A recent study conducted by UC Davis researchers discovered significant differences in brain development between boys and girls with autism aged 2-13. The study, which was published in Molecular Psychiatry, revealed sex-specific changes in the thickness of the cerebral cortex, the outer layer of the brain. These findings are particularly noteworthy as very few studies have examined the development of the cortex in autistic children.The development of autism in girls is not diagnosed as often as in boys, with nearly four males being diagnosed with autism for every one female. Christine Wu Nordahl, a professor at UC Davis MIND Institute, stated that the underdiagnosis of autism in females is a contributing factor to this sex bias. However, she also mentioned that biological differences play a role in this disparity. The cortex, which is the brain’s outer layer, is made up of distinct layers of neurons that fire in sync.The brain is an amazing organ that allows us to think, learn, solve problems, build memories, and experience emotions. Up until around age 2, the cortex thickens rapidly as new neurons are formed. After this peak, the outer cortical layer starts to thin. Previous research has shown that this thinning process is not the same in autistic children as it is in non-autistic children, but whether there are differences between autistic boys and girls had not been investigated.
Derek Andrews, the lead author, stated, “It’s important to understand how differences in brain development between boys and girls may interact with autistic development and lead to different developmental outcomes.”The study was conducted by an assistant project scientist who works in the Department of Psychiatry and Behavioral Sciences at the MIND Institute.
Changes in the cortex during childhood
A group of researchers examined the brain scans of 290 children with autism, including 202 boys and 88 girls, as well as 139 typically developing children without autism, including 79 boys and 60 girls. The children were categorized based on their sex at birth.
All of the participants were part of the MIND Institute’s Autism Phenome Project (APP), which is one of the most extensive longitudinal studies of autism in the world. The project also focuses on Girls with Autism.The GAIN study focuses on imaging neurodevelopment and aims to increase female representation in research. Researchers conducted MRI scans on girls between the ages of 2 and 13 at four different time periods. They discovered that at age 3, autistic girls had a thicker cortex than non-autistic girls, accounting for about 9% of the total cortical surface. This difference was much less apparent in autistic males compared to non-autistic males of the same age. Furthermore, autistic females exhibited faster rates of cortical thinning during middle childhood compared to males. These cortical differences were evident across various neural areas.l networks.
“The brain differences associated with autism were evident across almost all brain networks,” Andrews stated.
He was surprised to find that the differences were most significant at younger ages. As autistic girls showed a faster rate of cortical thinning, the disparities between autistic boys and girls became less noticeable by middle childhood.
“We usually assume that sex differences become more prominent after puberty. However, brain development between the ages of 2-4 is very dynamic, so even small changes in the timing of development between the sexes could lead to significant differences,” he explained.
The importance of studying both sexes over the long term
According to Andrews, it is clear from these findings that longitudinal studies that include both sexes are essential.
Nordahl emphasized the need for such studies, stating, “Had we only focused on boys at age 3, we might have concluded that there were no differences. Similarly, if we had only examined boys and girls at 11 years old, we might have thought that there were very few sex differences in the cortex. It was crucial to follow both boys and girls over time in order to gain a comprehensive understanding.”hl, who currently leads the APP, initiated the GAIN study in 2014. “The APP had a significantly large sample of approximately 150 autistic boys, but only around 30 autistic girls. This number of autistic girls was insufficient to thoroughly analyze how they may differ or resemble boys, so we made an effort to boost the representation of autistic females in our research,” she explained. GAIN is distinct, and Andrews expressed his desire for other researchers to also include more autistic girls in autism research. “Autistic females make up about 20% of the autistic population. Any effective attempt to comprehend autism will have to involve autistic females.” Co-The researchers involved in the study are Kersten Diers and Martin Reuter from the German Center for Neurodegenerative Diseases; Devani Cordero from Massachusetts General Hospital; and Joshua K. Lee, Danielle J. Harvey, Brianna Heath, Sally J. Rogers, Marjorie Solomon and David Amaral from UC Davis.
Funding for the study was provided by the National Institute of Mental Health (R01MH127046, R01MH128814 and R01MH103284), the National Institute of Child Health and Development (P50 HD093079) and the MIND Institute Intellectual and Developmental Disabilities Research Center (P50 HD103526)
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