This past year we have completed several behavioral and brain imaging studies of social perception and social communication in adolescents with Autism Spectrum Disorders (ASD). Our behavioral studies have confirmed that adolescents with ASD have difficulty perceiving specific emotional states from faces. They also have poor memory for faces relative to other objects. This memory deficit was found to be largely due to abnormal eye movements during encoding. Specifically, the ASD subjects tend to make fewer fixations when scanning faces but not other objects they are attempting to remember. This reduced scanning was, in turn, correlated with poor subsequent memory performance. Consistent with these behavioral findings, our brain imaging data suggest that although the face-processing network in ASD individuals responds appropriately to faces, this system is not utilized normally for more complex processing tasks. For example, whereas normally developing individuals engaged the face-processing network when performing tasks that require understanding of social interactions, the ASD subjects do not. Rather these subjects engage this network regardless of whether the task requires understanding of social or mechanical interactions. One interpretation of these findings is that ASD may be characterized by deficient functional neural connectivity within specific nodes of this processing network. Our on-going studies of brain functional connectivity support this possibility. In collaboration with the NIMH Scientific and Statistical Computing Core, we have developed an unbiased, data-driven, procedure for identifying brain regions showing abnormal patterns of functional connectivity in one group of subjects versus another. These analyses have identified several regions of the ASD brain that show abnormally sparse connections with other brain regions. These regions include the ventromedial portion of prefrontal cortex, the amygdala, the anterior and posterior temporal lobes and other locations known to be involved in social cognitive processes. Detailed analyses of structural brain differences have revealed abnormal, age-related cortical thinning in ASD in several of these same brain regions.
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