Beginning at 6 months of age, high-risk infants — who would later develop autism — display major brain differences compared to high-risk infants who would not develop autism, according to a new study led by the University of North Carolina at Chapel Hill.
“It’s a promising finding,” said Jason J. Wolff, PhD, lead author of the study and a postdoctoral fellow.
“At this point, it’s a preliminary albeit great first step towards thinking about developing a biomarker for risk in advance of our current ability to diagnose autism.”
The study also suggests, said Wolff, that autism does not appear suddenly in young children, but rather develops gradually during infancy. This raises the possibility “that we may be able to interrupt that process with targeted intervention,” he said.
The study included 92 infants who all have older siblings with autism and are therefore considered at high risk for autism as well. All underwent diffusion tensor imaging — a type of magnetic resonance imaging (MRI) — at 6 months and behavioral assessments at 24 months. Most also had additional brain imaging scans at either or both 12 and 24 months.
At 24 months, 28 infants (30 percent) met criteria for autism spectrum disorders while 64 infants (70 percent) did not.
Fractional anisotropy (FA) revealed that the two groups differed in white matter fiber tract development — pathways that connect brain regions. FA measures white matter organization and development by tracking water molecule movement through brain tissue.
Between infants who did develop autism versus infants who did not, significant differences were found in FA trajectories in 12 of the 15 tracts that were studied.
Specifically, babies who later developed autism had elevated FA at six months but then had slower change over time. By 24 months of age, infants with autism had lower FA values than infants without autism.
“This evidence, which implicates multiple fiber pathways, suggests that autism is a whole-brain phenomenon not isolated to any particular brain region,” Wolff said.
The study was published online at AJP in Advance, a section of the website of the American Journal of Psychiatry. Its results are the latest from the ongoing Infant Brain Imaging Study (IBIS) Network.