Early Signs of Autism
July 27, 2012 § Leave a comment
Researchers at the Washington University School of Medicine in St. Louis, the University of North Carolina at Chapel Hill, and others, have discovered a substantial disparity between the brain development of 6-month-old infants who later develop autism and infants who do not develop the disorder. The study embodies the latest findings from the Infant Brain Imaging Study Network, an initiative funded by the National Institutes of Health.
“We were surprised that there were so many differences so early in infancy,” said co-author Kelly N. Botteron, M.D., who is heading the endeavor at the Washington University site. The study in which these findings originated, published online in the American Journal of Psychiatry, involved infants with older siblings who had developed autism. These infants were considered high risk because the disorder was prevalent in their family.
The study involved nocturnal brain scans, which the researchers performed while the infants slept. 92 infants who had previously completed Diffusion Tensor Imaging (DTI) at 6 months of age were scanned. They were then given a behavioral assessment at 24 months of age. By the time the infants had reached 24 months, 30% of them were meeting criteria to place them in the autism spectrum. These findings suggest not only that autism develops over time, beginning in infancy, but also that the disorder may be detectable in infants as early as 6 months old.
Scans of the infants with autism uncovered evidence that there were changes in the pathways that connect brain regions to one another. There were significant changes to multiple fiber pathways in the brain’s white matter. Using DTI-assessed Fractional Anistropy (FA), which measures the regulation of white matter by observing the movement of water molecules through brain tissues, researchers analyzed 15 tracts of white matter and found significant differences in 12 tracts among the infants who later developed autism. These differences were not found in those infants who did not develop the disorder. “The idea that connections may be less organized in children with autism fits with our hypothesis,” says Gouttard S. Botteron, child psychiatrist at St. Louis Children’s Hospital.
He goes on to explain that the direction and rate of water movement is controlled by the surrounding structures. In the white matter tracts, the water has to flow in a particular direction to be parallel with the axons that connect different brain cells. “This highly constrained directional flow is characterized by higher FA,” he explains. This higher FA was found in 6-month-old infants who were later diagnosed with autism, but the FA values fell by the 24-month mark, indicating that these signs can only be detected early. Botteron expressed the team’s surprise at having found that almost every pathway examined showed these stark differences.
Jason J. Wolff, Ph.D., first author of the paper and a postdoctoral fellow at UNC’s Carolina Institute for Developmental Disabilities, says, “At this point, it’s a preliminary, albeit great, first step toward thinking about developing a biomarker for risk in advance of our current ability to diagnose autism.”
Researchers around North America are continuing Infant Brain Imaging Study on high-risk infants with funding from the National Institute of Child Health and Development of the National Institutes of Health, Autism Speaks, and the Simons Foundation.
Dryden, Jim. “Brain Differences Seen at 6 Months in Infants Who Develop Autism”. (February 17, 2012). Neuroscience News. February 18, 2012. http://neurosciencenews.com/brain-scans-6-months-infants-autism-diffusion-tensor-imaging-dti/.