Autism is associated with underconnectivity between hemispheres and an overabundance of local connections; the neuronal pruning that helps the average brain avoid overload does not appear to occur in autism. Many autistic children are born with smaller heads than the norm, but by six to fourteen months, many have larger heads than the norm. The brains of autistic children are often enlarged by 10 or 15 percent, a condition that appears to resolve as the children grow. The human brain consists of grey matter, where thought is generated, and white matter, which conveys that thought from one area
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