The amygdala is a small structure that is part of the brain and is involved in interpreting the social and emotional meaning of sensory information, such as recognizing the different emotions on the faces of others, or interpreting images of our environment that inform us about potential dangers, and thus generate a response at a physiological or behavioral level. This element, so important for our survival, has historically been related to the difficulties with social behavior that people with an autism spectrum disorder (ASD) present.
It has long been known that school-age children with autism have an abnormally large amygdala, but until now it was unknown exactly when this abnormal growth occurred, a mystery that has just been revealed by a new study by scientists at The University of North Carolina at Chapel Hill (UNC), which has shown for the first time that this excessive growth begins in the first year of life of the baby, when he is between six and 12 months old, before the moment in which the characteristic symptoms of the autism; a finding that would help diagnose ASD early.
The researchers used magnetic resonance imaging to show that the amygdala enlarges too rapidly in childhood and when this overgrowth begins. They found that increased amygdala growth in infants later diagnosed with autism differed significantly from brain growth patterns in infants with Fragile X syndrome, another neurodevelopmental disorder where no differences in amygdala growth were observed.
The research, which has been published in the American Journal of Psychiatry – the official journal of the American Psychiatric Association – has shown that while babies with fragile X syndrome already suffer from cognitive delays at six months of age, those who will later be diagnosed with autism do not present any deficit in cognitive ability at that age, but experience a progressive reduction in cognitive ability between six and 24 months, the age at which they were diagnosed with autism spectrum disorder in this study.
“An optimal time to start interventions and help children who are most likely to develop autism may be during the first year of life.”
At six months, the babies who later developed autism still did not show differences in the size of their amygdala, but it began to grow faster from that age and up to 12 months, when it becomes significantly larger. “We also found that the rate of amygdala overgrowth in the first year is related to the child’s social deficits at age two,” said Mark Shen, assistant professor of psychiatry and neuroscience at UNC Chapel Hill and faculty at the Carolina Institute. . for Developmental Disabilities (CIDD) and first author of the study, who adds: “The faster the amygdala grew in childhood, the more social difficulties the child showed when he was diagnosed with autism a year later.”
Identify children at risk of autism in the first year of life
The study was conducted through The Infant Brain Imaging Study (IBIS), a consortium of 10 universities in the United States and Canada, and its authors enrolled a total of 408 infants, including 58 infants most likely of developing autism because they had an older brother with autism, and who were later diagnosed with autism, 212 other babies who were more likely to have autism but did not develop it, 109 typically developing controls, and 29 babies with Fragile X syndrome. More than 1,000 natural sleep MRIs were performed at six, 12, and 24 months of age.
Previous research by this same team and others had shown that although the difficulties in social relationships typical of autism are not present when children are six months old, at that age those who are later diagnosed with autism do have difficulties with the way they communicate. that pay attention to visual stimuli in their environment, so researchers have hypothesized that these early problems with processing visual and sensory information may put increased stress on the amygdala, leading to its overgrowth .
In fact, amygdala overgrowth has been linked to chronic stress in studies of mental disorders such as depression and anxiety, and may provide a clue to better understanding this observation in babies who later develop autism.
Dr. Joseph Piven, professor of psychiatry and pediatrics at the University of North Carolina at Chapel Hill and lead author concludes: “Our research suggests that an optimal time to start interventions to help children who are most likely to develop autism can be during the first year of life. A presymptomatic intervention approach could improve visual and other sensory processing in infants even before social symptoms appear.”
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