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UI researcher reports size differences in brains of autistic individuals
IOWA CITY, Iowa -- Among neurological disorders, autism is the new kid
on the block, and no one really knows what causes it.
For nearly 30 years scientists believed that autism was a disorder of
the mind, caused by poor parenting or perhaps early psychological trauma.
But, by the 1970s, it became clear that biological rather than psychological
factors cause the brain abnormality.
Today, psychiatrists still don't know exactly what that abnormality
is or where and how it develops. Those are questions Dr. Joseph Piven,
University of Iowa associate professor of psychiatry, and his colleagues
tackle daily. Recently, they found neuroanatomical differences between
the brains of autistic and healthy young adults.
These findings, published in the American Journal of Psychiatry and
the journal Neurology, show size differences in the corpus callosum
and cerebellum. Piven and his colleagues report that the middle and back
parts of the corpus callosum are smaller and the cerebellum is larger in
The corpus callosum is a large fiber pathway that runs through the brain
from front to back. It acts like a telecommunications network that allows
one side, or hemisphere, of the brain to "talk" to the other
side. The function of the cerebellum, once thought to mainly control movement,
is now believed to include coordination and integration of thought processes.
Rather than pointing to specific areas of the brain as the site of the
disorder, Piven views the size difference in the corpus callosum and cerebellum
as just two of many abnormal sites he suspects exist in the brain of autistic
individuals. The concept of multiple areas of the brain contributing to
autism is a relatively new one, but it makes sense in a disorder due to
abnormal brain development, Piven says.
"Earlier studies tried to localize the abnormality to a particular
part of the brain, but autism is a problem in the developing brain,"
Piven says. "Current studies indicate that we are not going to find
a single lesion to explain the complex range of deficits in autism,"
Piven believes that the presence of multiple brain abnormalities is
evidence of poor communication or connectivity throughout the brain and
leads to the problems associated with autism.
"The expected size relationships of various parts of the brain
to one another seems to be disproportionate or distorted in autism,"
he says. "I think this is part of an overall pattern showing that
different parts of the brain are out of sync with each other. This makes
you think that those areas might be disconnected functionally."
In the study, Piven used magnetic resonance imaging (MRI) to look at
and compare the autistic and healthy brains. It is basically neuroanatomy,
looking at brain structure rather than function, Piven says.
Little is known about the anatomy of the autistic brain and there is
still a lot to learn, Piven says. He plans to expand his research to include
functional imaging studies to help determine whether the structurally different
areas of the autistic brain are also functioning differently. He would
also like to examine the brains of autistic and healthy children over time
so he can look at developmental functional and structural changes in the
Piven and his colleagues are currently funded by the National Institutes
of Health to continue their structural neuroimaging studies of autism.