Autism is a term that covers a wide range, or "spectrum," of social impairments, communication disorders and abnormally repetitive patterns of behavior. The Centers for Disease Control estimates that the disorder is found in 1-in-110 children. It is caused by the improper development of the nervous system, primarily the brain. In recent years, medical imaging technology has allowed researchers to safely compare the brains of children with autism to those without the disorder. Thus, there has been progress in understanding exactly which areas of the brain are linked to autism.
Processing faces, emotions
For instance, researchers at the University of North Carolina at Chapel Hill last year used magnetic resonance imaging to view the brains of 50 toddlers with autism and 33 without autism. They found the children with autism were more likely to have an enlarged amygdala--a small, almond-shaped brain structure responsible for many functions, including the processing of facial expressions and determining the emotional significance of events.
The researchers, who published their findings in the Archives of General Psychiatry, noted that scientists have known for many years that children with autism had larger brains, but there was still mystery about exactly which portions of the brain become enlarged.
Other areas of brain involvement
Though a recent finding focused on the amygdala, the researchers said the cause of autism was likely much more complex, and linked to the malfunction of many brain systems. Thus, the study was not conclusive, but did strongly suggest a link between autism and an enlarged amygdala in toddlers.
Meanwhile, researchers are studying other parts of the brain and finding connections to autism. The work is complicated because the brains of autistic people change dramatically over time, making it difficult to develop a definitive test to diagnose the disorder or pinpoint what is causing it.
"Monkey-see, monkey-do"
In 2007, researchers at the Fay J. Lindner Center for Autism, North Shore-Long Island Jewish Health System in Bethpage, N.Y., used a new, high-technology method of mapping the brains of children diagnosed with autism, and found these children had more gray matter in their brains than children without the disorder.The researchers noted that the increase in gray matter occurred throughout brains of children with autism, but was more pronounced in the parietal lobe, an area of the brain behind the frontal lobe.
The parietal lobe of the brain processes sensory information, and contains mirror neurons, sometimes called "monkey-see, monkey-do" cells. In essence, these cells allow us to unconsciously learn things such as facial expressions by watching someone else.
One disorder, or many?
Complicating the issue further is continuing debate within the medical community about whether autism disorder spectrum is one disorder or a compilation of distinct disorders.
For instance, in 2008 an international group of researchers published work in The Journal of Child Psychology and Psychiatry finding that there was significant difference in the brains of children diagnosed with Asperger's syndrome--a form of autism marked by normal language development--and children diagnosed with another form of autism.
Overall, the children with Asperger's syndrome had significantly more gray matter in their brains, and showed other brain abnormalities not found in the other children with autism.
More to learn
So there are many unanswered questions about autism and the brain. The federal government considers autism to be an urgent public health concern because of its increasing prevalence, and is promoting more research into the disorder's causes, risk factors, signs and symptoms.
A 2010 report by the U.S. Department of Health and Human Services noted that there has been a "massive surge" in research funding for autism, and future efforts should include more research on adults and on people with autism who are unable to speak. Also, the report noted, a better foundation for research is needed, including repositories for biological specimens and better surveillance.
