Autism Brains Have Too Many Neurons, Study Suggests

Children with autism have an abnormally large number of neurons in the prefrontal cortex (PFC), a brain region important for abstract thinking, planning and social behaviors, according to a study published yesterday in the Journal of the American Medical Association.Because of the study's small sample size, however, and the complexities of analyzing postmortem brains, many researchers caution against interpreting the results as relevant for all children with autism.In the study, researchers analyzed postmortem brain tissue from two areas of the PFC from seven boys with autism and six controls, ranging in age from 2 to 16 years. In the brains from the children with autism, the dorsolateral PFC, which comprises the outer layers of the region, holds 79 percent more neurons, and the mesial PFC, encompassing deeper tissue, holds 29 percent more neurons compared with controls, the study found.According to lead investigator Eric Courchesne, the study provides a cellular explanation for imaging studies showing brain overgrowth in children with the disorder."Now for first time, in my opinion, there’s a fairly robust and specific pathology that can be used in animal model studies and cellular studies to test speculations about genetic and non-genetic factors that could cause this disorder," says Courchesne, professor of neurosciences at the University of California, San Diego.Other experts are skeptical of the results, however, saying they may not represent the wider population of children with autism."I would emphasize that this study is very preliminary. Only seven individuals with autism were included and it’s just one region," says Nicholas Lange, associate professor of psychiatry and biostatistics at Harvard University, who wrote a commentary of the study in the same issue of the journal."My overwhelming feeling is that not too much should be made of this at this point," says David Amaral, director of research at the University of California, Davis MIND Institute. "It would be premature to draw any conclusions until the study has had an independent replication using a much larger number of brains."Read more at...SFARI, November 2011.