Summary: Infants who were later diagnosed with autism spectrum disorder (ASD) at 24 months showed measurable differences in brain regions responsible for visual processing as early as six months of age, according to a new NIH-funded study.
Source: NIH
Researchers found that infants who went on to receive an ASD diagnosis at 24 months already displayed differences in the brain’s visual processing areas at six months, suggesting early emerging neural signatures that may influence social development and learning.
The research team proposes that altered visual processing in infancy could change how babies perceive and engage with their environment and caregivers. Such differences in early sensory processing may cascade into altered patterns of attention, interaction, and learning that contribute to the emergence of ASD symptoms over time.
This study, led by Jessica Girault, Ph.D., at the University of North Carolina School of Medicine, Chapel Hill, is published in the American Journal of Psychiatry and was funded by the National Institutes of Health (NIH).
The investigators enrolled 384 pairs of siblings in which an older child (the proband) had been diagnosed with ASD. Prior work by the team showed that the likelihood for a younger sibling to develop ASD is higher when the older sibling presents more pronounced ASD traits. Using this family-based design allowed the researchers to examine how inherited liability and proband symptom severity relate to early brain development in younger siblings.
Participants underwent Magnetic Resonance Imaging (MRI) at three time points: 6, 12, and 24 months of age. The imaging protocol targeted multiple brain measures relevant to early development and ASD, including total cerebral volume, cortical surface area, measures of extra-axial cerebrospinal fluid, occipital (visual) cortical surface area, and white matter microstructure in the splenium, a key fiber bundle connecting left and right visual cortices.
Among the 89 younger siblings who were later diagnosed with ASD, the study found that those whose older siblings exhibited more severe ASD traits showed distinct patterns of brain structure and connectivity. Specifically, these infants had greater total cerebral volume and larger cortical surface area overall, as well as a larger surface area in parts of the visual cortex involved in object recognition. In addition, they showed evidence of less mature white matter microstructure in the splenium, which could reflect delayed or altered development of interhemispheric visual connections and visual attention systems.
In complementary analyses using functional connectivity MRI at six months, the researchers observed weaker functional coupling between visual processing regions and several broader brain networks across the infant cohort. These convergent anatomical and functional findings point to early differences in the development of visual circuitry that relate to familial measures of ASD traits.
The authors interpret these results as evidence that inherited liability for ASD may shape early, prodromal development of neural systems supporting visual perception and attention. Disruptions in these systems during a sensitive window of infancy could alter how infants sample and learn from their social and sensory environment, potentially contributing to the behavioral features that define ASD.
Funding: Support for this research came from NIH through the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the National Institute of Mental Health, and the National Institute of Neurological Disorders and Stroke.
About this ASD research news
Author: Robert Bock
Source: NIH
Contact: Robert Bock – NIH
Image: The image is in the public domain
Original Research: Open access.
“Infant Visual Brain Development and Inherited Genetic Liability in Autism” by Girault, JB et al. American Journal of Psychiatry
Abstract
Infant Visual Brain Development and Inherited Genetic Liability in Autism
Objective:
Autism spectrum disorder (ASD) shows familial aggregation, and younger siblings of children with ASD are at elevated risk. Prior prospective MRI work suggests atypical brain development can precede clinical diagnosis, but the relationship between early brain maturation and familial genetic liability is not fully understood. Because recurrence risk within families is related to the severity of ASD traits in the proband, the investigators examined how proband trait levels relate to early brain development in younger siblings.
Methods:
In a cohort of 384 proband-sibling pairs (89 pairs where the younger sibling was diagnosed with ASD), the study assessed associations between proband ASD trait severity and sibling brain measures at 6, 12, and 24 months. Key MRI phenotypes included total cerebral volume, cortical surface area, extra-axial cerebrospinal fluid, occipital cortical surface area, and splenium white matter microstructure. Findings from the primary anatomical analyses motivated follow-up data-driven analyses of functional connectivity at six months to evaluate network-level differences.
Results:
Higher levels of ASD traits in the proband were linked to larger total cerebral volume and greater cortical surface area in younger siblings who developed ASD. These siblings also showed enlarged surface area in occipital visual regions and reduced white matter integrity in visual system components, consistent with less mature interhemispheric visual connections. Functional connectivity analyses revealed weaker coupling between the visual system and several networks across infancy, aligning with the structural observations.
Conclusions:
The results support the view that specific early MRI phenotypes associated with ASD reflect quantitative familial variation in ASD traits. Multimodal evidence converges on cortical regions, fiber pathways, and functional networks that support visual processing, suggesting that inherited liability contributes to early differences in the developmental trajectory of visual circuitry in infants at familial risk for ASD. These findings highlight the importance of early sensory and perceptual development in understanding the neurodevelopmental pathways that precede ASD diagnosis.