SEATTLE--Babies who later develop autism have abnormal brain circuitry almost from birth, which keeps them from recognizing faces and developing normal social skills, according to new research presented here 14 February at the annual AAAS meeting. The findings could help doctors diagnose early warning signs of the disease in babies and give them the intensive early therapy that might help them grow into healthy children.
Babies headed toward autism lack the fundamental building blocks of social skills: They ignore human faces and voices, even their mother's, and they fail to make eye contact with or imitate adults. But when toddlers with those warning signs are given intensive training--25 hours a week--on how to recognize faces, among other skills, then one in four is normal by kindergarten.
To investigate what goes wrong in the autistic brain, Geraldine Dawson and Elizabeth Aylward of the University of Washington (UW) Autism Center and their colleagues compared brain activity of autistic and normal adolescents and adults while they examined pictures of human faces or cars. Using functional magnetic resonance imaging, the researchers found that a brain region called the fusiform gyrus became active in healthy but not autistic subjects when they viewed human faces. Instead, the inferior temporal lobe lit up in autistic subjects. This area was active when normal subjects viewed pictures of cars, suggesting that the autistic subjects' brains are lumping faces together with inanimate objects. However, autistic adults did use their fusiform gyrus to recognize pictures of their own mothers, which hints that autistic people could be trained to recognize faces and overcome some of their disabilities.
In another brain-imaging study at the UW Autism Center, psychiatrist Stephen Dager and his colleagues showed that autistic brains were physically different from those of normal children. Dager's team used a technique called magnetic resonance spectroscopy to examine the size of various brain regions and the levels of several brain chemicals. Autistic children had proportionally larger amygdalas than normal children--and the larger the amygdala, the slower the child learned social skills. What's more, by tracking the movements of brain chemicals, they deduced that neurons in autistic brains were less tightly packed and more disorganized.
Finding early signs of autism "is a big thing," says molecular geneticist Joseph Buxbaum of Mt. Sinai School of Medicine in New York City. Understanding how the developing brain goes awry will help researchers find genes that contribute to the disease, Buxbaum says. And knowing the genes involved, together with the brain differences, could lead to earlier diagnoses and treatments.