Key Deficiencies In Brains of People With Autism
In a pair of groundbreaking studies, brain scientists at Carnegie Mellon University and the University of Pittsburgh have discovered that the anatomical differences that characterize the brains of people with autism are related to the way those brains process information.
Previous studies have demonstrated a lower degree of synchronization among activated brain areas in people with autism, as well as smaller size of the corpus callosum, the white matter that acts as cables to wire the parts of the brain together. This latest research shows for the first time that the abnormality in synchronization is related to the abnormality in the cabling. The results suggest that the connectivity among brain areas is among the central problems in autism. The researchers have also found that people with autism rely heavily on the parts of the brain that deal with imagery, even when completing tasks that would not normally call for visualization.
"Human thought is a network property. You think not with one brain area at a time, but with a network of collaborating brain areas, with emphasis on collaborating. In autism, the network connectivity (the bandwidth) through which the areas communicate with each other may be limited, particularly in the connections to the frontal cortex, limiting what types of networks can be used," said Marcel Just, co-author of the studies and director of Carnegie Mellon's Center for Cognitive Brain Imaging.
Both studies focused on people with autism who have normal IQs. In one study, the researchers used functional magnetic resonance imaging (fMRI) to view which parts of the brain were activated in people with autism compared to a control group of normal participants while completing the Tower of London task. In a Tower of London task, participants must - in a set number of moves - rearrange the positions of three distinctive balls in three suspended pool pockets to match a specified pattern. This requires a person to strategize and plan several moves ahead.
The experiment confirmed the authors' previous findings that people with autism suffer from a lack of synchronization among brain regions, which helps to explain why some people with autism have normal or even superior skills in some areas, while many other types of thinking are disordered. In addition, their findings particularly implicate the lower synchronization between the frontal cortex and other portions of the brain. They have discovered that key portions of the corpus callosum seem to play a role in the limitation on synchronization. In people with autism, anatomical connectivity -- based on the size of the white matter - was found to be positively correlated with functional connectivity, which is the synchronization of the active brain regions. They also found that the functional connectivity was lower in those participants in whom the autism was more severe. The study will be published in the journal Cerebral Cortex.
The second study, to be published in the journal Brain, examined a long-standing belief, supported through scientific research as well as anecdotal accounts, that people with autism rely heavily on visualization to process information. Temple Grandin, a professor at Colorado State University who has autism, says in her autobiography "Thinking in Pictures" that "Words are like a second language to me.