Autism spectrum disorders (ASD) are a group of behaviorally defined neurodevelopmental disorders.  Studies have consistently found that the brains of autistic children are larger than neurotypical children.  Abnormalities have also been found in the cerebellum, cerebral cortex and the limbic system (hippocampus, amygdala, cingulate gyrus, and septal nuclei)

Never heard of these brain structures?  For an interactive tour of the brain, PBS’s “The Secret Life of the Brain” offers a 3D look inside the brain and discusses its various structures.

Though there are abnormalities in the brains of ASD children, there are complex interactions between the brain and the rest of the body, particularly the gut and the immune system.  Much research discusses the benefits of addressing gut issues to improve the neurological symptoms of ASD.

Two excellent books that discuss the autistic brain are:
Jepson’s Changing the Course of Autism
Coleman’s The Neurology of Autism