PITTSBURGH -- Using functional magnetic resonance imaging (fMRI) scans, a team of scientists at Carnegie Mellon University and the University of Pittsburgh have found differences in the activation and synchronization of brain networks between people with autism and those without it. These findings could yield strategies for treating autism, a mysterious brain disorder that impairs verbal and non-verbal communications and social interactions. The study will be published in the journal Neuroimage and will be available online November 29 at www.sciencedirect.com.
The research was conducted at Carnegie Mellon's Center for Cognitive Brain Imaging (CCBI) and was co-authored by Marcel Just, director of the center and the D.O. Hebb Professor of Psychology at Carnegie Mellon. The lead author was Hideya Koshino, an assistant professor of psychology at California State University at San Bernardino and a former postdoctoral fellow at the CCBI.
The study follows on the heels of groundbreaking research published by the CCBI in July that proposed the underconnectivity theory, which holds that autism is a system-wide brain disorder that limits the coordination and integration among brain areas. Because this type of coordination is critical to complex thinking and social interaction, a wide range of behaviors are affected in autism.
The current study compared a group of high-functioning adults with autism to a control group of normal participants with similar ages and IQs. Each participant saw a series of alphabet letters presented one at a time at the center of a computer screen, and they had to decide if the letter was the same as the previous letter, or in some cases, whether it was the same as the letter that was presented two letters previously. Although the two groups performed the task equally well, the fMRI scans revealed three important differences in brain activation between them. First, the autism group showed more activation in the right hemisphere of the brain than the left, whereas the control group showed more activation in the left hemisphere than the right. The left hemisphere usually is associated with processing verbal information and the right hemisphere is associated with visual and spatial information processing. Since letters can be interpreted as verbal codes (letter names) or visual codes (letter shapes), the different uses of two hemispheres seem to correspond to a difference in strategies: The autism group likely remembered letters by their shape, while the control group remembered letter names.
A second difference was that the autism group showed less activation in the anterior parts (prefrontal regions) of the brain and more activation in the posterior parts than the control group. Working memory is usually associated with the prefrontal regions of the brain, and the control group showed a typical pattern of activation in the prefrontal regions, whereas the autism group showed weaker activation in the prefrontal regions. This pattern is consistent with previous findings in which people with autism group showed more activation in the posterior language area (Wernicke's area) than the anterior language area (Broca's area) during sentence comprehension.
The third difference was that the overall synchronization among the brain regions was weaker for the autism group than for the control group. The activated brain areas were also not as tightly organized into groups with similar synchronization in the case of the people with autism. The results were consistent with the underconnectivity theory. Taken together, the results of these and other autism studies suggest that possible treatments of autism might include instruction and training that focuses on the integration of the types of processing performed by different brain areas.
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