This research, led by Jessica Girault, PhD, at the UNC School of Medicine, was conducted as part of the NIH-funded Infant Brain Imaging Study Network, which used MRI to document crucial differences in the visual processing system in infants’ brains. . was diagnosed with autism.
CHAPEL HILL, NC — For the first time, scientists have discovered that brain differences in the visual brain systems of babies later diagnosed with autism are linked to inherited genetic factors.
Published in the American Journal of Psychiatry, this study shows that brain changes in the size, white matter integrity, and functional connectivity of the visual processing systems of six-month-old children are apparent long before they show symptoms of autism as toddlers. In addition, the presence of brain changes in the visual system is associated with the severity of autism traits in their older siblings.
Led by Jessica Girault, PhD, assistant professor of psychiatry at the UNC School of Medicine, this is the first study to show that infants with older siblings who have autism and who later develop autism themselves as toddlers have specific biological differences. in visual processing regions of the brain, and that these brain features precede the onset of autistic symptoms. The presence of those visual processing differences is related to how pronounced the autism features are in the older siblings.
“We’re starting to analyze differences in infant brain development that may be related to genetic factors,” said Girault, who is also a member of the Carolina Institute of Developmental Disabilities (CIDD). “Using magnetic resonance imaging (MRI), we studied selected brain structures, the functional relationship between key brain regions and the microstructure of white matter connections between those brain regions. Findings from all three pointed us to the discovery of unique differences in the visual systems of infants who later developed autism.
As part of the NIH-funded Infant Brain Imaging Study (IBIS) Network, UNC-Chapel Hill and Washington University researchers led this first-of-its-kind study.
Behind baby’s eyes
When parents and babies bond, close their eyes and experience their world together day in and day out, it’s not just cute; this is how babies learn to interpret subtle signals about their environment. It’s how babies learn to relate a caregiver’s behavior to their own. This visual rhythm during the first years of life is crucial for cognitive, emotional and social development. In babies who develop autism, this research suggests that something goes wrong in the brain’s visual system that affects this visual interplay.
In recent years, IBIS Network researchers have used MRI to document brain differences in infants who later develop autism in the second year of life. In 2020, Girault’s research showed that younger siblings were much more likely to develop autism if their older autistic siblings had higher levels of autistic traits.
“This suggests that these autistic traits tell us something about the power of genetic factors for autism within a family,” Girault said. “But beyond that, we couldn’t say much. This current study takes our work a step forward.”
For this study, the researchers from the Infant Brain Imaging Study (IBIS) Network recruited 384 siblings. The older child in each pair had already been diagnosed with autism, leaving the little brother or sister
with a higher risk of developing autism. Next, the researchers used different MRI approaches to study the brains of the younger siblings, aged six, 12 and 24 months, in detail.
The researchers measured brain volume, the area of the brain’s surface, in the area of the brain involved in vision (the occipital cortex) — structures that this research team had previously shown to be altered in babies who developed autism as toddlers. They also examined the microstructure of the splenium’s white matter, a structure the researchers previously showed was related to how quickly babies orient themselves to visual stimuli in their environment. At the same time, researchers documented the level of autistic features in those babies’ older autistic siblings.
Girault and colleagues identified brain differences in two parts of the visual processing system — the occipital gyrus, which is important for object recognition, and the splenium, which is important for communication between different hemispherical parts of the visual system. The splenium is also crucial to quickly orient our attention to things we see around us.
“It is particularly noteworthy that we were able to demonstrate associations between brain findings in infants and the behavior of their older siblings with autism,” said co-senior author John R. Pruett, Jr., MD, PhD, professor of psychiatry at Washington University. School of Medicine. “The convergence of brain-wide, data-driven fcMRI results with the structural and diffusion findings strengthens our confidence in future replication of these discoveries, which can be tested in the new cohort of 250 high-familial-probability infants that we are currently recruiting.”
Co-senior author Joe Piven, MD, CIDD director, added: “We think that aberrant visual circuits are a fundamental cog in the cascade of events that lead to later autism. We think this circuit changes how babies experience the world, and how they experience the world changes how their brains develop next. It’s this secondary altered brain development that can result in what we call autism and typically shows up in the latter part of the first and second years of life.”
More research is needed, but this study points towards behavioral interventions targeting the visual and related brain systems in the first year of life in infants at greater risk of developing autism based on inherited risk factors. Such interventions would reduce the chance that children will develop certain more severe autism characteristics.
Co-senior authors are Joe Piven, MD, CIDD Director and Thomas E. Castelloe Distinguished Professor of Psychiatry and Pediatrics at UNC School of Medicine; John Constantino, MD, the Blanche F. Ittleson Professor of Psychiatry and Pediatrics and at Washington University School of Medicine and Psychiatrist-in-Chief at St. Louis Children’s Hospital; and John R. Pruett, Jr., MD, PhD, professor of psychiatry at Washington University School of Medicine.
This research was supported by grants from the National Institutes of Health (K01-MH122779, R01-HD055741, T32-HD040127, P30-HD003110, R01-MH118362, MH118362-02S1, and P30-NS098577), and by the Simons Foundation (140209) .
The authors are grateful to all families and children who participated in the Infant Brain Imaging Study (IBIS) study. The IBIS Network is an NIH-funded Autism Center of Excellence project and consists of a consortium of nine universities in the United States and Canada.
Media contact: Mark Derewicz919-923-0959