The Brains of Children With Autism Spectrum Disorder (ASD)
Written by Sasinathaya Aphichatphokhin
Edited by Kriti Iyer
January 5, 2023
Edited by Kriti Iyer
January 5, 2023
Reesearch
We often hear about the behavioral characteristics of autistic individuals, but seldom hear how these behaviors are associated with their brain structures. Autism spectrum disorders (ASD) are associated with brain structural changes that often impact an individual’s social interaction with others, and may cause an individual to develop repetitive and restricted behaviors or interests. Known causes of ASD include genetics, but there exist unknown environmental factors that researchers are still figuring out. This raises the question of how much of the brain structural changes are due to genetics, and how much is due to other unknown factors.
A neuroimaging study conducted in 2020 has found a relationship between autistic traits and brain folding patterns in 717 autistic children aged 6-9, however, the findings on the thickness of the outer layer of the brain - the cerebral cortex, are unclear in differences when comparing autistic children with neurotypical children (Amiri et al., 2020). Thus, to expand and make clear these findings, the same study was replicated in the year 2021, with 2,400 children aged 9-12. The goal of the study is to investigate the relationship between genetic factors and the brain structure of autistic children, as well as to investigate the extent to which the change in the brain structure of autistic children is associated with the autistic traits themselves. (Alemany et al., 2021).
The research findings demonstrated that children between the age of 9-12 with higher degrees of autistic traits have a smaller total brain volume and surface area in the inferior temporal and rostral middle frontal regions, and lesser thickness of the cerebral cortex in the superior frontal region.
The inferior temporal region of the brain is commonly known to be responsible for the visual recognition of objects. Thus, autistic children with lower surface areas in the inferior temporal region may experience varying degrees of difficulty in identifying and categorizing objects. Another region of the brain, the rostral middle frontal region, is known to be involved with our ability to plan, focus, and retain information, as well as the regulation of emotions and working memory. Thus, autistic children with lower surface areas in the rostral middle frontal region would experience varying degrees of difficulty focusing or completing tasks. Likewise, the superior frontal region of the brain, another region that experiences lower surface areas in autistic children, is also thought to be responsible for working memory and other cognitive functions.
Autistic children also experience a difference in brain folding patterns. During the third trimester of pregnancy, the brain of the fetus undergoes the most folding, which causes the brain’s outer layer to have a greater surface area to volume ratio, or in other words, it allows for more brain cells to fit into the limited space of the skull, thus enhancing the brain’s ability to process information. Research findings also demonstrated that children with higher degrees of autistic traits experience a lower degree of brain folding in the lateral occipital and the superior and inferior parietal lobes of the brain, which impacts their cognitive ability.
To investigate the degree to which genetics are associated with the brain structures responsible for autistic traits, researchers used the polygenic risk scores for ASD, which is an estimate of an individual’s genetic risk for ASD judged based upon the degree of delay in an individual’s gross motor skills, which is the ability to make whole body movement, combined with the degree of delay in language skills at the age of 18 months. The results concluded that the brain structural changes have less to do with genetic factors and that there exist unknown factors causing these brain structural changes associated with autistic traits. The results are also applicable to children of the general populace who may not be diagnosed with autism but share some autistic traits.
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