Changes in the Autistic Brain

Excess neurons may be responsible for autism

(RxWiki News) Children with autism generally have head and brain overgrowth that is larger than the development of children without autism. Several brain regions involved in cognition, communication and social skills show dysfunction early in life for autistics.

New research shows that they also exhibit an abnormal number of neurons, in addition to larger than average brain weight.

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Eric Courchesne, Ph.D., of the NIH-UCSD School of Medicine led a small, preliminary study of 13 postmortem male children, 2 to 16 years old, to examine a possible relationship between this larger brain growth and possible excess neurons. The seven children with autism had an average of 67 percent more prefrontal brain neurons than the six control subjects without autism.

The differences in neurons between the children were statistically significant. The average DL-PFC count in the autistic children was 1.57 billion neurons compared with an average of 0.88 billion neurons in control children. The average M-PFC count in the autistic group was 0.36 billion neurons compared with an average of 0.28 billion neurons in controls.

The brain weight of the autistic children also deviated from the normal weight for age by 17.6 percent. "Because cortical neurons are generated in prenatal, not postnatal life, pathological overabundance of neurons indicates early developmental disturbances in molecular and genetic mechanisms that govern proliferation, cell cycle regulation, and apoptosis," the study authors wrote. "Therefore, knowledge of the neural basis of overgrowth could point to early causal mechanisms in autism and elucidate the neural functional defects that engender autistic symptoms."

The researchers caution that the small population in the study means that the results are not from a large enough sample to statistically examine the relationship. Future studies could reveal important connections between neuron counts and autism, as well as other intellectual disability.

The findings were publishing in the November 2011 issue of the The Journal of the American Medical Association.

Review Date: 
November 10, 2011