WEDNESDAY, Dec. 19, 2001 (HealthDayNews) -- No one knows exactly what causes autism, but researchers are zeroing in on some basic biological differences between autistic children and children who develop normally.
New research has found that young autistic children have larger brains than most kids. But bigger isn't necessarily better, because the autistic children were not able to recognize or react to changes in other people's emotions.
"These studies tell us that autism involves problems in very basic levels of social and emotional processing," says Geraldine Dawson, one of the researchers and the director of the University of Washington Autism Center.
The University of Washington researchers studied a group of about 50 children who were 3 and 4 years old. Some were autistic, some had developmental delays and others developed normally. The autistic children had varying levels of autistic symptoms, says Dawson.
One of the first things Dawson's colleague, Dr. Stephen Dager, a professor of psychiatry and radiology, noted was that the brains of the autistic children were about 10 percent larger than those of normal or developmentally delayed children, according to Dawson.
At birth, all of the children's heads measured a normal size, so something happened between birth and age 3 in the autistic children to accelerate the growth of their brains, she says.
Using a special type of magnetic resonance imaging, Dager also discovered that one portion of the brain, the amygdala, was disproportionately larger in autistic children. The amygdala is a part of the brain used for emotional processing, particularly for picking up cues on people's emotions, according to Dawson. It is located in the lobes on either side of the brain behind the temples.
"This finding is intriguing because we know autism involves problems connecting with people's emotions," says Dawson.
Dawson's team wanted to see how well autistic children would react to pictures of people showing different emotional expressions.
After being fitted with sensors that monitored their brain activity, the children were shown two pictures. One was of a woman with a neutral expression. The other showed the woman with a frightened expression.
Dawson says the researchers chose the fear expression for two reasons.
The first is that the amygdala is sensitive to picking up on fear. From research on normally developing children, it is known that by the age of 7 months, babies show a different reaction to a fear face than to a neutral one. Dawson says this response probably developed during evolution because it would be important to be able to respond if another member of your species was showing fear.
However, she says, the children with autism had no difference in brain activity when shown the two pictures, while the normally developing children showed a larger brain response when they saw the fear picture.
"This suggests that at a very basic level . . . these children are not really interpreting or responding to emotional cues in a normal way," Dawson says. "Some pretty basic brain systems are disrupted."
Knowing this could lead to better and earlier intervention programs, she adds. "If at 10 to 12 months, a baby is not responding, it would alert us that we should be checking the child for autism," she says. And early intervention is important because the earlier treatment starts, the more chance there is to rewire the developing brain, she adds.
The findings of these studies were presented early last month at the first International Meeting for Autism Research, which was part of the annual meeting for the Society for Neuroscience.
"This is an extremely important area of investigation," says Dr. Eric London, vice president of medical affairs for the National Alliance for Autism Research.
"There could be a very discreet biological system involved in facial recognition," London adds, and if this is the case, there could end up being a relatively simple biological treatment for it when researchers discover exactly what's going wrong in the autistic brain.
What to Do: If you'd like to know more about autism, read this article from Kid's Health, or this one from the Autism Society of America.
