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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 autistic individuals.

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," he says.

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 brain.

Piven and his colleagues are currently funded by the National Institutes of Health to continue their structural neuroimaging studies of autism.