Infants' neural speech discrimination predicts individual differences in grammar ability at 6 years of age and their risk of developing speech-language disorders

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.

Socioeconomic status (SES) and cognitive outcomes are predicted by resting-state EEG in school-aged children

Children's socioeconomic status (SES) is related to patterns of intrinsic resting-state brain function that subserve relevant cognitive processes over the course of development. Although infant research has demonstrated the association between children's environments, cognitive outcomes, and resting-state electroencephalography (rsEEG), it remains unknown how these aspects of their environment, tied to SES, impact neural and cognitive development throughout the school years. To address this gap, we applied a multivariate pattern analysis (MVPA) to rsEEG data to identify which neural frequencies at rest are differentially associated with unique aspects of socioeconomic status (SES; income and maternal education) and cognitive (vocabulary, working memory) outcomes among school-aged children (8-15 years). We find that the alpha frequency is associated with both income and maternal education, while lower gamma and theta fluctuations are tied to dissociable aspects of SES and cognitive outcomes. Specifically, changes in the gamma frequency are predictive of both maternal education and vocabulary outcome, while changes in the theta frequency are related to both income and working memory ability. The current findings extend our understanding of unique pathways by which SES influences cognitive and neural development in school-aged children.

Phonetic perceptual reorganization across the first year of life: Looking back

This paper provides a selective overview of some of the research that has followed from the publication of Werker and Tees (1984a) "Cross-language speech perception: Evidence for Perceptual Reorganization During the First Year of Life." Specifically, I briefly present the original finding, our interpretation of its meaning, and some key replications and extensions. I then review some of the work that has followed, including work with different kinds of populations, different kinds of speech sound contrasts, as well as attunement (perceptual reorganization) to additional properties of language beyond phonetic contrasts. Included is the body of work that queries whether perceptual attunement is a critical period phenomenon. Potential learning mechanisms for how experience functions to guide phonetic perceptual development are also presented, as is work on the relation between speech perception and word learning.

Social Brain Perspectives on the Social and Evolutionary Neuroscience of Human Language

Human language and social cognition are two key disciplines that have traditionally been studied as separate domains. Nonetheless, an emerging view suggests an alternative perspective. Drawing on the theoretical underpinnings of the social brain hypothesis (thesis of the evolution of brain size and intelligence), the social complexity hypothesis (thesis of the evolution of communication), and empirical research from comparative animal behavior, human social behavior, language acquisition in children, social cognitive neuroscience, and the cognitive neuroscience of language, it is argued that social cognition and language are two significantly interconnected capacities of the human species. Here, evidence in support of this view reviews (1) recent developmental studies on language learning in infants and young children, pointing to the important crucial benefits associated with social stimulation for youngsters, including the quality and quantity of incoming linguistic information, dyadic infant/child-to-parent non-verbal and verbal interactions, and other important social cues integral for facilitating language learning and social bonding; (2) studies of the adult human brain, suggesting a high degree of specialization for sociolinguistic information processing, memory retrieval, and comprehension, suggesting that the function of these neural areas may connect social cognition with language and social bonding; (3) developmental deficits in language and social cognition, including autism spectrum disorder (ASD), illustrating a unique developmental profile, further linking language, social cognition, and social bonding; and (4) neural biomarkers that may help to identify early developmental disorders of language and social cognition. In effect, the social brain and social complexity hypotheses may jointly help to describe how neurotypical children and adults acquire language, why autistic children and adults exhibit simultaneous deficits in language and social cognition, and why nonhuman primates and other organisms with significant computational capacities cannot learn language. But perhaps most critically, the following article argues that this and related research will allow scientists to generate a holistic profile and deeper understanding of the healthy adult social brain while developing more innovative and effective diagnoses, prognoses, and treatments for maladies and deficits also associated with the social brain.

Verbal, Figural, and Arithmetic Fluency of Children with Cochlear Implants

Cochlear implantation gives children with prelingual severe hearing loss and deafness the opportunity to develop their hearing abilities, speech, language, cognitive abilities and academic skills with adequate rehabilitation. The aim of the research was to analyze verbal, figural and arithmetic fluency and their interrelationship in children with a cochlear implant (CI) and children with normal hearing (NH). A total of 46 children with CI and 110 children with NH, aged 9 to 16, participated in the research. Verbal fluency was assessed using phonemic and semantic fluency, and non-verbal fluency using figural fluency. Arithmetic fluency was assessed using simple arithmetic tasks within the number range up to 100. The results showed that children with CI achieved poorer results in phonemic fluency (z = -4.92; p < 0.001), semantic fluency (z = -3.89; p < 0.001), figural fluency (z = -3.07; p = 0.002), and arithmetic fluency (z = -4.27; p < 0.001). In both groups, a positive correlation was obtained between the measured modalities and types of fluency. In the group of children with CI, a sex difference was obtained on the phonemic fluency test, in favor of girls. The age of children with CI was correlated with arithmetic fluency. Verbal, figural and arithmetic fluency of children with CI speak in favor of the importance of early auditory and language experiences.

Technologies to support the diagnosis and/or treatment of neurodevelopmental disorders: A systematic review

In recent years, there has been a great interest in utilizing technology in mental health research. The rapid technological development has encouraged researchers to apply technology as a part of a diagnostic process or treatment of Neurodevelopmental Disorders (NDDs). With the large number of studies being published comes an urgent need to inform clinicians and researchers about the latest advances in this field. Here, we methodically explore and summarize findings from studies published between August 2019 and February 2022. A search strategy led to the identification of 4108 records from PubMed and APA PsycInfo databases. 221 quantitative studies were included, covering a wide range of technologies used for diagnosis and/or treatment of NDDs, with the biggest focus on Autism Spectrum Disorder (ASD). The most popular technologies included machine learning, functional magnetic resonance imaging, electroencephalogram, magnetic resonance imaging, and neurofeedback. The results of the review indicate that technology-based diagnosis and intervention for NDD population is promising. However, given a high risk of bias of many studies, more high-quality research is needed.

Implementation of an Early Communication Intervention for Young Children with Cerebral Palsy Using Single-Subject Research Design

The implementation of an intervention protocol aimed at increasing vocal complexity in three pre-linguistic children with cerebral palsy (two males, starting age 15 months, and one female, starting age 16 months) was evaluated utilising a repeated ABA case series design. The study progressed until the children were 36 months of age. Weekly probes with trained and untrained items were administered across each of three intervention blocks. Successive blocks targeted more advanced protophone production and speech movement patterns, individualised for each participant. Positive treatment effects were seen for all participants in terms of a greater rate of achievement of target protophone categories and speech movement patterns. Tau coefficients for trained items demonstrated overall moderate to large AB phase contrast effect sizes, with limited evidence of generalisation to untrained items. Control items featuring protophones and speech movements not targeted for intervention showed no change across phases for any participant. Our data suggest that emerging speech-production skills in prelinguistic infants with CP can be positively influenced through a multimodal intervention focused on capitalising on early periods of plasticity when language learning is most sensitive.

The emergence of bifurcated structure in children's language

Human language is unique among animal communication systems, in part because of its dual patterning in which meaningless phonological units combine to form meaningful words (phonological structure) and words combine to form sentences (lexicosyntactic structure). Although dual patterning is well recognized, its emergence in language development has been scarcely investigated. Chief among questions still unanswered is the extent to which development of these separate structures is independent or interdependent, and what supports acquisition of each level of structure. We explored these questions by examining growth of lexicosyntactic and phonological structure in children with normal hearing (n = 49) and children with hearing loss who use cochlear implants (n = 56). Multiple measures of each kind of structure were collected at 2-year intervals (kindergarten through eighth grade), and used to construct latent scores for each type of structure. Growth curve analysis assessed (a) the relative independence of development for each level of structure; (b) interactions between these two levels of structure in real-time language processing; and (c) contributions to growth of each level of structure made by auditory input, socioeconomic status (as proxy for linguistic experience), and speech motor control. Findings suggested that phonological and lexicosyntactic structure develop largely independently. Auditory input, socioeconomic status, and speech motor control help shape these language structures, with the last two factors exerting stronger effects for children with cochlear implants. Only for children with cochlear implants were interdependencies in real-time processing observed, reflecting compensatory mechanisms likely present to help them handle the disproportionately large phonological deficit they exhibit. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Brain myelination at 7 months of age predicts later language development

Between 6 and 12 months of age there are dramatic changes in infants' processing of language. The neurostructural underpinnings of these changes are virtually unknown. The objectives of this study were to (1) examine changes in brain myelination during this developmental period and (2) examine the relationship between myelination during this period and later language development. Macromolecular proton fraction (MPF) was used as a marker of myelination. Whole-brain MPF maps were obtained with 1.25 mm3 isotropic spatial resolution from typically developing children at 7 and 11 months of age. Effective myelin density was calculated from MPF based on a linear relationship known from the literature. Voxel-based analyses were used to identify longitudinal changes in myelin density and to calculate correlations between myelin density at these ages and later language development. Increases in myelin density were more predominant in white matter than in gray matter. A strong predictive relationship was found between myelin density at 7 months of age, language production at 24 and 30 months of age, and rate of language growth. No relationships were found between myelin density at 11 months, or change in myelin density between 7 and 11 months of age, and later language measures. Our findings suggest that critical changes in brain structure may precede periods of pronounced change in early language skills.

Development of executive function-relevant skills is related to both neural structure and function in infants

The development of skills related to executive function (EF) in infancy, including their emergence, underlying neural mechanisms, and interconnections to other cognitive skills, is an area of increasing research interest. Here, we report on findings from a multidimensional dataset demonstrating that infants' behavioral performance on a flexible learning task improved across development and that the task performance is highly correlated with both neural structure and neural function. The flexible learning task probed infants' ability to learn two different associations, concurrently, over 16 trials, requiring multiple skills relevant to EF. We examined infants' neural structure by measuring myelin density in the brain, using a novel macromolecular proton fraction (MPF) mapping method. We further examined an important neural function of speech processing by characterizing the mismatch response (MMR) to speech contrasts using magnetoencephalography (MEG). All measurements were performed longitudinally in monolingual English-learning infants at 7- and 11-months of age. At the group level, 11-month-olds, but not 7-month-olds, demonstrated evidence of learning both associations in the behavioral task. Myelin density in the prefrontal region at 7 months of age was found to be highly predictive of behavioral task performance at 11 months of age, suggesting that myelination may support the development of these skills. Furthermore, a machine-learning regression analysis revealed that individual differences in the behavioral task are predicted by concurrent neural speech processing at both ages, suggesting that these skills do not develop in isolation. Together, these cross-modality results revealed novel insights into EF-related skills. HIGHLIGHT: Monolingual infants demonstrated flexible learning on a task requiring executive function skills at 11 months, but not at 7 months. Infants' myelin density at 7 months is highly predictive of their behavioral performance in the flexible learning task at 11 months of age. Individual differences in the flexible learning task performance are also correlated with concurrent neural processing of speech at both ages.

Development of infants' neural speech processing and its relation to later language skills: A MEG study

The 'sensitive period' for phonetic learning (∼6-12 months) is one of the earliest milestones in language acquisition where infants start to become specialized in processing speech sounds in their native language. In the last decade, advancements in neuroimaging technologies for infants are starting to shed light on the underlying neural mechanisms supporting this important learning period. The current study reports on a large longitudinal dataset with the aim to replicate and extend on two important questions: 1) what are the developmental changes during the 'sensitive period' for native and nonnative speech processing? 2) how does native and nonnative speech processing in infants predict later language outcomes? Fifty-four infants were recruited at 7 months of age and their neural processing of speech was measured using Magnetoencephalography (MEG). Specifically, the neural sensitivity to a native and a nonnative speech contrast was indexed by the mismatch response (MMR). They repeated the measurement again at 11 months of age and their language development was further tracked from 12 months to 30 months of age using the MacArthur-Bates Communicative Development Inventory (CDI). Using an a priori Region-of-Interest (ROI) approach, we observed significant increases for the Native MMR in the left inferior frontal region (IF) and superior temporal region (ST) from 7 to 11 months, but not for the Nonnative MMR. Complementary whole brain comparison revealed more widespread developmental changes for both contrasts. However, only individual differences in the left IF and ST for the Nonnative MMR at 11 months of age were significant predictors of individual vocabulary growth up to 30 months of age. An exploratory machine-learning based analysis further revealed that whole brain time series for both Native and Nonnative contrasts can robustly predict later outcomes, but with very different underlying spatial-temporal patterns. The current study extends our current knowledge and suggests that native and nonnative speech processing may follow different developmental trajectories and utilize different mechanisms that are relevant for later language skills.

Language experience during the sensitive period narrows infants' sensory encoding of lexical tones-Music intervention reverses it

The sensitive period for phonetic learning (6∼12 months), evidenced by improved native speech processing and declined non-native speech processing, represents an early milestone in language acquisition. We examined the extent that sensory encoding of speech is altered by experience during this period by testing two hypotheses: (1) early sensory encoding of non-native speech declines as infants gain native-language experience, and (2) music intervention reverses this decline. We longitudinally measured the frequency-following response (FFR), a robust indicator of early sensory encoding along the auditory pathway, to a Mandarin lexical tone in 7- and 11-months-old monolingual English-learning infants. Infants received either no intervention (language-experience group) or music intervention (music-intervention group) randomly between FFR recordings. The language-experience group exhibited the expected decline in FFR pitch-tracking accuracy to the Mandarin tone, while the music-intervention group did not. Our results support both hypotheses and demonstrate that both language and music experiences alter infants' speech encoding.

Rapid learning of a phonemic discrimination in the first hours of life

Human neonates can discriminate phonemes, but the neural mechanism underlying this ability is poorly understood. Here we show that the neonatal brain can learn to discriminate natural vowels from backward vowels, a contrast unlikely to have been learnt in the womb. Using functional near-infrared spectroscopy, we examined the neuroplastic changes caused by 5 h of postnatal exposure to random sequences of natural and reversed (backward) vowels (T1), and again 2 h later (T2). Neonates in the experimental group were trained with the same stimuli as those used at T1 and T2. Compared with controls, infants in the experimental group showed shorter haemodynamic response latencies for forward vs backward vowels at T1, maximally over the inferior frontal region. At T2, neural activity differentially increased, maximally over superior temporal regions and the left inferior parietal region. Neonates thus exhibit ultra-fast tuning to natural phonemes in the first hours after birth.

Early temperament as a predictor of language skills at 40 months

Background

Mastering language involves the development of expressive and receptive skills among children. While it has been speculated that early temperament plays a role in the acquisition of language, the actual mechanism has not yet been explored. We investigated whether temperament at 18 months predicted expressive or receptive language skills at 40 months.

Methods

A representative sample of 901 children and their mothers who were enrolled and followed-up longitudinally in the Hamamatsu Birth Cohort for Mothers and Children study was included in the analysis. Child temperament was measured at 18 months using the Japanese version of the Early Childhood Behavior Questionnaire. Expressive and receptive language skills were measured at 40 months using the Mullen Scales of Early Learning.

Results

The multiple regression analysis, adjusting for potential confounders, suggested that higher motor activation (fidgeting) at 18 months was associated with lower expressive and receptive language skills at 40 months. Higher perceptual sensitivity was associated with higher expressive and receptive language skills at 40 months.

Conclusions

Specific temperament at 18 months of age predicted the development of the child’s expressive and receptive language skills at 40 months.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03116-5.

Towards a model of language neurobiology in early development

Understanding language neurobiology in early childhood is essential for characterizing the developmental structural and functional changes that lead to the mature adult language network. In the last two decades, the field of language neurodevelopment has received increasing attention, particularly given the rapid advances in the implementation of neuroimaging techniques and analytic approaches that allow detailed investigations into the developing brain across a variety of cognitive domains. These methodological and analytical advances hold the promise of developing early markers of language outcomes that allow diagnosis and clinical interventions at the earliest stages of development. Here, we argue that findings in language neurobiology need to be integrated within an approach that captures the dynamic nature and inherent variability that characterizes the developing brain and the interplay between behavior and (structural and functional) neural patterns. Accordingly, we describe a framework for understanding language neurobiology in early development, which minimally requires an explicit characterization of the following core domains: i) computations underlying language learning mechanisms, ii) developmental patterns of change across neural and behavioral measures, iii) environmental variables that reinforce language learning (e.g., the social context), and iv) brain maturational constraints for optimal neural plasticity, which determine the infant's sensitivity to learning from the environment. We discuss each of these domains in the context of recent behavioral and neuroimaging findings and consider the need for quantitatively modeling two main sources of variation: individual differences or trait-like patterns of variation and within-subject differences or state-like patterns of variation. The goal is to enable models that allow prediction of language outcomes from neural measures that take into account these two types of variation. Finally, we examine how future methodological approaches would benefit from the inclusion of more ecologically valid paradigms that complement and allow generalization of traditional controlled laboratory methods.