A new study led by a team of UCLA scientists has found that changes in the brains of people with autism spectrum disorder (ASD) are more widespread than previously thought. The study, published in Nature, found that nearly every region of the cortex is changed in some way in people with ASD, contrary to the prevailing belief that only certain areas of the brain are affected by ASD. These findings could redefine our current understanding of how autism spectrum disorder progresses at the molecular level and could guide future autism spectrum disorder research and treatments.
Autism Spectrum Disorder Pathology
Autism spectrum disorder (ASD) is considered a neurological and developmental disorder. Although it is regarded as “developmental” because symptoms often begin in early childhood, ASD can be diagnosed at any age. Presentation and severity of symptoms exist on a wide spectrum, but “autism spectrum disorder” generally refers to a group of neurodevelopmental abnormalities that present via broad impairments in communication, learning, behavior, and social interaction.
Unlike neurodegenerative diseases like Parkinson’s and Alzheimer’s disease, there has not previously been a clear understanding of ASD’s pathology at a molecular level. But a new study recently published in Nature may change that.
Refining Our Understanding of Autism Spectrum Disorder
In this new study, a team from UCLA utilized an RNA sequencing technique to compare gene expression in postmortem brain tissue samples from individuals with ASD and neurotypical controls. The team looked at cortical tissue samples from 11 different brain regions, including higher critical association regions involved in functions such as reasoning, language, social cognition, and mental flexibility, as well as primary sensory regions. In doing so, the researchers found that individuals with ASD had brain-wide changes in virtually all of the 11 evaluated cortical regions. In fact, the individuals with ASD had hundreds of genes with altered expression in nearly every cortical region analyzed.
Importantly, the changes were not limited to genes known to be associated with ASD. Rather, they were spread throughout the cortex, regardless of whether the cortical regions were higher critical association regions or primary sensory regions. The changes in the primary sensory regions were particularly surprising, as it has previously been believed that ASD primarily affects higher-order cognitive functions.
While changes were found in every region, the most significant differences were found in the visual cortex and parietal cortex, a region that processes touch, pain, and temperature. Researchers theorize this may be linked to different forms of sensory hypersensitivity, which is a hallmark of many people diagnosed with ASD.
Implications for Future Treatment Options
The findings suggest that ASD is an even more complex and comprehensive disorder than previously understood, with disruptions occurring along many different neural pathways. It is possible that the changes seen in primary sensory regions play a role in the social and behavioral symptoms seen in ASD. Indeed, this could explain why current treatments for ASD — which typically target a single gene or pathway — have had limited success. If this theory proves to be true, future treatments for ASD may need to target a wider array of neural pathways to be effective.
More research will be needed to confirm this theory and to understand the implications of the UCLA team’s results, but these initial findings could represent a promising shift in our understanding of how ASD progresses at the molecular level.
As study author Dr. Daniel Geschwind, the Gordon and Virginia MacDonald Distinguished Professor of Human Genetics, Neurology and Psychiatry at UCLA, explains, “We now finally are beginning to get a picture of the state of the brain, at the molecular level … in individuals who had a diagnosis of autism. This provides us with a molecular pathology, which similar to other brain disorders such as Parkinson’s, Alzheimer’s and stroke, provides a key starting point for understanding the disorder’s mechanisms, which will inform and accelerate development of disease-altering therapies.”
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