The scientists analyzed 25 genes in post-mortem brain tissue of children with and without autism. These included genes that serve as biomarkers for brain cell types in different layers of the cortex, genes implicated in autism and several control genes.

Their findings are published in the online edition of the New England Journal of Medicine. The researchers analyzed the six layers of the cortex for any abnormalities in the early development of these brain cells in each specific cortical layer.

The study found that in the brains of children with autism, key genetic markers were absent in brain cells in multiple layers. According to the scientists this defect indicates that the crucial early developmental step of creating six distinct layers with specific types of brain cells -- something that begins in prenatal life -- had been disrupted.

The lack of such genetic markers greatly affects the frontal cortex and the temporal cortex of the brain. While the frontal cortex is associated with higher-order brain function, such as complex communication and comprehension of social cues, temporal cortex is associated with language. The disruptions of frontal and temporal cortical layers seen in the study may underlie symptoms most often displayed in autistic spectrum disorders.

Since the defects occur in patches, the study supports the notion that the brains of young, autistic children can rewire connections to make up for the losses in early development. It also explains why toddlers diagnosed with autism show immediate improvement upon early treatment.

(JPN)

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