Men and boys with autism have fewer neurons in the amygdala, a part of the brain involved in emotion and memory
The team at the University of California, Davis, looked at the brains of nine autistic men and boys, aged 10 to 44, and compared them to 10 brains of males who did not have autism.
They counted the number of neurons to see whether the brain cells were smaller or fewer in number.
Writing in the Journal of Neuroscience, David Amaral, research director of the UC Davis Medical Investigation of Neurodevelopmental Disorders Institute, and former graduate student Cynthia Mills Schumann said they found significantly fewer neurons in the brains of the people with autism.
"One possibility is that there are always fewer neurons in the amygdala of people with autism. Another possibility is that a degenerative process occurs later in life and leads to neuron loss. More studies are needed to refine our findings," Schumann said in a statement.
In May, the U.S. Centers for Disease Control and Prevention found that up to one in every 175 U.S. children has autism, a disease that can cause symptoms ranging from social isolation to repetitive and damaging behaviors and sometimes mental retardation.
"While we have known that autism is a developmental brain disorder, where, how and when the autistic brain develops abnormally has been a mystery," Dr. Thomas Insel, director of the National Institute of Mental Health, which funded the study, said in a statement.
"This new finding is important because it demonstrates that the structure of the amygdala is abnormal in autism. Along with other findings on the abnormal function of the amygdala, research is beginning to narrow the search for the brain basis of autism."
Neurologists believe the amygdala is important in autism because it generates appropriate emotional responses and helps the brain process memories that are key to social learning.
"We're in the very early stages of understanding autism and its neurological pathologies. It's clearly a process with many steps, and at least we are now one step further," Amaral said.
UC Davis M.I.N.D. Institute researchers find fewer neurons in the amygdala of males with autism
New Autism Study Shows Discrepancy in Brains
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