Neural Precursors of Language in Infants at High Risk for Autism Spectrum Disorder

Background: Autism spectrum disorder (ASD) is a developmental disorder characterized by difficulties in social interaction and communication. One in 5 infants with an older sibling with ASD will develop this disorder, compared to the rate of 1 in 68 in the general population. However, a subset of siblings who do not develop ASD may also exhibit a variety of developmental delays/problems, including language impairments. Research on children with ASD and their siblings has repeatedly shown that those who develop stronger language abilities have more positive outcomes. One strategy for improving language is to get children at risk for ASD into effective and appropriately targeted educational interventions in the very earliest stages of life, when precursors of language and other social behaviors are developing. However, ASD is currently not diagnosed until children have reached 2 or 3 years of age.

Objectives: In this study, we first investigate neural precursors of language acquisition as potential biomarkers of atypical development in 3-month-old infants at high risk for ASD. We then examine whether these biomarkers predict children’s language and communicative outcomes at 18 months of age. 

Methods: Participants were drawn from a larger sample of infants enrolled in an ongoing, longitudinal, prospective study of early development in siblings of children with ASD.  Three month olds with high (HRA; n=21) and low (LRC; n=17) familial ASD risk were imaged using functional near-infrared spectroscopy while they listened to speech-like stimuli containing syllable repetitions or control syllable sequences (see Gervain et al., 2008). We analyzed their neural responses to these stimuli over left and right temporal regions to determine whether biomarkers of atypical language development are present the first few months of life. We then used multiple and ordinal linear regression techniques to investigate whether 3-month-old neural activity predicts children’s 18-month expressive and receptive language (measured by the Mullen Scales of Early Learning [MSEL] and the MacArthur-Bates Communicative Development Inventory: Words and Sentences Module [MCDI]), and autism symptomatology (measured by Autism Diagnostic Observation Schedule severity scores) outcomes. 

Results: While LRC infants showed initial neural activation that decreased over exposure to repetition-based language stimuli, potentially indicating a habituation response to repetition in speech, HRA infants showed no changes in their neural activity to these stimuli over exposure (F(1,33) = 6.77, p[sequence*exposure*risk*gender]=0.014). This 3-month-old neural activity predicted 18-month MSEL expressive language (0.001<p<0.045) and MCDI early gesture scores  (0.004<p<0.041) in both LRC and HRA groups; in some cases, these associations also differed for males and females.

Conclusions: Putative precursors of language acquisition are disrupted in children at high risk for ASD from as young as 3 months of age. The current research thus identifies neural biomarkers that may be specific to language development, and which, with future research and educational application, may aid in determining which children are most likely to benefit from placement into language-based educational intervention programs from the very first months of life.