Altered lateralization of dorsal language tracts in 6‐week‐old infants at risk for autism

Altered structural connectivity has been identified as a possible biomarker of autism spectrum disorder (ASD) risk in the developing brain. Core features of ASD include impaired social communication and early language delay. Thus, examining white matter tracts associated with language may lend further insight into early signs of ASD risk and the mechanisms that underlie language impairments associated with the disorder. Evidence of altered structural connectivity has previously been detected in 6‐month‐old infants at high familial risk for developing ASD. However, as language processing begins in utero, differences in structural connectivity between language regions may be present in the early infant brain shortly after birth. Here we investigated key white matter pathways of the dorsal language network in 6‐week‐old infants at high (HR) and low (LR) risk for ASD to identify atypicalities in structural connectivity that may predict altered developmental trajectories prior to overt language delays and the onset of ASD symptomatology. Compared to HR infants, LR infants showed higher fractional anisotropy (FA) in the left superior longitudinal fasciculus (SLF); in contrast, in the right SLF, HR infants showed higher FA than LR infants. Additionally, HR infants showed more rightward lateralization of the SLF. Across both groups, measures of FA and lateralization of these pathways at 6 weeks of age were related to later language development at 18 months of age as well as ASD symptomatology at 36 months of age. These findings indicate that early differences in the structure of language pathways may provide an early predictor of future language development and ASD risk.     

Frontolimbic neural circuitry at 6 months predicts individual differences in joint attention at 9 months

Elucidating the neural basis of joint attention in infancy promises to yield important insights into the development of language and social cognition, and directly informs developmental models of autism. We describe a new method for evaluating responding to joint attention performance in infancy that highlights the 9‐ to 10‐month period as a time interval of maximal individual differences. We then demonstrate that fractional anisotropy in the right uncinate fasciculus, a white matter fiber bundle connecting the amygdala to the ventral‐medial prefrontal cortex and anterior temporal pole, measured in 6‐month‐olds predicts individual differences in responding to joint attention at 9 months of age. The white matter microstructure of the right uncinate was not related to receptive language ability at 9 months. These findings suggest that the development of core nonverbal social communication skills in infancy is largely supported by preceding developments within right lateralized frontotemporal brain systems.     

EEG coherence,joint attention and language development in the second year

Recent research has raised the hypothesis that brain maturation processes may play an important role in the linkage between infant joint attention and language development. This hypothesis was examined using EEG, joint attention and parent report language measures in a longitudinal study of 29 infants assessed at 14, 18 and 24 months of age. The results indicated that both measures of joint attention and EEG coherence at 14 months were related to language development at 24 months. Furthermore, both EEG coherence measures and joint attention measures made contributions to multiple regression equations predicting individual differences in language development. Finally, coherence data from this study were consistent with Thatcher's (1994 ) theory of different patterns of neural integration and differentiation in the early maturation of the left and right hemispheres. The implications of these results for understanding the nature of the relations between joint attention and language development, as well as the utility of EEG coherence measures in developmental neuroscience are discussed.     

Quantifying latent social motivation and its associations with joint attention and language in infants at high and low likelihood for autism spectrum disorder

Social motivation—the psychobiological predisposition for social orienting, seeking social contact, and maintaining social interaction—manifests in early infancy and is hypothesized to be foundational for social communication development in typical and atypical populations. However, the lack of infant social-motivation measures has hindered delineation of associations between infant social motivation, other early-arising social abilities such as joint attention, and language outcomes. To investigate how infant social motivation contributes to joint attention and language, this study utilizes a mixed longitudinal sample of 741 infants at high (HL = 515) and low (LL = 226) likelihood for ASD. Using moderated nonlinear factor analysis (MNLFA), we incorporated items from parent-report measures to establish a novel latent factor model of infant social motivation that exhibits measurement invariance by age, sex, and familial ASD likelihood. We then examined developmental associations between 6- and 12-month social motivation, joint attention at 12–15 months, and language at 24 months of age. On average, greater social-motivation growth from 6–12 months was associated with greater initiating joint attention (IJA) and trend-level increases in sophistication of responding to joint attention (RJA). IJA and RJA were both positively associated with 24-month language abilities. There were no additional associations between social motivation and future language in our path model. These findings substantiate a novel, theoretically driven approach to modeling social motivation and suggest a developmental cascade through which social motivation impacts other foundational skills. These findings have implications for the timing and nature of intervention targets to support social communication development in infancy.

Highlights

• We describe a novel, theoretically based model of infant social motivation wherein multiple parent-reported indicators contribute to a unitary latent social-motivation factor.
• Analyses revealed social-motivation factor scores exhibited measurement invariance for a longitudinal sample of infants at high and low familial ASD likelihood.
• Social-motivation growth from ages 6–12 months is associated with better 12−15-month joint attention abilities, which in turn are associated with greater 24-month language skills.
• Findings inform timing and targets of potential interventions to support healthy social communication in the first year of life.

     

Habituation and novelty detection fNIRS brain responses in 5‐ and 8‐month‐old infants: The Gambia and UK

The first 1,000 days of life are a critical window of vulnerability to exposure to socioeconomic and health challenges (i.e. poverty/undernutrition). The Brain Imaging for Global Health (BRIGHT) project has been established to deliver longitudinal measures of brain development from 0 to 24 months in UK and Gambian infants and to assess the impact of early adversity. Here results from the Habituation‐Novelty Detection (HaND) functional near‐infrared spectroscopy (fNIRS) task at 5 and 8 months are presented (N = 62 UK; N = 115 Gambia). In the UK cohort distinct patterns of habituation and recovery of response to novelty are seen, becoming more robust from 5 to 8 months of age. In The Gambia, an attenuated habituation response is evident: a larger number of trials are required before the response sufficiently suppresses relative to the response during the first presented trials. Furthermore, recovery of response to novelty is not evident at 5 or 8 months of age. As this longitudinal study continues in The Gambia, the parallel collection of socioeconomic, caregiving, health and nutrition data will allow us to stratify how individual trajectories of habituation and recovery of response to novelty associate with different risk factors and adaptive mechanisms in greater depth. Given the increasing interest in the use of neuroimaging methods within global neurocognitive developmental studies, this study provides a novel cross‐culturally appropriate paradigm for the study of brain responses associated with attention and learning mechanisms across early development.     

Fine motor skill predicts expressive language in infant siblings of children with autism

We investigated whether fine motor and expressive language skills are related in the later‐born siblings of children with autism (heightened‐risk, HR infants) who are at increased risk for language delays. We observed 34 HR infants longitudinally from 12 to 36 months. We used parent report and standardized observation measures to assess fine motor skill from 12 to 24 months in HR infants (Study 1) and its relation to later expressive vocabulary at 36 months in HR infants (Study 2). In Study 1, we also included 25 infants without a family history of autism to serve as a normative comparison group for a parent‐report fine motor measure. We found that HR infants exhibited fine motor delays between 12 and 24 months and expressive vocabulary delays at 36 months. Further, fine motor skill significantly predicted expressive language at 36 months. Fine motor and expressive language skills are related early in development in HR infants, who, as a group, exhibit risk for delays in both. Our findings highlight the importance of considering fine motor skill in children at risk for language impairments and may have implications for early identification of expressive language difficulties.     

Early gray-matter and white-matter concentration in infancy predict later language skills: A whole brain voxel-based morphometry study

Magnetic Resonance Imaging (MRI) brain scans were obtained from 19 infants at 7 months. Expressive and receptive language performance was assessed at 12 months. Voxel-based morphometry (VBM) identified brain regions where gray-matter and white-matter concentrations at 7 months correlated significantly with children’s language scores at 12 months. Early gray-matter concentration in the right cerebellum, early white-matter concentration in the right cerebellum, and early white-matter concentration in the left posterior limb of the internal capsule (PLIC)/cerebral peduncle were positively and strongly associated with infants’ receptive language ability at 12 months. Early gray-matter concentration in the right hippocampus was positively and strongly correlated with infants’ expressive language ability at 12 months. Our results suggest that the cerebellum, PLIC/cerebral peduncle, and the hippocampus may be associated with early language development. Potential links between these structural predictors and infants’ linguistic functions are discussed.     

SES differences in language processing skill and vocabulary are evident at 18 months

This research revealed both similarities and striking differences in early language proficiency among infants from a broad range of advantaged and disadvantaged families. English‐learning infants (n = 48) were followed longitudinally from 18 to 24 months, using real‐time measures of spoken language processing. The first goal was to track developmental changes in processing efficiency in relation to vocabulary learning in this diverse sample. The second goal was to examine differences in these crucial aspects of early language development in relation to family socioeconomic status (SES). The most important findings were that significant disparities in vocabulary and language processing efficiency were already evident at 18 months between infants from higher‐ and lower‐SES families, and by 24 months there was a 6‐month gap between SES groups in processing skills critical to language development.     

Longitudinal Associations among Fathers' Perception of Coparenting,Partner Relationship Quality,and Paternal Stress during Early Childhood

This study examined the longitudinal and concurrent associations among fathers' perceptions of partner relationship quality (happiness, conflict), coparenting (shared decision making, conflict), and paternal stress. The sample consisted of 6,100 children who lived with both biological parents at 24 and 48 months in the Early Childhood Longitudinal Study‐Birth Cohort data set. The results showed that there are significant and concurrent associations between fathers' perceptions of the coparenting relationship and paternal stress, and between partner relationship quality and paternal stress. There was also a positive direct longitudinal association between partner relationship conflict and paternal stress. However, we found only one longitudinal cross‐system mediation effect: fathers' perception of coparenting conflict at 48 months mediated the association between partner relationship conflict at 24 months and paternal stress at 48 months. The family practice implications of these findings are discussed.     

Word comprehension mediates the link between gesture and word production: Examining language development in infant siblings of children with autism spectrum disorder

Children's gesture production precedes and predicts language development, but the pathways linking these domains are unclear. It is possible that gesture production assists in children's developing word comprehension, which in turn supports expressive vocabulary acquisition. The present study examines this mediation pathway in a population with variability in early communicative abilities—the younger siblings of children with autism spectrum disorder (ASD; high‐risk infants, HR). Participants included 92 HR infants and 28 infants at low risk (LR) for ASD. A primary caregiver completed the MacArthur‐Bates Communicative Development Inventory (Fenson, et al., 1993) at 12, 14, and 18 months, and HR infants received a diagnostic evaluation for ASD at 36 months. Word comprehension at 14 months mediated the relationship between 12‐month gesture and 18‐month word production in LR and HR infants (ab = 0.263; p < 0.01). For LR infants and HR infants with no diagnosis or language delay, gesture was strongly associated with word comprehension (as = 0.666; 0.646; 0.561; ps < 0.01). However, this relationship did not hold for infants later diagnosed with ASD (a = 0.073; p = 0.840). This finding adds to a growing literature suggesting that children with ASD learn language differently. Furthermore, this study provides an initial step toward testing the developmental pathways by which infants transition from early actions and gestures to expressive language.     

Altered White-Matter Microstructure in Conduct Disorder Is Specifically Associated with Elevated Callous-Unemotional Traits

Adolescents with conduct disorder (CD) and elevated callous-unemotional (CU) traits have been reported to present with a more severe and persistent pattern of antisocial behaviour than those with low levels of CU traits. However, relatively few studies have investigated whether there are differences in brain structure between these subgroups.We acquired diffusion tensor imaging data and used tract-based spatial statistics (TBSS) to compare adolescents with CD and high levels of CU traits (CD/CU+; n?=?18, CD and low levels of CU traits (CD/CU-; n?=?17) and healthy controls (HC; n?=?32) on measures of fractional anisotropy (FA), axial (AD), radial (RD) and mean (MD) diffusivity. Compared to CD/CU- adolescents, those with CD/CU+ presented increased FA and reduced RD and MD (lower diffusivity) in several tracts including: body and splenium of the corpus callosum, right inferior longitudinal fasciculus, ILF; right inferior fronto-occipital fasciculus, IFOF; left superior longitudinal fasciculus, SLF; left cerebral peduncle, bilateral internal capsule, left superior and posterior corona radiata, bilateral thalamic radiation and left external capsule. In addition, relative to CD/CU- individuals, adolescents with CD/CU+ showed lower diffusivity (indexed by reduced RD and MD) in left uncinate fasciculus and bilateral fornix. Finally, relative to healthy controls, CD/CU+ individuals showed lower diffusivity (reduced RD) in the genu and body of the corpus callosum and left anterior corona radiata. These results suggest that CD/CU+ individuals present with white-matter microstructural abnormalities compared to both CD/CU- individuals and age-matched healthy controls. This finding is consistent with emerging evidence suggesting that CD/CU+ represents a distinct subtype of CD, and illustrates the importance of accounting for heterogeneity within CD populations.     

Maternal perinatal representations and their associations with mother–infant interaction and attachment: A longitudinal comparison of Portuguese and Brazilian dyads

Prior research in Western countries (mostly the US, Canada and northern Europe) indicates that mothers' representations are associated with mother–infant interaction quality and their child's attachment security later in the first year. Fewer studies, however, have evaluated whether these associations hold for mother–infant dyads in other countries, such as Brazil and Portugal. Although these countries share a similar language and culture, they differ on societal dimensions that may affect parenting attitudes and mother–infant relationships, such as economic stress, social organisation, social policy, and the availability of services for young families. In this longitudinal study, we followed two independent samples of Brazilian and Portuguese mother–infant dyads from the perinatal period to 12 months post-partum. We assessed mothers' perinatal representations using semi-structured interviews in the first 48 hours after the infant's birth, and evaluated the associations of these representations with mother interaction quality at 9 months and infant attachment at 12 months. Results were similar in each country, corroborating prior research in single Western countries: Mothers with more positive perinatal representations were more sensitive to their infants during free play at 9 months and were more likely to have infants classified as securely attached at 12 months.     

Vocabulary growth rate from preschool to school‐age years is reflected in the connectivity of the arcuate fasciculus in 14‐year‐old children

The acquisition of language involves the functional specialization of several cortical regions. Connectivity between these brain regions may also change with the development of language. Various studies have demonstrated that the arcuate fasciculus was essential for language function. Vocabulary learning is one of the most important skills in language acquisition. In the present longitudinal study, we explored the influence of vocabulary development on the anatomical properties of the arcuate fasciculus. Seventy‐nine Chinese children participated in this study. Between age 4 and age 10, they were administered the same vocabulary task repeatedly. Following a previous study, children's vocabulary developmental trajectories were clustered into three subgroups (consistently good, catch‐up, consistently poor). At age 14, diffusion tensor imaging data were collected. Using ROI‐based tractography, the anterior, posterior and direct segments of the bilateral arcuate fasciculus were delineated in each child's native space. Group comparisons showed a significantly reduced fractional anisotropy in the left arcuate fasciculus of children in the consistently poor group, in particular in the posterior and direct segments of the arcuate fasciculus. No group differences were observed in the right hemisphere, nor in the left anterior segment. Further regression analyses showed that the rate of vocabulary development, rather than the initial vocabulary size, was a specific predictor of the left arcuate fasciculus connectivity.     

Microstructural integrity of the corpus callosum linked with neuropsychological performance in adolescents

Background: Diffusion tensor imaging (DTI) has revealed microstructural aspects of adolescent brain development, the cognitive correlates of which remain relatively uncharacterized. Methods: DTI was used to assess white matter microstructure in 18 typically developing adolescents (ages 16–18). Fractional anisotropy (FA) and mean diffusion (MD) were evaluated within the splenium and body of the corpus callosum in relation to cognitive performance. Results: Visuospatial construction abilities were associated with white matter integrity in both the splenium and body of the corpus callosum, while only splenium integrity was associated with language and psychomotor function. Conclusion: Results suggest that, for typically developing adolescents, white matter coherence positively relates to visuospatial, psychomotor, and language skills. These findings may have implications for the cognitive functioning of clinical populations in which typical white matter development is altered.     

Mechanisms linking height to early child development among infants and preschoolers in rural India

Stunting has been negatively associated with children's development. We examined the range of height by testing hypotheses: (a) height is positively associated with children's development, with associations moderated by inflammation and (b) home environments characterized by nurturance and early learning opportunities is positively associated with children's development over time and attenuate associations with height. Data included 513 infants (mean age 8.6 months) and 316 preschoolers (mean age 36.6 months) in rural India from a randomized controlled trial of multiple micronutrient powders (MNPs). Measures included height (height‐for‐age z‐scores based on WHO standards), inflammation (C‐reactive protein concentration >5 mg/L), nurturance (HOME Inventory), child development (Mullens Scales of Early Learning), and inhibitory control (preschoolers). Linear mixed effects models accounting for repeated measures, clustering, and confounders were used to assess associations between height and child development over time (infants: enrollment, 6 and 12 months; preschoolers: enrollment and 8 months). Moderating effects of inflammation and nurturance were tested with interaction terms. Among infants and preschoolers, height and nurturance were positively associated with all domains of child development over time, with the exception of inhibitory control. Among preschoolers, in the presence of inflammation, height was not associated with child development. Among infants, but not preschoolers, a nurturant home environment attenuated significant associations between height with fine motor and receptive language development. The mechanisms associated with children's development over time are multifactorial and include direct and indirect associations among nutrition, health, and the home environment, as supported by the Nurturing Care Framework.     

Sensitivity to amplitude envelope rise time in infancy and vocabulary development at 3 years: A significant relationship

Here we report, for the first time, a relationship between sensitivity to amplitude envelope rise time in infants and their later vocabulary development. Recent research in auditory neuroscience has revealed that amplitude envelope rise time plays a mechanistic role in speech encoding. Accordingly, individual differences in infant discrimination of amplitude envelope rise times could be expected to relate to individual differences in language acquisition. A group of 50 infants taking part in a longitudinal study contributed rise time discrimination thresholds when aged 7 and 10 months, and their vocabulary development was measured at 3 years. Experimental measures of phonological sensitivity were also administered at 3 years. Linear mixed effect models taking rise time sensitivity as the dependent variable, and controlling for non‐verbal IQ, showed significant predictive effects for vocabulary at 3 years, but not for the phonological sensitivity measures. The significant longitudinal relationship between amplitude envelope rise time discrimination and vocabulary development suggests that early rise time discrimination abilities have an impact on speech processing by infants.     

The development of stranger fear in infancy and toddlerhood: normative development,individual differences,antecedents, and outcomes

Despite implications that stranger fear is an important aspect of developing behavioral inhibition, a known risk factor for anxiety, normative and atypical developmental trajectories of stranger fear across infancy and toddlerhood remain understudied. We used a large, longitudinal data set (N = 1285) including multi‐trait, multi‐method assessments of temperament to examine the normative course of development for stranger fear and to explore the possibility that individual differences exist in trajectories of stranger fear development between 6 and 36 months of age. A latent class growth analysis suggested four different trajectories of stranger fear during this period. Stable, high levels of stranger fear over time were associated with poorer RSA suppression at 6 months of age. Rates of concordance in trajectory‐based class membership for identical (monozygotic) and fraternal (dizygotic) twins, along with associations between atypical stranger fear development and greater anxiety‐related maternal characteristics, suggested that individual differences in developmental trajectories of stranger fear may be heritable. Importantly, trajectories of stranger fear during infancy and toddlerhood were linked to individual differences in behavioral inhibition, with chronically high levels of stranger fear and sharp increases in stranger fear over time related to greater levels of inhibition than other developmental trajectories.     

Early language development after peri-natal stroke

Early unilateral brain damage has different implications for language development than does similar damage in adults, given the plasticity of the developing brain. The goal of this study was to examine early markers of language and gesture at 12 and 24 months in children who had peri-natal right hemisphere (RH) or left hemisphere (LH) stroke (n = 71), compared with typically developing controls (n = 126). Parents completed the MacArthur-Bates Communicative Development Inventory (CDI): Words & Gestures (12 month data point), or the CDI: Words & Sentences (24 month data point). Statistical analyses were performed on percentile scores using analysis of variance techniques. At 12 months, there were no differences among groups for Words Understood, Phrases Understood or Words Produced. At 24 months, both lesion groups scored significantly lower than controls on Word Production, Irregular Words, and Mean Length of Sentences, but lesion groups did not differ from each other. In a longitudinal subset of participants, expressive vocabulary failed to progress as expected from 12 to 24 months in the stroke group, with no differences based on lesion side. Gesture and word production were dissociated in the left hemisphere subjects. Findings suggest that early language development after peri-natal stroke takes a different course from that of typical language development, perhaps reflecting brain reorganization secondary to plasticity in the developing brain.     

Influences of vowel and tone variation on emergent word knowledge: a cross‐linguistic investigation

To learn words, infants must be sensitive to native phonological contrast. While lexical tone predominates as a source of phonemic contrast in human languages, there has been little investigation of the influences of lexical tone on word learning. The present study investigates infants’ sensitivity to tone mispronunciations in two groups of infants. For one group (Chinese learners), tone is phonemic in their native language, and for the second group (English learners), tone is non‐phonemic and constituted suprasegmental variation. In Experiment 1, English learners were trained on novel word–object pairings and tested on their recognition of correct pronunciations, tone and vowel mispronunciations of these words at 18 and 24 months. In Experiment 2a, bilingual English‐Chinese learners were tested on a similar task translated into Chinese at the same age intervals. Results demonstrate that non‐tonal learners treated tonal and vowel substitutions alike as mispronunciations at 18 months but only treated vowel substitutions as mispronunciations at 24 months. Tonal learners treated both tonal and vowel substitutions as mispronunciations at both ages. In Experiment 2b, bilingual non‐tone language learners were tested on the same set of tasks replicating a similar set of results as monolingual non‐tone language learners (Experiment 1). Findings point to an early predisposition to treat tone as a defining characteristic of words regardless of its lexical relevance at 18 months. Between 18 and 24 months, learners appear to ascribe lexical relevance to tone in a language‐specific manner. The current study identifies the influences of tone variation on memories for newly learned words and the time period during which lexical tone – a highly frequent constituent of human languages – actually becomes lexical for early learners. Findings are contextualized with prevailing models of the developing lexicon.     

Infants’ statistical word segmentation in an artificial language is linked to both parental speech input and reported production abilities

Individual variability in infant's language processing is partly explained by environmental factors, like the quantity of parental speech input, as well as by infant‐specific factors, like speech production. Here, we explore how these factors affect infant word segmentation. We used an artificial language to ensure that only statistical regularities (like transitional probabilities between syllables) could cue word boundaries, and then asked how the quantity of parental speech input and infants’ babbling repertoire predict infants’ abilities to use these statistical cues. We replicated prior reports showing that 8‐month‐old infants use statistical cues to segment words, with a preference for part‐words over words (a novelty effect). Crucially, 8‐month‐olds with larger novelty effects had received more speech input at 4 months and had greater production abilities at 8 months. These findings establish for the first time that the ability to extract statistical information from speech correlates with individual factors in infancy, like early speech experience and language production. Implications of these findings for understanding individual variability in early language acquisition are discussed.