The human auditory system: A timeline of development

Maturational delay in the brainstem auditory pathway of very preterm babies with apnoea

AIMS

To assess the maturational status of the brainstem auditory pathway in babies with apnoea of prematurity (AOP) at 33-34 weeks of postmenstrual age (PMA), an important time landmark at which AOP is resolved in most cases.

STUDY DESIGN

Compare brainstem auditory maturation between very preterm babies with AOP and those without AOP (non-AOP) at the same PMA 33-34 weeks to define differences.

RESULTS

The AOP group showed significantly longer latencies of waves III and V latency than the non-AOP group (p < 0.05 and 0.01). The I-V interval in the AOP group was significantly longer than in the non-AOP group (p < 0.001). The same was true for the I-III and III-V intervals (p < 0.001 and 0.05). Wave III amplitude was significantly smaller (p < 0.05), and wave V amplitude was moderately smaller than in the non-AOP. At PMA 33 weeks, waves III and V latencies and all intervals in the AOP group were significantly longer than in the non-AOP group (p < 0.05-0.001). At PMA 34 weeks, these wave latencies and intervals in the AOP group were still significantly longer than in the non-AOP group (p < 0.05-0.01). Wave III amplitude in the AOP group was significantly smaller at both PMA 33 and 34 weeks (p < 0.05 and 0.05).

CONCLUSIONS

Brainstem auditory maturation in AOP babies is delayed at PMA 33 weeks, and remains delayed at PMA 34 weeks. These findings highlight the importance of monitoring and adequate intervention strategies during PMA 33-34 weeks in AOP babies.

Sensorineural hearing impairment among preterm children: a Norwegian population-based study

OBJECTIVE

To investigate the risk for sensorineural hearing impairment (SNHI) in preterm infants, and to what extent the risk is attributed to perinatal morbidities and therapies.

DESIGN

Population-based cohort study using data from several nationwide registries.

SETTING

Norwegian birth cohort 1999-2014, with data on SNHI until 2019.

PARTICIPANTS

60 023 live-born preterm infants, divided in moderate-late preterm (MLP) infants (32-36 weeks), very preterm (VP) infants (28-31 weeks) and extremely preterm (EP) infants (22-27 weeks), and a reference group with all 869 797 term-born infants from the study period.

MAIN OUTCOME MEASURES

SNHI defined by selected ICD-10 codes, recorded during minimum 5-year observation period after birth.

RESULTS

The overall SNHI prevalence in the preterm cohort was 1.4% compared with 0.7% in the reference group. The adjusted risk ratios (95% CIs) for SNHI were 1.7 (1.5-1.8) in MLP infants, 3.3 (2.8-3.9) in VP infants and 7.6 (6.3-9.1) in EP infants. Among EP infants, decreasing gestational age was associated with a steep increase in the risk ratio of SNHI reaching 14.8 (7.7-28.7) if born at 22-23 weeks gestation. Among the VP and MLP infants, mechanical ventilation and antibiotic therapy had strongest association with increased risk of SNHI, but infants not receiving these therapies remained at increased risk. Among EP infants intracranial haemorrhage increased the already high risk for SNHI. We found no signs of delayed or late-onset SNHI in preterm infants.

CONCLUSION

Preterm birth is an independent risk factor for SNHI. Invasive therapies and comorbidities increase the risk, predominantly in infants born after 28 weeks gestation.

The Spatial Organization of Ascending Auditory Pathway Microstructural Maturation From Infancy Through Adolescence Using a Novel Fiber Tracking Approach

Auditory perception is established through experience-dependent stimuli exposure during sensitive developmental periods; however, little is known regarding the structural development of the central auditory pathway in humans. The present study characterized the regional developmental trajectories of the ascending auditory pathway from the brainstem to the auditory cortex from infancy through adolescence using a novel diffusion MRI-based tractography approach and along-tract analyses. We used diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) to quantify the magnitude and timing of auditory pathway microstructural maturation. We found spatially varying patterns of white matter maturation along the length of the tract, with inferior brainstem regions developing earlier than thalamocortical projections and left hemisphere tracts developing earlier than the right. These results help to characterize the processes that give rise to functional auditory processing and may provide a baseline for detecting abnormal development.

Validating a novel paradigm for simultaneously assessing mismatch response and frequency-following response to speech sounds

BACKGROUND

Speech sounds are processed in the human brain through intricate and interconnected cortical and subcortical structures. Two neural signatures, one largely from cortical sources (mismatch response, MMR) and one largely from subcortical sources (frequency-following response, FFR) are critical for assessing speech processing as they both show sensitivity to high-level linguistic information. However, there are distinct prerequisites for recording MMR and FFR, making them difficult to acquire simultaneously NEW METHOD: Using a new paradigm, our study aims to concurrently capture both signals and test them against the following criteria: (1) replicating the effect that the MMR to a native speech contrast significantly differs from the MMR to a nonnative speech contrast, and (2) demonstrating that FFRs to three speech sounds can be reliably differentiated.

RESULTS

Using EEG from 18 adults, we observed a decoding accuracy of 72.2 % between the MMR to native vs. nonnative speech contrasts. A significantly larger native MMR was shown in the expected time window. Similarly, a significant decoding accuracy of 79.6 % was found for FFR. A high stimulus-to-response cross-correlation with a 9 ms lag suggested that FFR closely tracks speech sounds.

COMPARISON WITH EXISTING METHOD(S)

These findings demonstrate that our paradigm reliably captures both MMR and FFR concurrently, replicating and extending past research with much fewer trials (MMR: 50 trials; FFR: 200 trials) and shorter experiment time (12 minutes).

CONCLUSIONS

This study paves the way to understanding cortical-subcortical interactions for speech and language processing, with the ultimate goal of developing an assessment tool specific to early development.

Auditory Effects of Acoustic Noise From 3-T Brain MRI in Neonates With Hearing Protection

BACKGROUND

Neonates with immature auditory function (eg, weak/absent middle ear muscle reflex) could conceivably be vulnerable to noise-induced hearing loss; however, it is unclear if neonates show evidence of hearing loss following MRI acoustic noise exposure.

PURPOSE

To explore the auditory effects of MRI acoustic noise in neonates.

STUDY TYPE

Prospective.

SUBJECTS

Two independent cohorts of neonates (N = 19 and N = 18; mean gestational-age, 38.75 ± 2.18 and 39.01 ± 1.83 weeks).

FIELD STRENGTH/SEQUENCE

T1-weighted three-dimensional gradient-echo sequence, T2-weighted fast spin-echo sequence, single-shot echo-planar imaging-based diffusion-tensor imaging, single-shot echo-planar imaging-based diffusion-kurtosis imaging and T2-weighted fluid-attenuated inversion recovery sequence at 3.0 T.

ASSESSMENT

All neonates wore ear protection during scan protocols lasted ~40 minutes. Equivalent sound pressure levels (SPLs) were measured for both cohorts. In cohort1, left- and right-ear auditory brainstem response (ABR) was measured before (baseline) and after (follow-up) MRI, included assessment of ABR threshold, wave I, III and V latencies and interpeak interval to determine the functional status of auditory nerve and brainstem. In cohort2, baseline and follow-up left- and right-ear distortion product otoacoustic emission (DPOAE) amplitudes were assessed at 1.2 to 7.0 kHz to determine cochlear function.

STATISTICAL TEST

Wilcoxon signed-rank or paired t-tests with Bonferroni's correction were used to compare the differences between baseline and follow-up ABR and DPOAE measures.

RESULTS

Equivalent SPLs ranged from 103.5 to 113.6 dBA. No significant differences between baseline and follow-up were detected in left- or right-ear ABR measures (P > 0.999, Bonferroni corrected) in cohort1, or in DPOAE levels at 1.2 to 7.0 kHz in cohort2 (all P > 0.999 Bonferroni corrected except for left-ear levels at 3.5 and 7.0 kHz with corrected P = 0.138 and P = 0.533).

DATA CONCLUSION

A single 40-minute 3-T MRI with equivalent SPLs of 103.5-113.6 dBA did not result in significant transient disruption of auditory function, as measured by ABR and DPOAE, in neonates with adequate hearing protection.

EVIDENCE LEVEL

2.

TECHNICAL EFFICACY

Stage 5.

Longitudinal trajectories of the neural encoding mechanisms of speech-sound features during the first year of life

Infants quickly recognize the sounds of their mother language, perceiving the spectrotemporal acoustic features of speech. However, the underlying neural machinery remains unclear. We used an auditory evoked potential termed frequency-following response (FFR) to unravel the neural encoding maturation for two speech sound characteristics: voice pitch and temporal fine structure. 37 healthy-term neonates were tested at birth and retested at the ages of six and twelve months. Results revealed a reduction in neural phase-locking onset to the stimulus envelope from birth to six months, stabilizing by twelve months. While neural encoding of voice pitch remained consistent across ages, temporal fine structure encoding matured rapidly from birth to six months, without further improvement from six to twelve months. Results highlight the critical importance of the first six months of life in the maturation of neural encoding mechanisms that are crucial for phoneme discrimination during early language acquisition.

The spatial organization of ascending auditory pathway microstructural maturation from infancy through adolescence using a novel fiber tracking approach

Auditory perception is established through experience-dependent stimuli exposure during sensitive developmental periods; however, little is known regarding the structural development of the central auditory pathway in humans. The present study characterized the regional developmental trajectories of the ascending auditory pathway from the brainstem to the auditory cortex from infancy through adolescence using a novel diffusion MRI-based tractography approach and along-tract analyses. We used diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) to quantify the magnitude and timing of auditory pathway microstructural maturation. We found spatially varying patterns of white matter maturation along the length of the tract, with inferior brainstem regions developing earlier than thalamocortical projections and left hemisphere tracts developing earlier than the right. These results help to characterize the processes that give rise to functional auditory processing and may provide a baseline for detecting abnormal development.

Electrophysiological responses of audiovisual integration from infancy to adulthood

Our ability to merge information from different senses into a unified percept is a crucial perceptual process for efficient interaction with our multisensory environment. Yet, the developmental process underlying how the brain implements multisensory integration (MSI) remains poorly known. This cross-sectional study aims to characterize the developmental patterns of audiovisual events in 131 individuals aged from 3 months to 30 years. Electroencephalography (EEG) was recorded during a passive task, including simple auditory, visual, and audiovisual stimuli. In addition to examining age-related variations in MSI responses, we investigated Event-Related Potentials (ERPs) linked with auditory and visual stimulation alone. This was done to depict the typical developmental trajectory of unisensory processing from infancy to adulthood within our sample and to contextualize the maturation effects of MSI in relation to unisensory development. Comparing the neural response to audiovisual stimuli to the sum of the unisensory responses revealed signs of MSI in the ERPs, more specifically between the P2 and N2 components (P2 effect). Furthermore, adult-like MSI responses emerge relatively late in the development, around 8 years old. The automatic integration of simple audiovisual stimuli is a long developmental process that emerges during childhood and continues to mature during adolescence with ERP latencies decreasing with age.

Visual and auditory attention in individuals with DYRK1A and SCN2A disruptive variants

This preliminary study sought to assess biomarkers of attention using electroencephalography (EEG) and eye tracking in two ultra-rare monogenic populations associated with autism spectrum disorder (ASD). Relative to idiopathic ASD (n = 12) and neurotypical comparison (n = 49) groups, divergent attention profiles were observed for the monogenic groups, such that individuals with DYRK1A (n = 9) exhibited diminished auditory attention condition differences during an oddball EEG paradigm whereas individuals with SCN2A (n = 5) exhibited diminished visual attention condition differences noted by eye gaze tracking when viewing social interactions. Findings provide initial support for alignment of auditory and visual attention markers in idiopathic ASD and neurotypical development but not monogenic groups. These results support ongoing efforts to develop translational ASD biomarkers within the attention domain.

Vocal and early speech development in Korean-acquiring children with hearing loss and typical hearing

This study investigated the vocal and early speech development of Korean-acquiring children with hearing loss (HL) who underwent early auditory amplification compared to their typical hearing (TH) counterparts. The research focused on phonological characteristics of child vocalisation based on samples collected from naturalistic home environments. One-day home recordings using a Language ENvironment Analysis (LENA) recorder were obtained from 6 children with HL and 12 children with TH who ranged from 17 to 23 months of age in Korean monolingual environments. Child volubility, canonical babbling ratio (CBR), consonant distributions, and utterance structures of vocalisations were evaluated through qualitative and quantitative analyses of vocalisation samples collected from LENA recordings. The findings revealed that children with HL displayed comparable vocalisation levels to children with TH, with no significant differences in volubility and CBR. In consonant and utterance shape inventories, noticeable quantitative and qualitative differences were observed between children with HL and those with TH. The study also suggested both universal and language-specific production patterns, revealing the early effects of ambient language on consonant distributions and utterance structures within their vocalisation repertoire. This study emphasised the role of auditory input and the importance of early auditory amplification to support speech development in children with HL.

Trajectories of brain and behaviour development in the womb, at birth and through infancy

Birth is often seen as the starting point for studying effects of the environment on human development, with much research focused on the capacities of young infants. However, recent imaging advances have revealed that the complex behaviours of the fetus and the uterine environment exert influence. Birth is now viewed as a punctuate event along a developmental pathway of increasing autonomy of the child from their mother. Here we highlight (1) increasing physiological autonomy and perceptual sensitivity in the fetus, (2) physiological and neurochemical processes associated with birth that influence future behaviour, (3) the recalibration of motor and sensory systems in the newborn to adapt to the world outside the womb and (4) the effect of the prenatal environment on later infant behaviours and brain function. Taken together, these lines of evidence move us beyond nature-nurture issues to a developmental human lifespan view beginning within the womb.

The maturation of infant and toddler visual cortex neural activity and associations with fine motor performance

Our understanding of how visual cortex neural processes mature during infancy and toddlerhood is limited. Using magnetoencephalography (MEG), the present study investigated the development of visual evoked responses (VERs) in both cross-sectional and longitudinal samples of infants and toddlers 2 months to 3 years. Brain space analyses focused on N1m and P1m latency, as well as the N1m-to-P1m amplitude. Associations between VER measures and developmental quotient (DQ) scores in the cognitive/visual and fine motor domains were also examined. Results showed a nonlinear decrease in N1m and P1m latency as a function of age, characterized by rapid changes followed by slower progression, with the N1m latency plateauing at 6-7 months and the P1m latency plateauing at 8-9 months. The N1m-to-P1m amplitude also exhibited a non-linear decrease, with strong responses observed in younger infants (∼2-3 months) and then a gradual decline. Associations between N1m and P1m latency and fine motor DQ scores were observed, suggesting that infants with faster visual processing may be better equipped to perform fine motor tasks. The present findings advance our understanding of the maturation of the infant visual system and highlight the relationship between the maturation of visual system and fine motor skills.

Highlights

The infant N1m and P1m latency shows a nonlinear decrease.N1m latency decreases precede P1m latency decreases.N1m-to-P1m amplitude shows a nonlinear decrease, with stronger responses in younger than older infants.N1m and P1m latency are associated with fine motor DQ.

Examining the relationship of acetaminophen use during pregnancy with early language development in children

BACKGROUND

Acetaminophen is the only analgesic considered safe for use throughout pregnancy. Recent studies suggest that use during pregnancy may be associated with poorer neurodevelopmental outcomes in children, but few have examined language development.

METHODS

The Illinois Kids Development Study is a prospective birth cohort in east-central Illinois. Between December 2013 and March 2020, 532 newborns were enrolled and had exposure data available. Participants reported the number of times they took acetaminophen six times across pregnancy. Language data were collected at 26.5-28.5 months using the MacArthur-Bates Communicative Development Inventories (CDI; n = 298), and 36-38 months using the Speech and Language Assessment Scale (SLAS; n = 254).

RESULTS

Taking more acetaminophen during the second or third trimester was associated with marginally smaller vocabularies and shorter utterance length (M3L) at 26.5-28.5 months. More acetaminophen use during the third trimester was also associated with increased odds of M3L scores ≤25th percentile in male children. More use during the second or third trimester was associated with lower SLAS scores at 36-38 months. Third trimester use was specifically related to lower SLAS scores in male children.

CONCLUSIONS

Higher prenatal acetaminophen use during pregnancy may be associated with poorer early language development.

IMPACT

Taking more acetaminophen during pregnancy, particularly during the second and third trimesters, was associated with poorer scores on measures of language development when children were 26.5-28.5 and 36-38 months of age. Only male children had lower scores in analyses stratified by child sex. To our knowledge, this is the first study that has used a standardized measure of language development to assess the potential impact of prenatal exposure to acetaminophen on language development. This study adds to the growing body of literature suggesting that the potential impact of acetaminophen use during pregnancy on fetal neurodevelopment should be carefully evaluated.

Exposure to bilingual or monolingual maternal speech during pregnancy affects the neurophysiological encoding of speech sounds in neonates differently

Introduction

Exposure to maternal speech during the prenatal period shapes speech perception and linguistic preferences, allowing neonates to recognize stories heard frequently in utero and demonstrating an enhanced preference for their mother's voice and native language. Yet, with a high prevalence of bilingualism worldwide, it remains an open question whether monolingual or bilingual maternal speech during pregnancy influence differently the fetus' neural mechanisms underlying speech sound encoding.

Methods

In the present study, the frequency-following response (FFR), an auditory evoked potential that reflects the complex spectrotemporal dynamics of speech sounds, was recorded to a two-vowel /oa/ stimulus in a sample of 129 healthy term neonates within 1 to 3 days after birth. Newborns were divided into two groups according to maternal language usage during the last trimester of gestation (monolingual; bilingual). Spectral amplitudes and spectral signal-to-noise ratios (SNR) at the stimulus fundamental (F0) and first formant (F1) frequencies of each vowel were, respectively, taken as measures of pitch and formant structure neural encoding.

Results

Our results reveal that while spectral amplitudes at F0 did not differ between groups, neonates from bilingual mothers exhibited a lower spectral SNR. Additionally, monolingually exposed neonates exhibited a higher spectral amplitude and SNR at F1 frequencies.

Discussion

We interpret our results under the consideration that bilingual maternal speech, as compared to monolingual, is characterized by a greater complexity in the speech sound signal, rendering newborns from bilingual mothers more sensitive to a wider range of speech frequencies without generating a particularly strong response at any of them. Our results contribute to an expanding body of research indicating the influence of prenatal experiences on language acquisition and underscore the necessity of including prenatal language exposure in developmental studies on language acquisition, a variable often overlooked yet capable of influencing research outcomes.

The frequency-following response in late preterm neonates: a pilot study

Introduction

Infants born very early preterm are at high risk of language delays. However, less is known about the consequences of late prematurity. Hence, the aim of the present study is to characterize the neural encoding of speech sounds in late preterm neonates in comparison with those born at term.

Methods

The speech-evoked frequency-following response (FFR) was recorded to a consonant-vowel stimulus /da/ in 36 neonates in three different groups: 12 preterm neonates [mean gestational age (GA) 36.05 weeks], 12 "early term neonates" (mean GA 38.3 weeks), and "late term neonates" (mean GA 41.01 weeks).

Results

From the FFR recordings, a delayed neural response and a weaker stimulus F0 encoding in premature neonates compared to neonates born at term was observed. No differences in the response time onset nor in stimulus F0 encoding were observed between the two groups of neonates born at term. No differences between the three groups were observed in the neural encoding of the stimulus temporal fine structure.

Discussion

These results highlight alterations in the neural encoding of speech sounds related to prematurity, which were present for the stimulus F0 but not for its temporal fine structure.

Brain Signatures of Early and Late Neural Measures of Auditory Habituation and Discrimination in Autism and Their Relationship to Autistic Traits and Sensory Overresponsivity

Sensory differences are included in the DSM-5 criteria of autism for the first time, yet it is unclear how they relate to neural indicators of perception. We studied early brain signatures of perception and examined their relationship to sensory behaviors and autistic traits. Thirteen autistic children and 13 Typically Developing (TD) children matched on age and nonverbal IQ participated in a passive oddball task, during which P1 habituation and P1 and MMN discrimination were evoked by pure tones. Autistic children had less neural habituation than the TD comparison group, and the MMN, but not P1, mapped on to sensory overresponsivity. Findings highlight the significance of temporal and contextual factors in neural information processing as it relates to autistic traits and sensory behaviors.

Unveiling the development of human voice perception: Neurobiological mechanisms and pathophysiology

The human voice is a critical stimulus for the auditory system that promotes social connection, informs the listener about identity and emotion, and acts as the carrier for spoken language. Research on voice processing in adults has informed our understanding of the unique status of the human voice in the mature auditory cortex and provided potential explanations for mechanisms that underly voice selectivity and identity processing. There is evidence that voice perception undergoes developmental change starting in infancy and extending through early adolescence. While even young infants recognize the voice of their mother, there is an apparent protracted course of development to reach adult-like selectivity for human voice over other sound categories and recognition of other talkers by voice. Gaps in the literature do not allow for an exact mapping of this trajectory or an adequate description of how voice processing and its neural underpinnings abilities evolve. This review provides a comprehensive account of developmental voice processing research published to date and discusses how this evidence fits with and contributes to current theoretical models proposed in the adult literature. We discuss how factors such as cognitive development, neural plasticity, perceptual narrowing, and language acquisition may contribute to the development of voice processing and its investigation in children. We also review evidence of voice processing abilities in premature birth, autism spectrum disorder, and phonagnosia to examine where and how deviations from the typical trajectory of development may manifest.

On the interplay between speech perception and production: insights from research and theories

The study of spoken communication has long been entrenched in a debate surrounding the interdependence of speech production and perception. This mini review summarizes findings from prior studies to elucidate the reciprocal relationships between speech production and perception. We also discuss key theoretical perspectives relevant to speech perception-production loop, including hyper-articulation and hypo-articulation (H&H) theory, speech motor theory, direct realism theory, articulatory phonology, the Directions into Velocities of Articulators (DIVA) and Gradient Order DIVA (GODIVA) models, and predictive coding. Building on prior findings, we propose a revised auditory-motor integration model of speech and provide insights for future research in speech perception and production, focusing on the effects of impaired peripheral auditory systems.

An auditory perspective on phonological development in infancy

Introduction

The auditory system encodes the phonetic features of languages by processing spectro-temporal modulations in speech, which can be described at two time scales: relatively slow amplitude variations over time (AM, further distinguished into the slowest <8-16 Hz and faster components 16-500 Hz), and frequency modulations (FM, oscillating at higher rates about 600-10 kHz). While adults require only the slowest AM cues to identify and discriminate speech sounds, infants have been shown to also require faster AM cues (>8-16 Hz) for similar tasks.

Methods

Using an observer-based psychophysical method, this study measured the ability of typical-hearing 6-month-olds, 10-month-olds, and adults to detect a change in the vowel or consonant features of consonant-vowel syllables when temporal modulations are selectively degraded. Two acoustically degraded conditions were designed, replacing FM cues with pure tones in 32 frequency bands, and then extracting AM cues in each frequency band with two different low-pass cut- off frequencies: (1) half the bandwidth (Fast AM condition), (2) <8 Hz (Slow AM condition).

Results

In the Fast AM condition, results show that with reduced FM cues, 85% of 6-month-olds, 72.5% of 10-month-olds, and 100% of adults successfully categorize phonemes. Among participants who passed the Fast AM condition, 67% of 6-month-olds, 75% of 10-month-olds, and 95% of adults passed the Slow AM condition. Furthermore, across the three age groups, the proportion of participants able to detect phonetic category change did not differ between the vowel and consonant conditions. However, age-related differences were observed for vowel categorization: while the 6- and 10-month-old groups did not differ from one another, they both independently differed from adults. Moreover, for consonant categorization, 10-month-olds were more impacted by acoustic temporal degradation compared to 6-month-olds, and showed a greater decline in detection success rates between the Fast AM and Slow AM conditions.

Discussion

The degradation of FM and faster AM cues (>8 Hz) appears to strongly affect consonant processing at 10 months of age. These findings suggest that between 6 and 10 months, infants show different developmental trajectories in the perceptual weight of speech temporal acoustic cues for vowel and consonant processing, possibly linked to phonological attunement.

Probing Beat Perception with Event-Related Potentials (ERPs) in Human Adults, Newborns, and Nonhuman Primates

The aim of this chapter is to give an overview of how the perception of rhythmic temporal regularity such as a regular beat in music can be studied in human adults, human newborns, and nonhuman primates using event-related brain potentials (ERPs). First, we discuss different aspects of temporal structure in general, and musical rhythm in particular, and we discuss the possible mechanisms underlying the perception of regularity (e.g., a beat) in rhythm. Additionally, we highlight the importance of dissociating beat perception from the perception of other types of structure in rhythm, such as predictable sequences of temporal intervals, ordinal structure, and rhythmic grouping. In the second section of the chapter, we start with a discussion of auditory ERPs elicited by infrequent and frequent sounds: ERP responses to regularity violations, such as mismatch negativity (MMN), N2b, and P3, as well as early sensory responses to sounds, such as P1 and N1, have been shown to be instrumental in probing beat perception. Subsequently, we discuss how beat perception can be probed by comparing ERP responses to sounds in regular and irregular sequences, and by comparing ERP responses to sounds in different metrical positions in a rhythm, such as on and off the beat or on strong and weak beats. Finally, we will discuss previous research that has used the aforementioned ERPs and paradigms to study beat perception in human adults, human newborns, and nonhuman primates. In doing so, we consider the possible pitfalls and prospects of the technique, as well as future perspectives.

Spectral Resolution and Speech Perception in Cochlear Implanted School-Aged Children

OBJECTIVE

Cochlear implantation of prelingually deaf infants provides auditory input sufficient to develop spoken language; however, outcomes remain variable. Inability to participate in speech perception testing limits testing device efficacy in young listeners. In postlingually implanted adults (aCI), speech perception correlates with spectral resolution an ability that relies independently on frequency resolution (FR) and spectral modulation sensitivity (SMS). The correlation of spectral resolution to speech perception is unknown in prelingually implanted children (cCI). In this study, FR and SMS were measured using a spectral ripple discrimination (SRD) task and were correlated with vowel and consonant identification. It was hypothesized that prelingually deaf cCI would show immature SMS relative to postlingually deaf aCI and that FR would correlate with speech identification.

STUDY DESIGN

Cross-sectional study.

SETTING

In-person, booth testing.

METHODS

SRD was used to determine the highest spectral ripple density perceived at various modulation depths. FR and SMS were derived from spectral modulation transfer functions. Vowel and consonant identification was measured; SRD performance and speech identification were analyzed for correlation.

RESULTS

Fifteen prelingually implanted cCI and 13 postlingually implanted aCI were included. FR and SMS were similar between cCI and aCI. Better FR was associated with better speech identification for most measures.

CONCLUSION

Prelingually implanted cCI demonstrated adult-like FR and SMS; additionally, FR correlated with speech identification. FR may be a measure of CI efficacy in young listeners.

Structural networking of the developing brain: from maturation to neurosurgical implications

Modern neuroscience agrees that neurological processing emerges from the multimodal interaction among multiple cortical and subcortical neuronal hubs, connected at short and long distance by white matter, to form a largely integrated and dynamic network, called the brain "connectome." The final architecture of these circuits results from a complex, continuous, and highly protracted development process of several axonal pathways that constitute the anatomical substrate of neuronal interactions. Awareness of the network organization of the central nervous system is crucial not only to understand the basis of children's neurological development, but also it may be of special interest to improve the quality of neurosurgical treatments of many pediatric diseases. Although there are a flourishing number of neuroimaging studies of the connectome, a comprehensive vision linking this research to neurosurgical practice is still lacking in the current pediatric literature. The goal of this review is to contribute to bridging this gap. In the first part, we summarize the main current knowledge concerning brain network maturation and its involvement in different aspects of normal neurocognitive development as well as in the pathophysiology of specific diseases. The final section is devoted to identifying possible implications of this knowledge in the neurosurgical field, especially in epilepsy and tumor surgery, and to discuss promising perspectives for future investigations.

Auditory Cortex Maturation and Language Development in Children with Hearing Loss and Additional Disabilities

A significant portion of hearing-impaired children have additional disabilities, but data about the maturation of their auditory cortex are scarce. In these children, behavioral tests are often unreliable, and objective tests are needed for diagnostics and follow-up. This study aimed to explore auditory cortical maturation and language development, and the usability of an objective electroencephalogram-based biomarker in children with multiple disabilities. In 65 hearing aid and cochlear implant users (36 females; 36 with multiple disabilities; 44.3 ± 18.5 months of age, mean ± SD), auditory processing was examined using the P1 cortical auditory evoked response biomarker, and language development with the Preschool Language Scales 5th edition (PLS-5). During the study, all of the children received intensive extra language therapy for six months. No significant differences were found between the groups in P1 latency development, the proportion of abnormal P1 latencies, or the number of children whose P1 latencies changed from abnormal to normal during the study. The PLS-5 total language scores, auditory comprehension scores, or expressive communication scores did not differ between groups either. The P1 latencies showed meaningful negative correlations with the language scores. The results suggest that auditory cortex development is similar in hearing-impaired children with/without additional disabilities, and the P1 biomarker is a feasible tool to evaluate central auditory maturation in children with multiple disabilities.

Impact of Prematurity on Auditory Processing in Children

Prematurity is one of the most crucial risk factors negatively affecting the maturation of the auditory system. Children born preterm demonstrate high rates of hearing impairments. Auditory processing difficulties in preterm children might be a result of disturbances in the central auditory system development and/or sensory deprivation due to peripheral hearing loss. To investigate auditory processing in preterm children, we utilized a set of psychoacoustic tests to assess temporal processing and speech intelligibility. A total of 241 children aged 6-11 years old (136 born preterm and 105 healthy full-term children forming the control group) were assessed. The preterm children were divided into three groups based on their peripheral hearing status: 74 normal hearing (NH group); 30 children with bilateral permanent sensorineural hearing loss (SNHL group) and 32 children with bilateral auditory neuropathy spectrum disorder (ANSD group). The results showed significantly worse performance in all tests in premature children compared with full-term children. NH and SNHL groups showed significant age-related improvement in speech recognition thresholds in noise that might signify a "bottom-up" auditory processing maturation effect. Overall, all premature children had signs of auditory processing disorders of varying degrees. Analyzing and understanding the auditory processing specificity in preterm children can positively contribute to the more effective implementation of rehabilitation programs.

Divergent auditory activation in relation to inhibition task performance in children and adults

Adults and children show remarkable differences in cortical auditory activation which, in children, have shown relevance for cognitive performance, specifically inhibitory control. However, it has not been tested whether these differences translate to functional differences in response inhibition between adults and children. We recorded auditory responses of adults and school-aged children (6-14 years) using combined magneto- and electroencephalography (M/EEG) during passive listening conditions and an auditory Go/No-go task. The associations between auditory cortical responses and inhibition performance measures diverge between adults and children; while in children the brain-behavior associations are not significant, or stronger responses are beneficial, adults show negative associations between auditory cortical responses and inhibitory performance. Furthermore, we found differences in brain responses between adults and children; the late (~200 ms post stimulation) adult peak activation shifts from auditory to frontomedial areas. In contrast, children show prolonged obligatory responses in the auditory cortex. Together this likely translates to a functional difference between adults and children in the cortical resources for performance consistency in auditory-based cognitive tasks.

Differential Maturation of Auditory Cortex Activity in Young Children with Autism and Typical Development

Maturation of auditory cortex neural encoding processes was assessed in children with typical development (TD) and autism. Children 6-9 years old were enrolled at Time 1 (T1), with follow-up data obtained ~ 18 months later at Time 2 (T2), and ~ 36 months later at Time 3 (T3). Findings suggested an initial period of rapid auditory cortex maturation in autism, earlier than TD (prior to and surrounding the T1 exam), followed by a period of faster maturation in TD than autism (T1-T3). As a result of group maturation differences, post-stimulus group differences were observed at T1 but not T3. In contrast, stronger pre-stimulus activity in autism than TD was found at all time points, indicating this brain measure is stable across time.

Altered maturation in brainstem neural conduction in very premature babies with fetal growth restriction

BACKGROUND

Using maximum length sequence brainstem auditory evoked response (MLS BAER) to study brainstem neural conduction and maturation in fetal growth restriction (FGR) babies born very prematurely and assess the effect of FGR on brainstem neural maturation.

METHODS

MLS BAER was recorded and analyzed at a mean 40 week postmenstrual age in babies born at 27-32 week gestation without other major perinatal conditions or problems. The data were compared between babies with FGR (n = 30) and age-matched babies without FGR (n = 34) to define any differences.

RESULTS

A notable difference in MLS BAER was found in interpeak intervals between the babies with FGR and those without FGR. The FGR babies manifested significantly shortened I-III interval, moderately prolonged III-V interval, and significantly decreased III-V/I-III interval ratio. The slope of the I-III interval-rate function in FGR babies was moderately decreased, relative to that in the babies without FGR.

CONCLUSION

FGR babies born very prematurely are associated with accelerated or precocial neural maturation at caudal brainstem regions, but moderately delayed maturation at rostral brainstem regions. The altered brainstem neural maturation is different from previously reported mildly delayed maturation in FGR babies born less prematurely, and may have important implication for neurodevelopmental outcome.

IMPACT

This first MLS BAER study in FGR found that brainstem neural maturation in very premature FGR babies differed from age-matched non-FGR babies. Neural maturation in very premature FGR babies is accelerated or precocial at caudal brainstem regions but moderately delayed at rostral brainstem regions. The altered maturation is different from previously reported mild delay in brainstem neural maturation in FGR babies born less prematurely. FGR exerts a major and differential effect on brainstem neural maturation in babies born very prematurely. This alteration in very premature FGR babies may have important implication for their neurodevelopment.

Occupational and environmental noise exposure during pregnancy and rare health outcomes of offspring: a scoping review focusing on congenital anomalies and perinatal mortality

As environmental and occupational noise can be health hazards, recent studies have investigated the effects of noise exposure during pregnancy. Despite biological plausibility and animal studies supporting an association, studies focusing on congenital anomalies and perinatal mortality as outcomes of noise exposure are still scarce. We performed a scoping review to collect, summarise, and discuss the existing scientific research about the relationships between noise exposure during pregnancy and congenital anomalies and/or perinatal mortality. We searched electronic databases for papers published between 1970 and March 2021. We included 16 studies (seven on congenital anomalies, three on perinatal mortality, and two on both congenital anomalies and perinatal mortality). We assessed four studies on congenital hearing dysfunction as the definition of congenital anomalies includes functional anomalies. We found few studies on this topic and no studies on the combined effects of occupational and environmental noise exposures. Evidence suggests a small increase in the risk of congenital anomalies in relation to occupational and to a lesser extent environmental noise exposure. In addition, few studies investigated perinatal mortality and the ones that did, used different outcome definitions, so no conclusions could be made. However, a recent big cross-sectional study demonstrated an association between road traffic noise and stillbirth. A few studies suggest a possible association between congenital hearing dysfunction and occupational noise exposure during pregnancy. Future studies with larger samples, better exposure assessments, and better statistical modelling strategies are needed to investigate these relationships further.

Neuroanatomical Disposition, Natural Development, and Training-Induced Plasticity of the Human Auditory System from Childhood to Adulthood: A 12-Year Study in Musicians and Nonmusicians

Auditory perception is fundamental to human development and communication. However, no long-term studies have been performed on the plasticity of the auditory system as a function of musical training from childhood to adulthood. The long-term interplay between developmental and training-induced neuroplasticity of auditory processing is still unknown. We present results from AMseL (Audio and Neuroplasticity of Musical Learning), the first longitudinal study on the development of the human auditory system from primary school age until late adolescence. This 12-year project combined neurologic and behavioral methods including structural magnetic resonance imaging (MRI), magnetoencephalography (MEG), and auditory tests. A cohort of 112 typically developing participants (51 male, 61 female), classified as "musicians" (n = 66) and "nonmusicians" (n = 46), was tested at five measurement timepoints. We found substantial, stable differences in the morphology of auditory cortex (AC) between musicians and nonmusicians even at the earliest ages, suggesting that musical aptitude is manifested in macroscopic neuroanatomical characteristics. Maturational plasticity led to a continuous increase in white matter myelination and systematic changes of the auditory evoked P1-N1-P2 complex (decreasing latencies, synchronization effects between hemispheres, and amplitude changes) regardless of musical expertise. Musicians showed substantial training-related changes at the neurofunctional level, in particular more synchronized P1 responses and bilaterally larger P2 amplitudes. Musical training had a positive influence on elementary auditory perception (frequency, tone duration, onset ramp) and pattern recognition (rhythm, subjective pitch). The observed interplay between "nature" (stable biological dispositions and natural maturation) and "nurture" (learning-induced plasticity) is integrated into a novel neurodevelopmental model of the human auditory system.Significance Statement We present results from AMseL (Audio and Neuroplasticity of Musical Learning), a 12-year longitudinal study on the development of the human auditory system from childhood to adulthood that combined structural magnetic resonance imaging (MRI), magnetoencephalography (MEG), and auditory discrimination and pattern recognition tests. A total of 66 musicians and 46 nonmusicians were tested at five timepoints. Substantial, stable differences in the morphology of auditory cortex (AC) were found between the two groups even at the earliest ages, suggesting that musical aptitude is manifested in macroscopic neuroanatomical characteristics. We also observed neuroplastic and perceptual changes with age and musical practice. This interplay between "nature" (stable biological dispositions and natural maturation) and "nurture" (learning-induced plasticity) is integrated into a novel neurodevelopmental model of the human auditory system.

Prenatal daily musical exposure is associated with enhanced neural representation of speech fundamental frequency: Evidence from neonatal frequency-following responses

Fetal hearing experiences shape the linguistic and musical preferences of neonates. From the very first moment after birth, newborns prefer their native language, recognize their mother's voice, and show a greater responsiveness to lullabies presented during pregnancy. Yet, the neural underpinnings of this experience inducing plasticity have remained elusive. Here we recorded the frequency-following response (FFR), an auditory evoked potential elicited to periodic complex sounds, to show that prenatal music exposure is associated to enhanced neural encoding of speech stimuli periodicity, which relates to the perceptual experience of pitch. FFRs were recorded in a sample of 60 healthy neonates born at term and aged 12-72 hours. The sample was divided into two groups according to their prenatal musical exposure (29 daily musically exposed; 31 not-daily musically exposed). Prenatal exposure was assessed retrospectively by a questionnaire in which mothers reported how often they sang or listened to music through loudspeakers during the last trimester of pregnancy. The FFR was recorded to either a /da/ or an /oa/ speech-syllable stimulus. Analyses were centered on stimuli sections of identical duration (113 ms) and fundamental frequency (F0  = 113 Hz). Neural encoding of stimuli periodicity was quantified as the FFR spectral amplitude at the stimulus F0 . Data revealed that newborns exposed daily to music exhibit larger spectral amplitudes at F0 as compared to not-daily musically-exposed newborns, regardless of the eliciting stimulus. Our results suggest that prenatal music exposure facilitates the tuning to human speech fundamental frequency, which may support early language processing and acquisition. RESEARCH HIGHLIGHTS: Frequency-following responses to speech were collected from a sample of neonates prenatally exposed to music daily and compared to neonates not-daily exposed to music. Neonates who experienced daily prenatal music exposure exhibit enhanced frequency-following responses to the periodicity of speech sounds. Prenatal music exposure is associated with a fine-tuned encoding of human speech fundamental frequency, which may facilitate early language processing and acquisition.

Melody of Vocants: Fixed Pattern or Shaped by Hearing?

INTRODUCTION

Vocants as infants' first vocalic utterances are produced laryngeally while the vocal tract is maintained in a neutral position. These "primitive" sounds have sometimes been described as largely innate and, therefore, as sounding alike in both healthy and hearing-impaired young infants.

OBJECTIVE

The objective of this study is to compare melody features of vocants, recorded during face-to-face interaction, between infants (N = 8) with profound congenital sensorineural hearing loss (HI group) and age-matched (N = 18) controls (CO) group. The question was as follows: does a lack of auditory feedback have a noticeable effect on melodic features of vocants?

METHODS

The cooing database totalled 6,998 vocalizations (HI: N = 2,847; CO: N = 4,151), all of which had been recorded during the observation period of 60-181 days of age. Identification of the vocants (N = 1,148) was based on broadband spectrograms (KAY-CSL) and auditory impressions. Fundamental frequency (F0) analyses were performed (PRAAT) and the pattern of the F0 contour (melody) analysed using specific in-lab software (CDAP, pw-project). Generalized mixed linear models were used to perform group comparisons.

RESULTS

There was a clear predominance of a simple rising-falling pattern (single melody arcs) in vocants of both groups. Nonetheless, significantly more complex contours, particularly, double-arc structures, were found in vocants of the CO group. Moreover, vocants of the HI group were shorter than those uttered by the CO group, while the mean F0 did not significantly differ.

CONCLUSION

Vocants are characterized by both, innate features, found in HI and CO groups, and features that additionally require a functioning auditory system. Even at an early pre-linguistic stage, somatosensory sensations cannot compensate for a lack of auditory feedback. Vocants might be relevant in the early diagnosis of hearing disorders and assessments of the effectiveness of, or adjustments required to, hearing aids.

Age differences in binaural and working memory abilities in school-going children

OBJECTIVES

Binaural hearing is the interplay of acoustic cues (interaural time differences: ITD, interaural level differences: ILD, and spectral cues) and cognitive abilities (e.g., working memory, attention). The current study investigated the effect of developmental age on auditory binaural resolution and working memory and the association between them (if any) in school-going children.

METHODS

Fifty-seven normal-hearing school-going children aged 6-15 y were recruited for the study. The participants were divided into three groups: Group 1 (n=17, M_age = 7.1y ± 0.72 y), Group 2 (n = 23; M_age = 10.2y ± 0.8 y), Group 3 (n = 17; M_age: 14.1 y ±1.3 y). Group 4, with normal hearing young adults (n = 20; M_age = 21.1 y± 3.2 y), was included for comparing the maturational changes in former groups with adult values. Tests of binaural resolution (ITD and ILD thresholds) and auditory working memory (forward and backward digit span and 2n-back digit) were administered to all the participants.

RESULTS

Results indicated a main effect of age on spatial resolution and working memory, with the median of lower age groups (Group 1 & Group 2) being significantly poorer (p < 0.01) than the higher age groups (Group 3 & Group 4). Groups 2, 3, and 4 performed significantly better than Group 1 (p < 0.001) on the forward span and ILD task. Groups 3 and 4 had significantly better ITD (p = 0.04), backward span (p = 0.02), and 2n-back scores than Group 2. A significant correlation between scores on working memory tasks and spatial resolution thresholds was also found. On discriminant function analysis, backward span and ITD emerged as sensitive measures for segregating older groups (Group 3 & Group 4) from younger groups (Group 1 & Group 2).

CONCLUSIONS

The present study showed that the ILD thresholds and forward digit span mature by nine years. However, the backward digit span score continued to mature beyond 15 y. This finding can be attributed to the influence of auditory attention (a working memory process) on the binaural resolution, which is reported to mature till late adolescence.

The Magnitude of Contralateral Suppression of Otoacoustic Emissions Is Ear- and Age-Dependent

The maturation of the uncrossed medial olivocochlear (UMOC) efferent remains poorly documented to date. The UMOC efferent system allows listeners to not only detect but also to process, recognize, and discriminate auditory stimuli. Its fibers can be explored non-invasively by recording the effect of contralateral acoustic stimulation (CAS), resulting in a decrease in the amplitude of transient evoked otoacoustic emissions (TEOAE). The objective of the present cross-sectional study was to investigate how the effectiveness of this system varies with age in healthy subjects aged 8 years to adulthood. For this purpose, 120 right-handed native French-speaking subjects (57 females and 63 males) were divided into five age groups of 24 subjects each: 8y-10y, 10y-11y6m, 11y6m-13y, 13y-17y, and ≥18y. TEOAE amplitudes with and without CAS were recorded. The equivalent attenuation (EA) was calculated, corresponding to the change in TEOAE amplitude equivalent to the effect generated by CAS. General linear models were performed to control for the effect of ear, sex, and age on EA. No sex effect was found. A stronger EA was consistently found regardless of age group in the right ear compared to the left. In contrast to the right ear, for which, on average, EA remained constant across age groups, an increasingly weaker TEOAE suppression effect with age was found in the left ear, reinforcing the asymmetrical functioning of the UMOC efferent system in favor of the right ear in adulthood. Further studies are needed to investigate the lateralization of the UMOC efferent system and its changes over time in cases of atypical or reversed cortical asymmetries, especially in subjects with specific learning disorders.

The effect of stimulus type and testing method on talker discrimination of school-age children

Efficient talker discrimination (TD) improves speech understanding under multi-talker conditions. So far, TD of children has been assessed using various testing parameters, making it difficult to draw comparative conclusions. This study explored the effects of the stimulus type and variability on children's TD. Thirty-two children (7-10 years old) underwent eight TD assessments with fundamental frequency + formant changes using an adaptive procedure. Stimuli included consonant-vowel-consonant words or three-word sentences and were either fixed by run or by trial (changing throughout the run). Cognitive skills were also assessed. Thirty-one adults (18-35 years old) served as controls. The results showed (1) poorer TD for the fixed-by-trial than the fixed-by-run method, with both stimulus types for the adults but only with the words for the children; (2) poorer TD for the words than the sentences with the fixed-by-trial method only for the children; and (3) significant correlations between the children's age and TD. These results support a developmental trajectory in the use of perceptual anchoring for TD and in its reliance on comprehensive acoustic and linguistic information. The finding that the testing parameters may influence the top-down and bottom-up processing for TD should be considered when comparing data across studies or when planning new TD experiments.

Preterm babies treated with lengthy continuous positive airway pressure are associated with moderate auditory abnormality

AIMS

Continuous positive airway pressure (CPAP) has been used for the prevention and treatment of neonatal respiratory distress for over four decades, but it remains very poorly understood whether there is any brainstem auditory abnormality in babies treated with CPAP. We aimed to detect brainstem auditory abnormality at 34-35 weeks of corrected age in preterm babies treated with CPAP and define any difference between different durations of CPAP treatment.

STUDY DESIGN

Preterm babies were recruited and dichotomized to those with CPAP treatment (CPAP group, n = 67) and those without CPAP treatment (n-CPAP group) (n = 49). Brainstem auditory evoked response (BAER) was studied at 34-35 weeks of corrected age.

RESULTS

Compared with the n-CPAP group, the CPAP group manifested moderately elevated BAER threshold and significantly prolonged latencies of BAER waves III and V and I-V interval. The prolongation was generally more significant in the babies with longer duration of CPAP treatment than those with shorter duration. The I-V interval in the babies with CPAP treatment for >30 days were significantly longer than those with fewer days of CPAP treatment.

CONCLUSION

At 34-35 weeks of corrected age, preterm babies treated with CPAP are associated with moderate auditory abnormality. Further study is warranted to explore more detail of the auditory abnormality in babies treated with CPAP.

Auditory and Somatosensory Development for Speech in Later Childhood

PURPOSE

This study collected measures of auditory-perceptual and oral somatosensory acuity in typically developing children and adolescents aged 9-15 years. We aimed to establish reference data that can be used as a point of comparison for individuals with residual speech sound disorder (RSSD), especially for RSSD affecting American English rhotics. We examined concurrent validity between tasks and hypothesized that performance on at least some tasks would show a significant association with age, reflecting ongoing refinement of sensory function in later childhood. We also tested for an inverse relationship between performance on auditory and somatosensory tasks, which would support the hypothesis of a trade-off between sensory domains.

METHOD

Ninety-eight children completed three auditory-perceptual tasks (identification and discrimination of stimuli from a "rake"-"wake" continuum and category goodness judgment for naturally produced words containing rhotics) and three oral somatosensory tasks (bite block with auditory masking, oral stereognosis, and articulatory awareness, which involved explicit judgments of relative tongue position for different speech sounds). Pairwise associations were examined between tasks within each domain and between task performance and age. Composite measures of auditory-perceptual and somatosensory functions were used to investigate the possibility of a sensory trade-off.

RESULTS

Statistically significant associations were observed between the identification and discrimination tasks and the bite block and articulatory awareness tasks. In addition, significant associations with age were found for the category goodness and bite block tasks. There was no statistically significant evidence of a trade-off between auditory-perceptual and somatosensory domains.

CONCLUSIONS

This study provided a multidimensional characterization of speech-related sensory function in older children/adolescents. Complete materials to administer all experimental tasks have been shared, along with measures of central tendency and dispersion for scores in two subgroups of age. Ultimately, we hope to apply this information to make customized treatment recommendations for children with RSSD based on sensory profiles.

Iodine status during child development and hearing ability: a systematic review

Iodine, through the thyroid hormones, is required for the development of the auditory cortex and cochlea (the sensory organ for hearing). Deafness is a well-documented feature of endemic cretinism resulting from severe iodine deficiency. However, the range of effects of suboptimal iodine intake during auditory development on the hearing ability of children is less clear. We therefore aimed to systematically review the evidence for the association between iodine exposure (i.e. intake/status/supplementation) during development (i.e. pregnancy and/or childhood) and hearing outcomes in children. We searched PubMed and Embase and identified 330 studies, of which thirteen were included in this review. Only three of the thirteen studies were of low risk of bias or of good quality, this therefore limited our ability to draw firm conclusions. Nine of the studies (69 %) were in children (one RCT, two non-RCT interventions and six cross-sectional studies) and four (31 %) were in pregnant women (one RCT, one cohort study and two case reports). The RCT of iodine supplementation in mildly iodine-deficient pregnant women found no effect on offspring hearing thresholds. However, hearing was a secondary outcome of the trial and not all women were from an iodine-deficient area. Iodine supplementation of severely iodine-deficient children (in both non-RCT interventions) resulted in improved hearing thresholds. Five of six cross-sectional studies (83 %) found that higher iodine status in children was associated with better hearing. The current evidence base for the association between iodine status and hearing outcomes is limited and further good-quality research on this topic is needed.

Association between in vitro fertilization-embryo transfer and hearing loss: risk factors for hearing loss among twin infants in a cohort study

Assisted reproductive technologies (ART), including in vitro fertilization-embryo transfer (IVF-ET) and intracytoplasmic sperm injection (ICSI), are known to contribute a higher risk of birth defects; however, studies have rarely evaluated the association between IVF-ET and diagnostic hearing loss (HL). This study aimed to evaluate the prevalence of and risk factors for HL and to clarify the association between IVF-ET and HL among twinborn infants. We enrolled 1860 live-born twin neonates born at a hospital in China from January 2017 to December 2020. After multi-step hearing screening, participants were diagnosed with HL by pediatric audiologists at 6 months of age. The prevalence of hearing loss and the adjusted odds ratios (AORs) for specific risk factors were estimated using generalized estimation equation (GEE) models in twin-born infants. Characteristics and prevalence of failure for hearing screening and HL were measured in IVF-ET twin infants. IVF-ET conception and preterm birth conferred a higher risk of hearing loss, with increased adjusted odds ratios (AOR [95% confidence intervals (CI)] IVF-ET: 2.82 [1.17-6.80], P = 0.021; preterm birth: 6.14 [2.30-16.40], P < 0.001) than the control group, respectively. Among the 1860 twin infants, more IVF-ET twins failed in dual-step hearing screening (3.26%) and were diagnosed with hearing loss (2.21%) than those conceived by spontaneous pregnancy.

CONCLUSION

IVF-ET conception and premature birth were associated with a higher risk of hearing impairment. Twin infants conceived by IVF-ET tended to fail in hearing screening and be diagnosed with hearing loss. These observations provide a more comprehensive approach for the prevention and management of deafness in twin-born children.

WHAT IS KNOWN

• IVF-ET technologies conferred a higher risk of birth defects.

WHAT IS NEW

• Premature birth and IVF-ET conception were associated with a higher risk of hearing loss among twin infants. • Twin infants conceived by IVF-ET tended to fail in hearing screening and diagnosed with hearing loss.

Development of categorical speech perception in Mandarin-speaking children and adolescents

Although children develop categorical speech perception at a very young age, the maturation process remains unclear. A cross-sectional study in Mandarin-speaking 4-, 6-, and 10-year-old children, 14-year-old adolescents, and adults (n = 104, 56 males, all Asians from mainland China) was conducted to investigate the development of categorical perception of four Mandarin phonemic contrasts: lexical tone contrast Tone 1-2, vowel contrast /u/-/i/, consonant aspiration contrast /p/-/p^h /, and consonant formant transition contrast /p/-/t/. The results indicated that different types of phonemic contrasts, and even the identification and discrimination of the same phonemic contrast, matured asynchronously. The observation that tone and vowel perception are achieved earlier than consonant perception supports the phonological saliency hypothesis.

A 3-Year Follow-Up and Radiological Analysis of Cochlear Implantation Patients with Cochlear Nerve Deficiency and Modiolar Deficiency-Type Malformations

OBJECTIVE

Cochlear nerve deficiency (CND) is often combined with modiolar deficiency-type inner ear malformations, which cause variable cochlear implantation (CI) outcomes. We aimed to assess the postoperative development of auditory and speech perception in CND patients with modiolar deficiency-type malformations after 3 years of follow-up to determine the factors correlated with CI outcomes.

METHODS

Sixty-seven CND patients with modiolar deficiency-type malformations who underwent CI surgery were retrospectively reviewed. Modiolar deficiency-type malformations included common cavity (CC), cochlear hypoplasia (CH) (including CH-I and CH-II) and incomplete partition-I (IP-I). Categorical auditory performance (CAP) and the infant-toddler meaningful auditory integration scale (MAIS) were used to assess auditory ability. The speech intelligibility rating (SIR) and meaningful use of speech scale (MUSS) were used to assess the speech intelligibility of these CI patients. The CI outcomes were evaluated at 0, 12, 24 and 36 months after implant activation.

RESULTS

All patients demonstrated improvements in auditory ability and speech intelligibility after CI. There were no significant differences in CI outcomes at any time point according to the malformation type. The number of nerve bundles within the internal auditory canal (IAC) showed significant differences at 12, 24 and 36 months after CI ( p < 0.05). Patients with one nerve bundle had relatively poor CI outcomes.

CONCLUSIONS

CND patients with modiolar deficiency-type malformations showed continuous improvement in auditory and speech abilities after CI. Compared with malformations, the number of nerve bundles should be given more attention when selecting the side for CI.

Pre-attentive fundamental frequency processing in Mandarin-speaking children with cochlear implants as revealed by the peak latency of positive mismatch response

Introduction

Fundamental frequency (F0) serves as the primary acoustic cue for Mandarin tone perception. Recent behavioral studies suggest that F0 information may be differently processed between Mandarin-speaking normal-hearing (NH) children and children with cochlear implants (CIs), which may partially explain the unsatisfactory outcome of lexical tone recognition using CIs with tonal language-oriented speech processing strategies. The aim of the current study was to provide neural evidence of F0 processing in Mandarin-speaking kindergarten-aged children with CIs compared with NH children.

Methods

Positive mismatch responses (p-MMRs) to the change of the two acoustic dimensions of F0 (F0 contour and F0 level) in Mandarin-speaking kindergarten-aged children with CIs (n = 19) and their age-matched NH peers (n = 21).

Results

The two groups of children did not show any significant difference on the mean amplitude of p-MMR to either F0 contour or F0 level change. While the CI group exhibited a significantly shorter peak latency of p-MMR to F0 contour change than to F0 level change, an opposite pattern was observed in the NH group.

Discussion

This study revealed a higher sensitivity to F0 contour change than to F0 level change in children with CIs, which was different from that in NH children. The neural evidence of discrepant F0 processing between children with CIs and NH children in this study was consistent with the previously reported behavioral findings and may serve as a reference for the development and improvement of tonal language-oriented speech processing strategies.

Effects of Unilateral Hearing Loss on Speech-Evoked Auditory Brainstem Responses and Reading: A Preliminary Study

Purpose:

The purpose of this study was to determine whether the speech-evoked auditory brainstem responses (sABRs) obtained by stimulating the ear with normal sensitivity in children with unilateral hearing loss (UHL) were different from that of children with normal hearing (NH), and to explore correlations between the sABR findings and measures of reading.

Method:

Eleven children with UHL and 11 children with NH were tested via the BioMARK sABR protocol using the syllable /da/; latency and amplitudes of Waves V, A, C, D, E, F, and O were measured. Participants also were tested on the Phonemic Synthesis Test (PST) and the Woodcock Reading Mastery Test–Revised (WRMT-R), particularly the Reading Readiness, Basic Skills, and Comprehension subtests.

Results:

Multivariate analysis of variance testing showed a significantly higher amplitude for Wave A for the NH group as compared to the UHL group. Separate ANOVAs also found significantly lower scores for the UHL group compared to the NH group on Basic Skills and Comprehension subtests of the Woodcock. Significant positive Spearman rho correlations were found for the UHL group between wave amplitudes for V, A, and O and the Reading Readiness score, and between wave amplitudes for V, A, D, and O and the Reading Comprehension score. A significant correlation also was found between the Total Reading score and wave amplitudes for V and A. No such correlations were found between wave amplitude and Woodcock scores for the NH group. Further testing of the UHL data found significant relationships between the pure-tone average of the hearing loss ear and the Basic Skills, Comprehension, and Total Reading scores from the WRMT-R. There was also a significant correlation between the PST score and Wave C amplitude.

Conclusion:

There may be a connection between speech encoding and measures of reading in children with UHL.

Speech-Evoked Envelope Following Responses in Children and Adults

PURPOSE

Envelope following responses (EFRs) could be useful for objectively evaluating audibility of speech in children who are unable to participate in routine clinical tests. However, relative to adults, the characteristics of EFRs elicited by frequency-specific speech and their utility in predicting audibility in children are unknown.

METHOD

EFRs were elicited by the first (F1) and second and higher formants (F2+) of male-spoken vowels /u/ and /i/ and by fricatives /ʃ/ and /s/ in the token /suʃi/ presented at 15, 35, 55, 65, and 75 dB SPL. The F1, F2+, and fricatives were low-, mid-, and high-frequency dominant, respectively. EFRs were recorded between the vertex and the nape from twenty-three 6- to 17-year-old children and 21 young adults with normal hearing. Sensation levels of stimuli were estimated based on behavioral thresholds.

RESULTS

In children, amplitude decreased with age for /ʃ/-elicited EFRs but remained stable for low- and mid-frequency stimuli. As a group, EFR amplitude and phase coherence did not differ from that of adults. EFR sensitivity (proportion of audible stimuli detected) and specificity (proportion of inaudible stimuli not detected) did not vary between children and adults. Consistent with previous work, EFR sensitivity increased with stimulus frequency and level. The type of statistical indicator used for EFR detection did not influence accuracy in children.

CONCLUSIONS

Adultlike EFRs in 6- to 17-year-old typically developing children suggest mature envelope encoding for low- and mid-frequency stimuli. EFR sensitivity and specificity in children, when considering a wide range of stimulus levels and audibility, are ~77% and ~92%, respectively.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21136171.

The effect of child development on the components of the Frequency Following Response: Child development and the Frequency Following Response

During childhood, neuronal modifications occur so that typical childhood communicative development occurs. This work aims to contribute to the understanding of differences in the speech encoding of infants and school-age children by assessing the effects of child development, in different phases of early childhood, on the encoding of speech sounds. There were 98 subjects of both sexes, aged from 1 day to 8 years and 9 months who participated in the study. All subjects underwent a Frequency Following Response (FFR) assessment. A regression and linear correlation showed the effects of age in the FFR components, i.e., significant decrease in the latency and increased amplitude of all FFR waves with age. An increase in the slope measure was also observed. Younger infants require more time and show less robust responses when encoding speech than their older counterparts, which were shown to have more stable and well-organized FFR responses.

Evaluation and Nonsurgical Treatment of Neonatal Ear Anomalies: A Case Report

BACKGROUND

Inspection and evaluation of the neonate's ears are important parts of the neonatal examination. Neonates display a wide variety of ear size and configuration. In many cases, ear molding techniques obviate the need for future surgical correction. This article provides a review of the fetal ear development and describes common physical examination findings of the newborn's external ear. A case report reviews a successful nonsurgical treatment of a minor ear deformity.

CLINICAL FINDINGS

Newborn infant with near absent to very thin bilateral helical rims and otherwise normal bilateral ear shape and structures.

PRIMARY DIAGNOSIS

Bilateral Stahl's ear deformity.

INTERVENTIONS

The EarBuddies product was applied to bilateral ears in an outpatient pediatric plastic surgery clinic. This product remained in place for 8 weeks.

OUTCOMES

The family was pleased with the overall progress and shape of their child's ears. At 18 months of age, the family has no desire to pursue surgical correction of their child's ears.

PRACTICE RECOMMENDATIONS

Assessment of the newborn's external ear is part of a routine admission examination. Careful attention to abnormal or unusual findings allows for prompt evaluation and nonsurgical intervention.

Effect of the prenatal electromagnetic field exposure on cochlear nucleus neurons and oligodendrocytes in rats

Electromagnetic radiation from elecromagnetic field (EMF) sources has been an important health concern for a long time. The vast majority of this exposure is due to the widespread use of mobile phones, an important source of the EMF. The EMF generated by mobile phones may have adverse effects on the various biological structures that regulate the body system and function. In this study, it was aimed to evaluate histopathologically the effects of 900-megahertz (MHz) EMF application in the prenatal period on the development of the ventral cochlear nucleus, which is the first place of hearing in the brainstem, at various time points of the postnatal period in rats. In the study, Sprague-Dawley pregnant rats were divided randomly into two groups as the control group and the EMF group. The rats in the EMF group were exposed to a 900-MHz EMF every day until birth, while no EMF was applied to the rats in the control group. Auditory brainstem responses of both groups were recorded on the postnatal 13th day, the day the hearing starts. Newborn rats were sacrificed by anesthesia on days 7, 10, 15, and 30. Contrary to the control group, structural damage in cochlear nuclear neurons and oligodendrocyte cell structures and increased caspase-3 activity were observed in the postnatal period in the EMF groups. However, no significant difference was observed between the groups in terms of structural damage and caspase-3 activity at different stages of the postnatal period when cochlear nucleus development was observed. According to ABS, there was no significant difference between the average latency of waves in both groups. In conclusion, this study shows that 900-MHz electromagnetic waves propagated from mobile phones during the prenatal period have no harmful effects on the development of the ventral cochlear nucleus of rats.

Trajectories of receptive and expressive vocabulary in Mandarin speaking children under 4 years of age fitted with cochlear implants: a 12-month longitudinal study

OBJECTIVE

To explore trajectories of receptive and expressive vocabulary in Mandarin-speaking children under the age of 4 years, fitted with cochlear implants (CIs).

DESIGN

Vocabulary trajectories were measured at baseline, 3, 6, and 12 months after implantation using the Chinese version of the MacArthur-Bates Communicative Development Inventory.

STUDY SAMPLE

There were 216 children with CIs in West China Hospital who took part and were divided into three groups based on age at first CI.

RESULTS

Receptive and expressive vocabulary scores of the younger implantation group were significantly different from the older groups at baseline. After 12 months of implant use, there were no significant differences between all groups. Furthermore receptive vocabulary trajectories for all children with CIs were not significantly different from those of children with normal hearing. However, expressive vocabulary trajectories were poorer when compared to children with normal hearing. Significant differences were seen between receptive and expressive vocabulary in all age groups.

CONCLUSIONS

This study suggests no differences in vocabulary trajectories in Mandarin-speaking children whether they received their first CI at 1, 2, or 3 years of age. It is important that clinicians convey realistic expectations about potential differences in receptive vs. expressive trajectories for Mandarin-speaking children fitted with CIs.

Relevance to the higher order structure may govern auditory statistical learning in neonates

Hearing is one of the earliest senses to develop and is quite mature by birth. Contemporary theories assume that regularities in sound are exploited by the brain to create internal models of the environment. Through statistical learning, internal models extrapolate from patterns to predictions about subsequent experience. In adults, altered brain responses to sound enable us to infer the existence and properties of these models. In this study, brain potentials were used to determine whether newborns exhibit context-dependent modulations of a brain response that can be used to infer the existence and properties of internal models. Results are indicative of significant context-dependence in the responsivity to sound in newborns. When common and rare sounds continue in stable probabilities over a very long period, neonates respond to all sounds equivalently (no differentiation). However, when the same common and rare sounds at the same probabilities alternate over time, the neonate responses show clear differentiations. The context-dependence is consistent with the possibility that the neonate brain produces more precise internal models that discriminate between contexts when there is an emergent structure to be discovered but appears to adopt broader models when discrimination delivers little or no additional information about the environment.

Spectral Resolution Development in Children With Normal Hearing and With Cochlear Implants: A Review of Behavioral Studies

PURPOSE

This review article provides a theoretical overview of the development of spectral resolution in children with normal hearing (cNH) and in those who use cochlear implants (CIs), with an emphasis on methodological considerations. The aim was to identify key directions for future research on spectral resolution development in children with CIs.

METHOD

A comprehensive literature review was conducted to summarize and synthesize previously published behavioral research on spectral resolution development in normal and impaired auditory systems.

CONCLUSIONS

In cNH, performance on spectral resolution tasks continues to improve through the teenage years and is likely driven by gradual maturation of across-channel intensity resolution. A small but growing body of evidence from children with CIs suggests a more complex relationship between spectral resolution development, patient demographics, and the quality of the CI electrode-neuron interface. Future research should aim to distinguish between the effects of patient-specific variables and the underlying physiology on spectral resolution abilities in children of all ages who are hard of hearing and use auditory prostheses.

Congenital Sensorineural Hearing Loss

Congenital sensorineural hearing loss is highly prevalent in our population, with a wide variety of causes. The key to clinical management is early detection and intervention, to promote language and cognitive development. With expanding genetic knowledge about congenital sensorineural hearing loss, the indiscriminate approach in workup is no longer recommended. Comprehensive genetic evaluation and cytomegalovirus testing are key to identify the underlying cause of the hearing loss. Treatment and prognosis depend on age of hearing loss onset and detection; management plans will typically include audiology consultation, speech therapy, and various hearing amplification devices and technologies when applicable.