Autistic preschoolers have larger-than-normal brains, can't distinguish emotions from facial photographs

December 04, 2001

Preschool-age children with autism exhibit no difference in brain activity when they are shown photographs of faces displaying different emotions, and their brains are larger than normal, according to new research at the University of Washington's Autism Center.

The findings were reported at the first International Meeting for Autism Research in San Diego last month by Geraldine Dawson, director of the UW Autism Center and a professor of psychology, and Stephen Dager, UW professor of psychiatry and radiology. The autism meeting was held in conjunction with the annual meeting of the Society for Neuroscience.

Both studies used the same pool of 3- and 4-year-old autistic, developmentally delayed and normally developing children. In Dawson's study, the children wore bonnets studded with 64 sensors that monitored brain activity. The children were shown photographs depicting fear and a neutral expression. The brains of normally developing and developmentally delayed children exhibited different activity depending on the picture being viewed. However, the brain activity of the autistic children remained the same when the different pictures were shown.

Dawson said that normally developing infants will notice their mothers' facial expressions and emotions in the first six months of life and that they are able to recognize emotions from facial expressions by age 7 months. A region of the brain called the amygdala that is associated with emotions seems to be a center for recognizing and reacting to fear.

"The ability to react to fear is either innate in humans or develops very early in life," she said. "It is a selective advantage for our brains to be able to pick up fear, an ability that comes from our early human ancestors.

"Children with autism do not appear to be able to pick up facial signals and notice other people's emotions. They can't read the signals or facial expressions of emotions in a normal way. This tells us the problem with the brain likely emerges very early and involves very basic brain systems, those responsible for encoding emotions."

Understanding this deficit in reading facial expressions and noticing emotions should help parents understand the behavior of their autistic child and why the child doesn't respond with empathy for others, according to Dawson.

"It also points to the importance of interventions, such as behavioral interventions that reward children for paying attention to facial cues. Computer programs are being developed at the UW that help children pay attention to proper cues and teach them what facial signals mean," she said.

New research at the UW Autism Center is finding out how much impact early intervention programs have with these recognition systems and whether they can help rewire the brain to process faces and emotions more normally. Dager's work found that the amygdala is disproportionately larger in preschool autistic children than in normally developing and mentally retarded youngsters.

"We looked both at brain structure and brain chemistry, using a specialized form of magnetic resonance imaging called PEPSI, or Proton Echo Planar Spectroscopic Imaging, that was developed at the UW," Dager said. "We measured the volumes of different regions of the brain and found that the kids with autism had about 10 percent bigger brains on average."

Dager added that both boys and girls with autism exhibited increased brain volume, in comparison to normally developing children of the same gender. Typically human males have larger brains than females, but Dager says that bigger is not necessarily better.

"Additional studies that we are conducting measuring brain chemistry suggest that the brain cellular composition is altered in the autistic children. This is potentially a very important finding, although we are still trying to better understand the functional significance of these abnormalities," Dager said.

He said it's puzzling that this region of the brain that is so closely involved with the normal expression of emotion should be enlarged in this particular group of children who have difficulty expressing normal emotional engagement.

Dager and his colleagues also are trying to determine what enlargement of the amygdala means in relationship to the clinical course or prognosis of autism and how brain developmental processes these children undergo as they grow older affect their brain chemistry. The children are being studied at ages 6 and 9 to evaluate the progression of these brain structural and chemical findings.

Dager cautions that enlargement of the amygdala or of the brain in general cannot be used as a diagnostic tool to determine if a child has autism.
For more information, contact Dawson at (206) 543-1051 or; Dager at (206) 616-1558 or

University of Washington

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