Children with Autism Spectrum Disorder (ASD) tend to have lower gray matter thickness and greater gyrification in specific brain regions involved in language function, according to new research published in Scientific Reports.
The study also found that language abilities were associated with these structural brain differences in children with ASD. The results challenge the idea that atypical brain development in ASD normalizes by middle childhood.
“Despite the fact that language is one of the most complex systems in the brain, most children efficiently aсquire their native language during the first few years of life. However, there is a population of kids who do not fully acquire language,” said study author Vardan Arutiunian, a postdoctoral fellow at the Center for Child Health, Behavior and Development at Seattle Children’s Research Institute.
“According to the Centers for Disease Control and Prevention (USA), the prevalence of ASD is about 1 out of 50 children and language impairment is one of the most common co-occurring conditions (although it is not among the core diagnostic criteria). At the same time, the neurobiological basis of language variation in children with ASD is still not clearly understood. The idea to explore the relationship between different structural brain characteristics and language skills in school-aged children with ASD initiated this study.”
The researchers used a method called structural magnetic resonance imaging (MRI) to examine the brains of 8-to-14-year-old children with ASD and compare them to typically developing children of the same age and sex. The study included 18 children with ASD and 18 typically developing children as a control group. All the children were right-handed and native Russian speakers. The children with ASD were recruited from a center specializing in supporting children with ASD, while the typically developing children were recruited from public schools in Moscow.
The researchers examined both volume-based measures (such as gray matter, white matter, and cerebrospinal fluid volumes) and surface-based measures (such as thickness, gyrification index, sulcus depth, and fractal dimension of the brain’s outer surface).
Gray matter refers to the brain tissue that contains the cell bodies of neurons, while white matter consists of nerve fibers that connect different brain regions. Cerebrospinal fluid is a clear fluid that surrounds and protects the brain.
Cortical thickness refers to the thickness of the brain’s outer layer, and gyrification index measures the amount of folding on the brain’s surface. Sulcus depth is the measurement of the grooves on the brain, and fractal dimension quantifies the complexity of the brain’s folding patterns.
The researchers measured the non-verbal IQ of the children with ASD using standardized tests, and the typically developing children’s non-verbal intelligence was screened using a different test. The language abilities of all children were assessed using a standardized test that evaluated different aspects of language production and comprehension.
The study found several differences in the brains of children with ASD compared to typically developing children. The ASD group showed alterations in multiple brain regions in terms of both volume and surface characteristics. Total gray matter volume was significantly reduced in children with ASD compared to typically developing children, particularly in certain regions of the right hemisphere. Gray matter thickness was also decreased in various regions of both hemispheres in children with ASD.
But when exploring the relationship between brain characteristics and language abilities in children with ASD, the researchers found that only decreased gray matter thickness and increased gyrification in language-related brain regions were associated with more severe language impairment. Other brain characteristics such as gray matter and white matter volumes, as well as sulcus depth, did not show significant associations with language abilities in these regions.
“There are different neurobiological metrics (e.g., grey / white matter volumes, grey matter thickness, sulcus depth, etc.),” Arutiunian told PsyPost. “Not all of them are altered in children with ASD and not all of them are associated with language impairment in ASD. Specifically, according to the results of our study, the alterations of only grey matter thickness and gyrification in language-related brain areas were related to language skills in children with ASD.”
The study provided evidence against the theory of brain “normalization” during middle childhood among autistic individuals. The results showed that children with autism still exhibited atypical brain features, including reduced gray matter volume and thickness, as well as altered gyrification patterns, indicating that these characteristics were not normalized or diminished with age.
“Our findings contradict the theory that early atypical brain development in children with autism normalizes by middle school age (7-10 years old),” said co-author Alina Minnigulova, a junior research fellow at HSE University in Moscow.
“To determine the age at which the nervous system may be restored, we need to continue studying not only toddlers and preschoolers with ASD, but also school-aged children and adults with ASD, given that the developmental characteristics of their nervous system may differ. Research on these latter two groups has been very limited thus far.”
The study sheds light on brain differences related to language abilities in school-aged children with ASD. Understanding the specific structural characteristics related to language impairments can inform the design of tailored educational programs for children with autism.
But it is still unclear how these differences develop over time. For example, it would be valuable to investigate whether measures like cortical thickness or gyrification in language-related brain areas can predict language skills at different ages. Future research could conduct long-term studies to explore how these brain characteristics change with age and how they relate to language difficulties in individuals with ASD.
The study, “Structural brain abnormalities and their association with language impairment in school-aged children with Autism Spectrum Disorder“, was authored by Vardan Arutiunian, Militina Gomozova, Alina Minnigulova, Elizaveta Davydova, Darya Pereverzeva, Alexander Sorokin, Svetlana Tyushkevich, Uliana Mamokhina, Kamilla Danilina, and Olga Dragoy.