Cerebral Cortex Advance Access originally published online on June 13, 2006
Cerebral Cortex 2007 17(4):951-961; doi:10.1093/cercor/bhl006
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Functional and Anatomical Cortical Underconnectivity in Autism: Evidence from an fMRI Study of an Executive Function Task and Corpus Callosum Morphometry
1 Center for Cognitive Brain Imaging, Carnegie Mellon University, Pittsburgh, PA 15213, USA, 2 Departments of Psychiatry and Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
Address correspondence to Marcel Adam Just, Center for Cognitive Brain Imaging, Department of Psychology, Carnegie Mellon University, Pittsburgh, PA 15213, USA. Email: just{at}cmu.edu.
The brain activation of a group of high-functioning autistic participants was measured using functional magnetic resonance imaging during the performance of a Tower of London task, in comparison with a control group matched with respect to intelligent quotient, age, and gender. The 2 groups generally activated the same cortical areas to similar degrees. However, there were 3 indications of underconnectivity in the group with autism. First, the degree of synchronization (i.e., the functional connectivity or the correlation of the time series of the activation) between the frontal and parietal areas of activation was lower for the autistic than the control participants. Second, relevant parts of the corpus callosum, through which many of the bilaterally activated cortical areas communicate, were smaller in cross-sectional area in the autistic participants. Third, within the autism group but not within the control group, the size of the genu of the corpus callosum was correlated with frontalparietal functional connectivity. These findings suggest that the neural basis of altered cognition in autism entails a lower degree of integration of information across certain cortical areas resulting from reduced intracortical connectivity. The results add support to a new theory of cortical underconnectivity in autism, which posits a deficit in integration of information at the neural and cognitive levels.
Key Words: autism corpus callosum executive function fMRI functional connectivity
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