New research reveals that children with autism have an overabundance of nerve cells in a brain region involved in social, emotional, communication and reasoning skills. The finding furthers understanding of the differences in brain “wiring” that give rise to autism’s core symptoms.
 
The research also helps narrow the search for autism’s genetic and environmental causes, says lead researcher, Eric Courchesne, Ph.D., of the University of California, San Diego’s Autism Center of Excellence School. In particular, it points to events occurring before birth, when nerve cells in this brain region—the prefrontal cortex—arise and are then partially pruned away, he explains.
 
The study, published today in the Journal of the American Medical Association, was co-funded by Autism Speaks and relied on brain donations made to its Autism Tissue Program (ATP).
 
“Tissue-based research has the ability to literally transform our understanding of autism, its causes, and inform direction for treatment development,” comments Robert Ring, Ph.D., Autism Speaks vice president of translational research.
 
Courchesne and his colleagues counted nerve cells in the prefrontal cortex of seven post-mortem brain samples from children with autism. They compared these with cell counts from brain samples of six children who did not have autism. Those with autism averaged 67 percent more nerve cells, or neurons, in this brain region. The children ranged in age from 2 to 16 years at the time of death.
 
Ten years ago, Courchesne first associated early brain overgrowth with autism based on magnetic resonance imaging (MRI) of more than a hundred children ages 2 to 16. “However insights into the cellular nature of the overgrowth can only be done through direct examination of brain tissue donated after death,” he explains.
 
Another clue emerging from the study was the finding that the excess of nerve cells in the prefrontal cortex of children with autism is out of proportion with a more modest increase in overall brain weight.  This means that the overlarge brain size long associated with autism actually underestimates the degree of excess nerve cells in the crucial prefrontal region.
 
This, in turn, suggests profound differences in brain cell interconnections—both within the prefrontal cortex and between this brain region and other parts of the brain, Courchesne notes.
 
With further research, a better understanding of these altered connections may provide insights into the nature of autism’s symptoms and how to relieve them. It might also help identify measures that might decrease risk during crucial periods of early brain development.
 
A parent-supported program of Autism Speaks, the Autism Tissue Program is dedicated to furthering scientific understanding of autism, autism related disorders and the human brain. It makes brain tissue available to as many qualified scientists as possible to advance autism research and unravel the mysteries of this and related neurological conditions.
 
“We truly appreciate the generosity and partnership of parents who donate to the Autism Tissue Program and help further understanding of the biological basis of autism,” says Autism Speaks Chief Science Officer Geri Dawson, Ph.D. “This research will not only help us understand the causes of autism but also lead to new treatments.”
 
For more information on family registration please visit the ATP website.
 
--Reported by Autism Speaks science writer Madeleine Johnson