Autism is not associated with any single deficit in the brain.
Instead, the neural bases of autism are likely to lie in the brain’s connections and pathways.
Primary research methodologies employed in the search for neural associates of autism are neuroimaging, post-mortem analysis, and animal models. Collectively, these techniques have focused on potential abnormalities in the cerebellum, frontal cortex, hippocampus, and amygdala. Autism has also been linked to irregularities in neurotransmission, particularly in the GABA-A receptor, serotonin and acetylcholine. There is also evidence that overall brain size is increased in some individuals with autism.
Neuroimaging using functional Magnetic Resonance Imagery (fMRI) suggests that the fusiform “face area” in the temporal lobe may be impaired in people with autistic disorder. This is interesting, because this area of the brain is associated with face recognition (or emotional expression) – autistic individuals often have profound difficulties in recognizing even very basic facial expressions.