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Date: May 14, 2008
Autism Study Links Repetitive Behavior Patterns to Brain Function Differences
Hofstra psychology professor part of study scheduled to appear in major psychiatry journalHofstra University, Hempstead, NY – Individuals with autism who exhibit repetitive behavior show reduced activity in brain regions normally responsible for attention and executive function, the processes that help organize our actions and behaviors, researchers at Hofstra, Duke, and the University of North Carolina report in the current issue of the journal Biological Psychiatry.
These results their study, scheduled to run in the May 15, 2008 issue of Biological Psychiatry, suggest that the repetitive behavior patterns observed in individuals with autism may be associated with dysfunction within the brain’s attentional and executive response circuitry.
"During a test of cognitive flexibility in which participants were asked to alter behavioral responses and shift cognitive sets, individuals with autism showed impaired performance and decreased activation in several areas of the brain compared with typically-developing individuals," said first author Keith Shafritz, Ph.D., assistant professor of psychology at Hofstra University. "This pattern of reduced brain activity appeared in all participants in our autism group."
The study used functional magnetic resonance imaging (fMRI) to determine brain regions that became active during the cognitive task, or a task that required perception and reasoning. The researchers found that participants with autism had less activation in regions of the prefrontal cortex, parietal cortex, and basal ganglia than a group of typically-developing participants. These brain regions are associated with attentional and executive mental processes, which help people to act flexibly during changing environmental demands, Dr. Shafritz said.
Autism is characterized by deficits in social interactions and communication skills, and the appearance of restricted, repetitive, and stereotyped behavior patterns. While the brain mechanisms in people with autism that account for their problems with social interactions have been well-studied using brain imaging, not much is known about possible brain mechanisms underlying repetitive behaviors in autism. "This is one of the few studies that used a test of executive function rather than a test of social or emotional awareness," said Dr. Shafritz. "It is also the first study to combine two distinct elements of executive function into a single cognitive test to study cognitive and behavioral flexibility in autism using fMRI technology."
The study included 18 individuals with autism and 15 typically-developing individuals. While in the MRI, the participants were shown individual images of geometric shapes, and were instructed to press one response button for most of the shapes, but a different response button for a specified target shape. The target shape changed periodically during the test in order to determine how well participants could alter their cognitive representations of the response rules.
Although individuals with autism had intact ability to represent the task rules even when they changed, these participants had difficulty altering ongoing response patterns when presented with a target shape. It was during these response shifting trials that the participants with autism showed reduced brain activity.
Other authors on the study included Aysenil Belger, Gabriel Dichter, and Grace Baranek from both Duke University and the University of North Carolina – Chapel Hill.
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