Thursday, April 28, 2005

Understanding the Connectivity Theory and Autism

There are many lines of evidence that many of the cognitive and behavioral difficulties associated with autism are due changes in the connectivity of brain areas. As a result, children or adults with autism have problems with activities that require the coordination of multiple brain areas (imagery) or flexible understanding (multiple representations) or spoken language.

In this paper from Stanford, the discussion is on "underconnectivity", but "overconnectivity" occurs in other systems resulting in overlod or hypersensitivities. From the paper:"The underconnectivity framework can account for the social symptoms of autism. Social interactions place large (if not the largest) demands on information integration. This model attributes social abnormalities in autism to a deficit in integrative processing. Abnormalities may arise in integrating the perceptual and affective processing of social stimuli such as face affect and prosody with language iwht the concurrent theory of mind processing to determine the social partner's intentions."

In the figures below, see the difference in the extent of brain activation with sentence comprehension. Also, when many brain areas are compared, high function autistic subjects had much lower levels of connectivity, at least as measured by activation on fMRI.

An interesting side note was that autistic subjects appeared able to answer sentence comprehension questions more rapidly, though less accurately especially when sentence structure was more demanding. More errors were noted with passive voice sentences like: "The editor was saved by the secretary" than "The cook thanked the father."

Underconnectivity and Autism (pdf file)

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