Study Shows Brain Structures Grow Differently in Boys and Men with Autism

It remains a bit of a mystery exactly what is different about the brains of people with autism versus the brains of neurotypical people, but researchers are getting closer to having some answers about this phenomenon. Now a new study suggests a pattern of brain development in boys and men with autism that doesn’t exist in boys and men without autism.

The study, which used magnetic resonance imaging (MRI) scans over a 16-year-period, determined that males with autism show unique patterns in brain development.

At the beginning of the study, participants ranged in age from six to 45 years. 73 percent of autistic individuals and 50 percent of non-autistic individuals stayed for the duration of the study, while others left and were replaced with new participants.

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This research is an addition to a previous eight-year study and uses some of the same participants. Scientists scanned the brains of 105 autistic and 125 non-autistic boys and men at different time points from 2003 to 2019.

“With the addition of these time points, we now see that these non-uniform regional volumetric differences really persist into very late childhood,” says co-lead investigator Brandon Zielinski, associate professor of pediatrics and neurology at the University of Utah in Salt Lake City.

The researchers discovered that boys with autism tended to have more gray matter in early childhood than other boys, but this phenomenon more or less cleared up by age 12. On the other hand, however, their ventricles, which contain and transport cerebrospinal fluid, were the same size as the controls at the beginning of the study but began expanding by the age of 21.

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Additionally, the corpus callosum, a cord of nerve fibers that runs between the two hemispheres of the brain, grew more slowly in individuals with autism and tended to be smaller than that of the controls by the time participants reached age 36.

Eric Courchesne, professor of neuroscience at the University of California, San Diego, says these findings, for the most part, replicate previous research. “But they’ve done it a different way. They’ve improved it,” he says. “And that shows the process of science.”

Researchers then divided their autistic participants into two subgroups. 61 individuals still met the diagnostic criteria for autism according to their Autism Diagnostic Observation Schedule scores, but 17 did not anymore. In this group, those who still met the criteria for autism had a smaller corpus callosum than those who did not meet the criteria.

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Molly DuBray Prigge, a research associate in Zielinski’s lab, calls this difference found within the autism group “really interesting.”

“Now we’re wanting to look back and see how stable are these individuals [who no longer meet the diagnostic criteria]?” she says. “If we brought them back in two years, would they also still no longer meet criteria for [autism]?”

Most imaging studies done in people with autism are cross-sectional, meaning they only capture scans from participants of different ages a single time. This is one of the only studies of its kind to be longitudinal, meaning it examines each individual’s development over time.

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“Looking at those within-subject changes is really important,” says Carrie Bearden, professor of psychiatry and biobehavioral sciences and of psychology at the University of California, Los Angeles, who was not involved in the study. “It’s so hard to get these long, multiple-time-point studies.”

The study was published in the journal NeuroImage. So far, however, the research does not point to a reason why these structural differences exist in the brains of men and boys with autism. Further research and different scanning techniques will hopefully shed more light on this issue in the future.

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