By Serena Gordon, HealthScoutNews
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
"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
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
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
"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.
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