were reared with bilateral earplugs, either from postnatal day 11 (P11) to postnatal day 23 (P23) (a manipulation previously found to disrupt gerbil cortical properties), or from P23-P35. Fifteen days after earplug removal and restoration of normal thresholds, animals were tested on their ability to detect the presence of amplitude modulation (AM), a temporal cue that supports vocal communication. Animals reared with earplugs from P11-P23 displayed elevated AM detection thresholds, compared with age-matched controls. In contrast, an identical period of earplug rearing at a later age (P23-P35) did not impair auditory perception. Although the AM thresholds of earplug-reared juveniles improved during a week of repeated testing, a subset of juveniles continued to display a perceptual deficit. Furthermore, although the perceptual deficits induced by transient earplug rearing had resolved for most animals by adulthood, a subset of adults displayed impaired performance. Control experiments indicated that earplugging did not disrupt the integrity of the auditory periphery. Together, our results suggest that P11-P23 encompasses a critical period during which sensory deprivation disrupts central mechanisms that support auditory perceptual skills.

SIGNIFICANCE STATEMENT

Sensory systems are particularly malleable during development. This heightened degree of plasticity is beneficial because it enables the acquisition of complex skills, such as music or language. However, this plasticity comes with a cost: nervous system development displays an increased vulnerability to the sensory environment. Here, we identify a precise developmental window during which mild hearing loss affects the maturation of an auditory perceptual cue that is known to support animal communication, including human speech. Furthermore, animals reared with transient hearing loss display deficits in perceptual learning. Our results suggest that speech and language delays associated with transient or permanent childhood hearing loss may be accounted for, in part, by deficits in central auditory processing mechanisms.

Auditory temporal abilities in children with history of recurrent otitis media in the first years of life and persistent in preschool and school ages

PURPOSE

To study the temporal auditory ordering and resolution abilities in children with and without a history of early OME and ROME, as well as to study the responses according to age.

METHODS

A total of 59 children were evaluated, and all of them presented pure tone thresholds within the normal range at the time of the conduction of the hearing tests. The children were divided into two groups according to the occurrence of episodes of recurrent otitis media. Then, each group was divided into two subgroups according to age: 7- and 8-year olds, and 9- and 10-year olds. All children were assessed with standard tests of temporal frequency (ordination) and gaps-in-noise (resolution).

RESULTS

For the temporal abilities studied, children with a history of otitis media presented significantly lower results compared to the control group. In the frequency pattern test, the correct answers increased with age in both groups. In the identification of silence intervals, the control group showed no change in threshold regarding to age, but this change was present in the group with a history of otitis media.

CONCLUSION

Episodes of otitis media with effusion in the first year of life, recurrent and persistent in preschool and school ages, negatively influence the temporal ordering and resolution abilities.

Sources of pathology underlying listening disorders in children

Some children referred to audiology and developmental disability services have listening difficulties, despite normal audiograms. These children may be tested for 'auditory processing disorder' (APD), a controversial construct suggesting that neural dysfunction in the central auditory system leads to impaired auditory perception. An important question, not currently tested in clinical evaluation, is whether listening difficulties result from problems with bottom-up auditory sensory processing or top-down modulating cognition. Perceptual variability and poor performance on standardized tests suggest that listening difficulties are primarily cognitive in origin. However, evidence for impaired olivocochlear function and temporal processing deficits may implicate peripheral or central auditory dysfunction in some cases. Wide-spread, top-down modulation of auditory cortical, brainstem and ear function suggests that afferent and efferent control systems may not be simple to segregate. During normal maturation, hearing appears to develop in proportion to the complexity of both stimuli and tasks. But some younger individuals have mature hearing, highlighting individual differences that suggest APD may be due to a generalized developmental delay. Recent studies have investigated specific hypotheses showing, for example, that spatial hearing and executive function are compromised in some children with listening difficulties. Using speech stimuli (e.g. consonant-vowel syllables) to examine auditory brainstem responses, and psychophysiological relations between dichotic hearing and cortical physiology, various effects of auditory experience and development point the way to promising approaches for further studies of APD. Newer technology, from genetic sequencing to MRI, may have the sensitivity to test whether and how frequently APD is associated with impaired processing in the auditory system.

Transient Hearing Loss Within a Critical Period Causes Persistent Changes to Cellular Properties in Adult Auditory Cortex

Sensory deprivation can induce profound changes to central processing during developmental critical periods (CPs), and the recovery of normal function is maximal if the sensory input is restored during these epochs. Therefore, we asked whether mild and transient hearing loss (HL) during discrete CPs could induce changes to cortical cellular physiology. Electrical and inhibitory synaptic properties were obtained from auditory cortex pyramidal neurons using whole-cell recordings after bilateral earplug insertion or following earplug removal. Varying the age of HL onset revealed brief CPs of vulnerability for membrane and firing properties, as well as, inhibitory synaptic currents. These CPs closed 1 week after ear canal opening on postnatal day (P) 18. To examine whether the cellular properties could recover from HL, earplugs were removed prior to (P17) or after (P23), the closure of these CPs. The earlier age of hearing restoration led to greater recovery of cellular function, but firing rate remained disrupted. When earplugs were removed after the closure of these CPs, several changes persisted into adulthood. Therefore, long-lasting cellular deficits that emerge from transient deprivation during a CP may contribute to delayed acquisition of auditory skills in children who experience temporary HL.

Glue ear, hearing loss and IQ: an association moderated by the child's home environment

BACKGROUND

Glue ear or otitis media with effusion (OME) is common in children and may be associated with hearing loss (HL). For most children it has no long lasting effects on cognitive development but it is unclear whether there are subgroups at higher risk of sequelae.

OBJECTIVES

To examine the association between a score comprising the number of times a child had OME and HL (OME/HL score) in the first four/five years of life and IQ at age 4 and 8. To examine whether any association between OME/HL and IQ is moderated by socioeconomic, child or family factors.

METHODS

Prospective, longitudinal cohort study: the Avon Longitudinal Study of Parents and Children (ALSPAC). 1155 children tested using tympanometry on up to nine occasions and hearing for speech (word recognition) on up to three occasions between age 8 months and 5 years. An OME/HL score was created and associations with IQ at ages 4 and 8 were examined. Potential moderators included a measure of the child's cognitive stimulation at home (HOME score).

RESULTS

For the whole sample at age 4 the group with the highest 10% OME/HL scores had performance IQ 5 points lower [95% CI -9, -1] and verbal IQ 6 points lower [95% CI -10, -3] than the unaffected group. By age 8 the evidence for group differences was weak. There were significant interactions between OME/HL and the HOME score: those with high OME/HL scores and low 18 month HOME scores had lower IQ at age 4 and 8 than those with high OME/HL scores and high HOME scores. Adjusted mean differences ranged from 5 to 8 IQ points at age 4 and 8.

CONCLUSIONS

The cognitive development of children from homes with lower levels of cognitive stimulation is susceptible to the effects of glue ear and hearing loss.

Developmental plasticity of spatial hearing following asymmetric hearing loss: context-dependent cue integration and its clinical implications

Under normal hearing conditions, comparisons of the sounds reaching each ear are critical for accurate sound localization. Asymmetric hearing loss should therefore degrade spatial hearing and has become an important experimental tool for probing the plasticity of the auditory system, both during development and adulthood. In clinical populations, hearing loss affecting one ear more than the other is commonly associated with otitis media with effusion, a disorder experienced by approximately 80% of children before the age of two. Asymmetric hearing may also arise in other clinical situations, such as after unilateral cochlear implantation. Here, we consider the role played by spatial cue integration in sound localization under normal acoustical conditions. We then review evidence for adaptive changes in spatial hearing following a developmental hearing loss in one ear, and show that adaptation may be achieved either by learning a new relationship between the altered cues and directions in space or by changing the way different cues are integrated in the brain. We next consider developmental plasticity as a source of vulnerability, describing maladaptive effects of asymmetric hearing loss that persist even when normal hearing is provided. We also examine the extent to which the consequences of asymmetric hearing loss depend upon its timing and duration. Although much of the experimental literature has focused on the effects of a stable unilateral hearing loss, some of the most common hearing impairments experienced by children tend to fluctuate over time. We therefore propose that there is a need to bridge this gap by investigating the effects of recurring hearing loss during development, and outline recent steps in this direction. We conclude by arguing that this work points toward a more nuanced view of developmental plasticity, in which plasticity may be selectively expressed in response to specific sensory contexts, and consider the clinical implications of this.

Conductive hearing loss induced by experimental middle-ear effusion in a chinchilla model reveals impaired tympanic membrane-coupled ossicular chain movement

Otitis media with effusion (OME) occurs when fluid collects in the middle-ear space behind the tympanic membrane (TM). As a result of this effusion, sounds can become attenuated by as much as 30-40 dB, causing a conductive hearing loss (CHL). However, the exact mechanical cause of the hearing loss remains unclear. Possible causes can include altered compliance of the TM, inefficient movement of the ossicular chain, decreased compliance of the oval window-stapes footplate complex, or altered input to the oval and round window due to conduction of sound energy through middle-ear fluid. Here, we studied the contribution of TM motion and umbo velocity to a CHL caused by middle-ear effusion. Using the chinchilla as an animal model, umbo velocity (V U) and cochlear microphonic (CM) responses were measured simultaneously using sinusoidal tone pip stimuli (125 Hz-12 kHz) before and after filling the middle ear with different volumes (0.5-2.0 mL) of silicone oil (viscosity, 3.5 Poise). Concurrent increases in CM thresholds and decreases in umbo velocity were noted after the middle ear was filled with 1.0 mL or more of fluid. Across animals, completely filling the middle ear with fluid caused 20-40-dB increases in CM thresholds and 15-35-dB attenuations in umbo velocity. Clinic-standard 226-Hz tympanometry was insensitive to fluid-associated changes in CM thresholds until virtually the entire middle-ear cavity had been filled (approximately >1.5 mL). The changes in umbo velocity, CM thresholds, and tympanometry due to experimentally induced OME suggest CHL arises primarily as a result of impaired TM mobility and TM-coupled umbo motion plus additional mechanisms within the middle ear.

Hearing and otitis media with effusion in young adults with cleft lip and palate

CONCLUSION

Speech recognition in noise is affected when otitis media with effusion (OME) is present in young adults with unilateral cleft lip and palate.

OBJECTIVE

The objective of this study was to describe the hearing and performance on auditory tasks of young adults with unilateral cleft lip and palate as compared to young adults without cleft lip and palate.

METHODS

Twenty-six young adults with unilateral cleft lip and palate and 23 young adults without cleft lip and palate participated in the study. Pure tone audiometry, tympanometry, speech recognition in noise at the word and sentence level, and masking level difference were examined.

RESULTS

Results revealed elevated hearing thresholds in the young adults with cleft lip and palate as compared with young adults without cleft lip and palate. No differences concerning speech recognition in noise and binaural processing were observed between the young adults with cleft lip and palate and those without. However, there was poorer speech recognition performance in those adults with unilateral cleft lip and palate and OME on the day of testing as compared with young adults with unilateral cleft lip and palate without OME on the day of testing.

The conductive hearing loss due to an experimentally induced middle ear effusion alters the interaural level and time difference cues to sound location

Otitis media with effusion (OME) is a pathologic condition of the middle ear that leads to a mild to moderate conductive hearing loss as a result of fluid in the middle ear. Recurring OME in children during the first few years of life has been shown to be associated with poor detection and recognition of sounds in noisy environments, hypothesized to result due to altered sound localization cues. To explore this hypothesis, we simulated a middle ear effusion by filling the middle ear space of chinchillas with different viscosities and volumes of silicone oil to simulate varying degrees of OME. While the effects of middle ear effusions on the interaural level difference (ILD) cue to location are known, little is known about whether and how middle ear effusions affect interaural time differences (ITDs). Cochlear microphonic amplitudes and phases were measured in response to sounds delivered from several locations in azimuth before and after filling the middle ear with fluid. Significant attenuations (20-40 dB) of sound were observed when the middle ear was filled with at least 1.0 ml of fluid with a viscosity of 3.5 Poise (P) or greater. As expected, ILDs were altered by ~30 dB. Additionally, ITDs were shifted by ~600 μs for low frequency stimuli (<4 kHz) due to a delay in the transmission of sound to the inner ear. The data show that in an experimental model of OME, ILDs and ITDs are shifted in the spatial direction of the ear without the experimental effusion.

Stroke recovery and sensory plasticity: common mechanisms?

Presentations in this symposium are considered in the context of mechanisms of sensory plasticity, particularly in the auditory system. The auditory nervous system has two discrete end organs that are separately vulnerable to clinical and experimental injury, and brainstem processing mechanisms that are highly specialized for temporal, spectral, and spatial coding. These include giant axo-somatic synapses and neurons with spatially segregated bipolar dendrites, each innervated exclusively from one ear. This architecture allows exquisite control of afferent-target interactions, including known excitatory and inhibitory couplings, and consequently enhanced interpretation of data from other brain systems. For example, deafening can silence the auditory nerve, but has surprisingly little impact on normal brain function, as evidenced by the success of cochlear implants. The observed amplification from one brain region to another of degeneration following stroke or discrete brain lesions may thus be due to secondary rather than primary afferent consequences of the lesion.

Auditory processing in children and adolescents in situations of risk and vulnerability

CONTEXT AND OBJECTIVE

Children and adolescents who live in situations of social vulnerability present a series of health problems. Nonetheless, affirmations that sensory and cognitive abnormalities are present are a matter of controversy. The aim of this study was to investigate aspects to auditory processing, through applying the brainstem auditory evoked potential (BAEP) and behavioral auditory processing tests to children living on the streets, and comparison with a control group.

DESIGN AND SETTING

Cross-sectional study in the Laboratory of Auditory Processing, School of Medicine, Universidade de São Paulo.

METHODS

The auditory processing tests were applied to a group of 27 individuals, subdivided into 11 children (7 to 10 years old) and 16 adolescents (11 to 16 years old), of both sexes, in situations of social vulnerability, compared with an age-matched control group of 10 children and 11 adolescents without complaints. The BAEP test was also applied to investigate the integrity of the auditory pathway.

RESULTS

For both children and adolescents, there were significant differences between the study and control groups in most of the tests applied, with significantly worse performance in the study group, except in the pediatric speech intelligibility test. Only one child had an abnormal result in the BAEP test.

CONCLUSIONS

The results showed that the study group (children and adolescents) presented poor performance in the behavioral auditory processing tests, despite their unaltered auditory brainstem pathways, as shown by their normal results in the BAEP test.

Evaluating the perceptual and pathophysiological consequences of auditory deprivation in early postnatal life: a comparison of basic and clinical studies

Decades of clinical and basic research in visual system development have shown that degraded or imbalanced visual inputs can induce a long-lasting visual impairment called amblyopia. In the auditory domain, it is well established that inducing a conductive hearing loss (CHL) in young laboratory animals is associated with a panoply of central auditory system irregularities, ranging from cellular morphology to behavior. Human auditory deprivation, in the form of otitis media (OM), is tremendously common in young children, yet the evidence linking a history of OM to long-lasting auditory processing impairments has been equivocal for decades. Here, we review the apparent discrepancies in the clinical and basic auditory literature and provide a meta-analysis to show that the evidence for human amblyaudia, the auditory analog of amblyopia, is considerably more compelling than is generally believed. We argue that a major cause for this discrepancy is the fact that most clinical studies attempt to link central auditory deficits to a history of middle ear pathology, when the primary risk factor for brain-based developmental impairments such as amblyopia and amblyaudia is whether the afferent sensory signal is degraded during critical periods of brain development. Accordingly, clinical studies that target the subset of children with a history of OM that is also accompanied by elevated hearing thresholds consistently identify perceptual and physiological deficits that can endure for years after peripheral hearing is audiometrically normal, in keeping with the animal studies on CHL. These studies suggest that infants with OM severe enough to cause degraded afferent signal transmission (e.g., CHL) are particularly at risk to develop lasting central auditory impairments. We propose some practical guidelines to identify at-risk infants and test for the positive expression of amblyaudia in older children.

Spatial hearing of normally hearing and cochlear implanted children

OBJECTIVE

Spatial hearing uses both monaural and binaural mechanisms that require sensitive hearing for normal function. Deaf children using either bilateral (BCI) or unilateral (UCI) cochlear implants would thus be expected to have poorer spatial hearing than normally hearing (NH) children. However, the relationship between spatial hearing in these various listener groups has not previously been extensively tested under ecologically valid conditions using a homogeneous group of children who are UCI users. We predicted that NH listeners would outperform BCI listeners who would, in turn, outperform UCI listeners.

METHODS

We tested two methods of spatial hearing to provide norms for NH and UCI using children and preliminary data for BCI users. NH children (n=40) were age matched (6-15 years) to UCI (n=12) and BCI (n=6) listeners. Testing used a horizontal ring of loudspeakers within a booth in a hospital outpatient clinic. In a 'lateral release' task, single nouns were presented frontally, and masking noises were presented frontally, or 90° left or right. In a 'localization' task, allowing head movements, nouns were presented from loudspeakers separated by 30°, 60° or 120° about the midline.

RESULTS

Normally hearing children improved with age in speech detection in noise, but not in quiet or in lateral release. Implant users performed more poorly on all tasks. For frontal signals and noise, UCI and BCI listeners did not differ. For lateral noise, BCI listeners performed better on both sides (within ~2 dB of NH), whereas UCI listeners benefited only when the noise was opposite the unimplanted ear. Both the BCI and, surprisingly, the UCI listeners performed better than chance at all loudspeaker separations on the ecologically valid, localization task. However, the BCI listeners performed about twice as well and, in two cases, approached the performance of NH children.

CONCLUSION

Children using either UCI or BCI have useful spatial hearing. BCI listeners gain benefits on both sides, and localize better, but not as well as NH listeners.

Communication, listening, cognitive and speech perception skills in children with auditory processing disorder (APD) or Specific Language Impairment (SLI)

PURPOSE

Parental reports of communication, listening, and behavior in children receiving a clinical diagnosis of specific language impairment (SLI) or auditory processing disorder (APD) were compared with direct tests of intelligence, memory, language, phonology, literacy, and speech intelligibility. The primary aim was to identify whether there were differences between these characteristics in children with SLI or APD.

METHOD

Normally hearing children who were clinically diagnosed with SLI (n = 22) or APD (n = 19), and a quasirandom sample of mainstream school (MS) children (n = 47) aged 6-13 years, underwent tests of verbal and nonverbal IQ, digit span, nonsense word repetition, Spoonerisms, reading, grammar, and sentence and VCV nonword intelligibility. Parents completed questionnaires on the children's communication, listening, and behavior.

RESULTS

There was generally no difference between the performance of the children with SLI and the children with APD on the questionnaire and test measures, and both groups consistently and significantly underperformed compared with the children in the MS group. Speech intelligibility in both noise and quiet was unimpaired in the SLI and APD groups.

CONCLUSION

Despite clinical diagnoses of SLI or APD, the 2 groups of children had very similar behavioral and parental report profiles, suggesting that the children were differentially diagnosed based on their referral route rather than on actual differences.

The effects of experimentally induced conductive hearing loss on spectral and temporal aspects of sound transmission through the ear

Conductive hearing loss (CHL) is known to produce hearing deficits, including deficits in sound localization ability. The differences in sound intensities and timing experienced between the two tympanic membranes are important cues to sound localization (ILD and ITD, respectively). Although much is known about the effect of CHL on hearing levels, little investigation has been conducted into the actual impact of CHL on sound location cues. This study investigated effects of CHL induced by earplugs on cochlear microphonic (CM) amplitude and timing and their corresponding effect on the ILD and ITD location cues. Acoustic and CM measurements were made in 5 chinchillas before and after earplug insertion, and again after earplug removal using pure tones (500 Hz to 24 kHz). ILDs in the unoccluded condition demonstrated position and frequency dependence where peak far-lateral ILDs approached 30 dB for high frequencies. Unoccluded ear ITD cues demonstrated positional and frequency dependence with increased ITD cue for both decreasing frequency (±420 μs at 500 Hz, ±310 μs for 1-4 kHz) and increasingly lateral sound source locations. Occlusion of the ear canal with foam plugs resulted in a mild, frequency-dependent conductive hearing loss of 10-38 dB (mean 31 ± 3.9 dB) leading to a concomitant frequency dependent increase in ILDs at all source locations. The effective ITDs increased in a frequency dependent manner with ear occlusion as a direct result of the acoustic properties of the plugging material, the latter confirmed via acoustical measurements using a model ear canal with varying volumes of acoustic foam. Upon ear plugging with acoustic foam, a mild CHL is induced. Furthermore, the CHL induced by acoustic foam results in substantial changes in the magnitudes of both the ITD and ILD cues to sound location.

Monaural deprivation disrupts development of binaural selectivity in auditory midbrain and cortex

Degraded sensory experience during critical periods of development can have adverse effects on brain function. In the auditory system, conductive hearing loss associated with childhood ear infections can produce long-lasting deficits in auditory perceptual acuity, much like amblyopia in the visual system. Here we explore the neural mechanisms that may underlie "amblyaudio" by inducing reversible monaural deprivation (MD) in infant, juvenile, and adult rats. MD distorted tonotopic maps, weakened the deprived ear's representation, strengthened the open ear's representation, and disrupted binaural integration of interaural level differences (ILD). Bidirectional plasticity effects were strictly governed by critical periods, were more strongly expressed in primary auditory cortex than inferior colliculus, and directly impacted neural coding accuracy. These findings highlight a remarkable degree of competitive plasticity between aural representations and suggest that the enduring perceptual sequelae of childhood hearing loss might be traced to maladaptive plasticity during critical periods of auditory cortex development.

Developmental hearing loss disrupts synaptic inhibition: implications for auditory processing

Hearing loss during development leads to central deficits that persist even after the restoration of peripheral function. One key class of deficits is due to changes in central inhibitory synapses, which play a fundamental role in all aspects of auditory processing. This review focuses on the anatomical and physiological alterations of inhibitory connections at several regions within the central auditory pathway following hearing loss. Such aberrant inhibitory synaptic function may be linked to deficits in encoding binaural and spectral cues. Understanding the cellular changes that occur at inhibitory synapses following hearing loss may provide specific loci that can be targeted to improve function.

Prevalence of OME Is Reduced in Young Children Using Chewing Gum

OBJECTIVE

The present study investigates a possible relationship between use of chewing gum and otitis media with effusion (OME) in children. Chewing obviously activates jaw movements, increases salivary flow, and, by the way, the rate of swallowing and the rate of activations of peritubal muscles and tubal openings. Chewing also requires nasal respiration, thus preventing mouth breathing.

DESIGN

Cross-sectional study: 1756 children (2 to 6 yr of age), apparently in good health and visiting different Dutch child health centers in the region of Utrecht were examined between September 1999 and April 2002. OME was diagnosed by combined tympanometry and otoscopy. The criterion for OME was unilateral or bilateral type B tympanogram, according to Jerger. The parents had to fill out a questionnaire with a question pertaining to the chewing habits of their child.

RESULTS

Logistic regression points out that age and season as well as chewing gum-consuming habits significantly influence the prevalence of OME. The strongest effects are age (OME becomes less frequent with age) and season (OME occurs less when climate is more favorable), but -- ceteris paribus -- a child consuming daily or at least weekly chewing gum shows significantly less chance for OME than a child who seldom consumes or consumes no chewing gum (p = 0.023).

CONCLUSIONS

In the case of regular use of chewing gum, the probability of having OME in children is reduced by 40%. It seems plausible that children with immature oral motorics do not like chewing gum.

Auditory processing disorders: acquisition and treatment

Auditory processing disorder (APD) describes a mixed and poorly understood listening problem characterised by poor speech perception, especially in challenging environments. APD may include an inherited component, and this may be major, but studies reviewed here of children with long-term otitis media with effusion (OME) provide strong evidence for changes in auditory processing acquired through altered experience (deprivation) and brain plasticity. Whether inherited or acquired, it is suggested that APD may be reversed by active learning. Training tunes both bottom-up and top-down neural mechanisms, some that are specific to the trained stimulus and some that reflect more generalised arousal. APD and its treatment therefore provide examples of brain plasticity working either in a negative or in a positive way to modulate listening.

LEARNING OUTCOMES

(1) Readers will be able to discuss APD in the context of inheritance and experience. (2) Readers will be able to explain how OME has been shown to alter auditory processing. (3) Readers will be able to list examples of good and bad brain plasticity. (4) Readers will be able to explain what auditory learning is, list some of its properties, and provide examples of its application in therapy for communication disorders.

Auditory processing disorder (APD)-potential contribution of mouse research

APD is a common, heterogeneous and poorly understood listening impairment that is receiving increasing recognition, especially in children and the elderly. The primary symptom in humans is poor speech perception despite normal pure tone audiometry. Diagnostic practice is patchy, but current proposals are to distinguish APD by reduced ability to detect, discriminate, localize and order non-speech sounds. APD appears to result predominantly from core malfunctioning of the central auditory system, but with strong cognitive influences and possible additional influences from peripheral auditory and crossmodal sources. APD may be acquired (e.g. through middle ear disease), but it is likely that a more common etiology would involve both environmental and inherited contributions. Mice are increasingly being used for studies of central auditory processing. Most work to date has documented the basic response properties of auditory neurons, or used single gene mutations to investigate specific functions. For high throughput, primary screening, reflex and/or event-related potential measures are required. Pre-pulse inhibition (PPI), the regulation of an acoustic startle reflex by a preceding sound having distinct spatial, temporal or spectral properties, is one way in which auditory processing may be screened. For secondary assessment, standard psychoacoustic tests for mice have been developed.

[Hypoacusis after the neonatal period. Situations requiring hearing assessment]

INTRODUCTION

Because hearing plays a major role in language development, pediatric hypoacusis is especially damaging. The high frequency of hearing impairment in newborns and the need for an early diagnosis have led to the establishment of neonatal screening. Nevertheless, there are other situations which may compromise hearing quality in later stages and it is essential to identify them in order to be able to provide early and effective treatment.

OBJECTIVES

To describe the most frequent reasons for referring patients for hearing evaluation to a third level hospital and to identify common situations that require hearing assessment among the pediatric population.

PATIENTS AND METHODS

The clinical histories of 197 non-neonates evaluated for hypoacusis were reviewed. Clinical parameters and diagnosis were compared in patients with impaired and normal hearing.

RESULTS

One hundred sixty-one patients had no previous known hypoacusis. The main reason for evaluation was suspicion by the family or child minder (53.4 %), followed by language underdevelopment. In the first examinations 78 children had hypoacusis (48.4 %), which was more frequently bilateral than unilateral. In 29.5 % of hypoacusic patients, the disease was related to recurrent otitis or adenoiditis and in 25.6 % it was genetic. The most frequent antecedent was deaf relatives in hypoacusic patients and abnormal phenotypes in children with normal hearing. Three patients with previous bacterial meningitis were studied and two of these had hypoacusis.

CONCLUSIONS

Hypoacusic evaluation outside the context of newborn screening is mainly motivated by clinical suspicion of hypoacusis or language underdevelopment. Other situations such as recurrent otitis with effusion, syndromic phenotypic characteristics or bacterial meningitis are related to hearing problems and therefore require detailed evaluation.

Functional tubal therapy for persistent otitis media with effusion in children: myth or evidence?

Otitis media with effusion (OME), a form of inflammatory middle ear disease, is a common reason for young children to visit their family doctor and to have surgery. Tubal dysfunction plays a major role in the pathogenesis. In case of persistent OME, there seems to be a logical rationale for a favourable effect on the tubal dysfunction of a functional active motoric approach combined with behavioral changes (hygiene), and as a consequence for a therapeutic effect on the middle ear disease. The basic principles of this functional treatment are: active ventilation of the middle ear, correction of immature and undesirable deviant mouth habits, increasing swallowing frequency, activating jaw and palate movements, and encouraging the use of chewing gum. The bases for this functional therapy are critically analysed, and it may be concluded that all of these principles rely upon evidence based physiological mechanisms. However, the limited available clinical data from the literature are reviewed, and appear as methodologically weak. The results of an own prospective randomized pilot study comparing functional treatment with watchful waiting may be considered encouraging, since a borderline significance level was reached with a small amount of subjects.

Individual differences in auditory processing in specific language impairment: a follow-up study using event-related potentials and behavioural thresholds

It has frequently been claimed that children with specific language impairment (SLI) have impaired auditory perception, but there is much controversy about the role of such deficits in causing their language problems, and it has been difficult to establish solid, replicable findings in this area. Discrepancies in this field may arise because (a) a focus on mean results obscures the heterogeneity in the population and (b) insufficient attention has been paid to maturational aspects of auditory processing. We conducted a study of 16 young people with specific language impairment (SLI) and 16 control participants, 24 of whom had had auditory event-related potentials (ERPs) and frequency discrimination thresholds assessed 18 months previously. When originally assessed, around one third of the listeners with SLI had poor behavioural frequency discrimination thresholds, and these tended to be the younger participants. However, most of the SLI group had age-inappropriate late components of the auditory ERP, regardless of their frequency discrimination. At follow-up, the behavioural thresholds of those with poor frequency discrimination improved, though some remained outside the control range. At follow-up, ERPs for many of the individuals in the SLI group were still not age-appropriate. In several cases, waveforms of individuals in the SLI group resembled those of younger typically-developing children, though in other cases the waveform was unlike that of control cases at any age. Electrophysiological methods may reveal underlying immaturity or other abnormality of auditory processing even when behavioural thresholds look normal. This study emphasises the variability seen in SLI, and the importance of studying individual cases rather than focusing on group means.

Effects of otitis media with effusion on auditory temporal resolution

OBJECTIVE

There is mounting evidence to suggest that otitis media with effusion (OME) is associated with auditory processing deficits that persist beyond the resolution of the peripheral hearing loss. This study investigated the residual effects of OME on auditory temporal resolution. EXPERIMENT 1:

METHODS

Experiment 1 measured detection thresholds for a brief tone presented either before (backward masking) or during (simultaneous masking) a masking noise, in 6- and 8-year-old children. Six-year-olds were selected from a prospectively studied group with a lifetime known history of OME. Eight-year-old children, with a retrospectively determined history of OME, were also recruited. All children were free of OME at the time of testing.

RESULTS

Regardless of OME history, 6-year-old children had similar tone thresholds on all masking tasks. In contrast, 8-year-olds with a history of recurrent OME had 18 and 4dB higher mean thresholds for the backward and simultaneous masking conditions, respectively, compared with age-matched controls. Possible explanations for these results included (i) recruitment bias, rather than OME, contributed to differences in auditory processing abilities amongst 8-year-old children, or (ii) OME impaired performance at both ages, but this was not seen in 6-year-olds due to 'ceiling' effects. EXPERIMENT 2:

METHODS

To distinguish between these possibilities, Experiment 2 measured temporal resolution, using backward masking and amplitude modulation detection, in the prospectively studied group of children when they were 8 years old.

RESULTS

Regardless of OME history, these 8-year-olds had similar auditory temporal processing abilities. Results from Experiment 2 suggested that recruitment bias was the most likely explanation for the difference in auditory processing abilities between 8-year-old children with and without a history of OME found in Experiment 1. Consistent with previous data, associations were found between backward masking, age and cognitive ability.

CONCLUSION

There is no evidence to suggest that OME effects temporal resolution after the recovery of normal pure-tone thresholds.

Otitis media, hearing loss, and language learning: controversies and current research

This article reviews research on the possible linkage of otitis media with effusion (OME) to children's hearing and development, identifies gaps, and directions for research, and discusses implications for healthcare practices. About half of children with an episode of OME experience a mild hearing loss while about 5-10% of children have moderate hearing loss. Recent prospective and randomized clinical trials suggest none to very small negative associations of OME to children's later language development. Based on both retrospective and prospective longitudinal studies, associations between OME and perceiving speech in noise and tasks that require equal binaural hearing have been reported but have not been adequately studied with regard to functional outcomes. Thus, on average, for typically developing children, OME may not be a substantial risk factor for later speech and language development or academic achievement. However, these conclusions should be interpreted cautiously, since most of these studies used OME rather than hearing loss as the independent variable (although hearing loss rather than OME is hypothesized to affect language development) and many studies did not control for important confounding variables such as socioeconomic status (SES).