A new study shows that infants who go on to develop autism take longer to shift their gaze between images than do infants who develop normally. The investigators detected the delay in 7-month-old babies and linked it to differences in a part of the brain associated with visual processing.
The study appears online today in The American Journal of Psychiatry and was supported in part by Autism Speaks.
“Not only did we find a behavioral difference in very young infants, but we may have discovered a brain mechanism to potentially explain the behavioral difference,” says the study’s lead author Jed Elison, Ph.D. Dr. Elison completed the research at the University of North Carolina, with senior author and psychiatrist Joseph Piven, M.D. Dr. Elison is now a post-doctoral fellow at the California Institute of Technology.
Experts have proposed that normal social and cognitive development begins with an infant’s ability to adeptly shift attention to important cues. For example, infants normally look to their mother’s face when she calls their name. When looking at their mother’s eyes, they’ll shift their gaze to follow hers. These are stepping stones toward more complex social and cognitive skills, which begin to appear between 9 and 10 months of age.
Dr. Elison and colleagues looked at differences in gaze shifting, also called “visual orienting,” at 7 months to see if it was associated with later development of autism spectrum disorder (ASD). The participating infants were part of Dr. Piven’s larger Infant Brain Imaging Study (IBIS). Of these, 56 infants were at risk for developing ASD because they had older siblings on the autism spectrum. For comparison, the study also included 41 babies from families unaffected by the disorder.
The researchers tracked the time it took for the 7-month-old babies to shift their gaze as different images appeared across a computer monitor. Each baby also had a brain scan and, at 25 months, was assessed for ASD.
The results showed that those infants who were diagnosed with ASD at 25 months had a slower gaze shift at 7 months, compared to infants who did not develop ASD. This was true regardless of whether the infants came from “high risk” or “low risk” families.
The brain scans provided further insights. They involved a type of magnetic resonance imaging (MRI) called diffusion tensor imaging. The researchers used it to take snapshots of a part of the brain called the splenium of the corpus callosum. It is associated with visual processing and contains bundles of brain nerve fibers called “white matter.”
In low-risk infants who did not develop autism, the researchers found a strong and specific association between adept gaze shifting and the organization of a specific tract of nerve fibers in the splenium. “This suggests to us that this neural circuit is supporting this behavior in low-risk infants,” Dr. Elison says.
In the babies who went on to develop autism, however, there was no such association between the neural circuit’s organization and adeptness in gaze shifting. “This allows us to make the conservative, but important claim that the splenium may not be supporting visual orienting in infants who later develop autism,” Dr. Elison says. “At least it’s not doing so in the same manner that it does in low-risk, typically developing infants.”
The new findings build on the IBIS team’s prior research, which found significant differences in white matter development between babies who went on to develop ASD and those who did not. “That was our first foray into brain development of infants who later develop autism,” Dr. Elison says. “This study takes it a step further by looking at a very specific behavior and the brain mechanism that should be supporting that behavior.”
Going forward, the team hopes to determine whether a visual orienting test could aid in the early detection of ASD in infants. It also might be possible that early interventions targeted at helping infants shift gaze would have broader benefits. “More adept and efficient gaze shifting during this period of infancy may facilitate later social and cognitive development,” Dr. Elison says. As part of the IBIS study, the researchers also plan to continue their work on visual orienting with younger babies.
“The discovery of early biomarkers of autism moves us closer to both understanding autism’s development and being able to identify infants at risk for autism at the earliest point possible,” says Autism Speaks Chief Science Officer Geraldine Dawson, Ph.D. Dr. Dawson is also a professor of psychiatry at the University of North Carolina and a collaborator on the IBIS team’s earlier study.
Last year, the IBIS researchers identified the first presymptom brain marker of autism in infants as young as 6 months. Autism Speaks is supporting this work through a research grant that funds collaboration between the IBIS and EARLI study groups. You can explore these and other Autism Speaks studies using this website’s grant search.