Download Study: Possible Prenatal Causes of Autism (November 9, 2011)

STUDY SHOWS PRE-BIRTH BRAIN GROWTH PROBLEMS LINKED TO AUTISM
Children with autism
(http://www.nimh.nih.gov/health/topics/autism-spectrum-disorders-pervasi
ve-developmental-disorders/index.shtml) have more brain cells and
heavier brains compared to typically developing children, according to
researchers partly funded by the National Institutes of Health.
Published in the Journal of the American Medical Association on Nov. 9,
2011, the small, preliminary study provides direct evidence for possible
prenatal causes of autism.
"Earlier studies of head circumference and early brain overgrowth have
pointed us in this direction, but there have been few quantitative
neuroanatomical studies due to the lack of post-mortem tissue from
children with autism," said Thomas R. Insel, M.D., director of the
National Institute of Mental Health (NIMH), part of NIH. "These new
results, along with an earlier study[1] reporting altered wiring of the
prefrontal cortex, focus our attention on this critical area of the
brain in autism."
The prefrontal cortex is involved in various higher order functions such
as language and communication, social behavior, mood, and attention.
Children who have autism tend to show deficits in such functions.
Eric Courchesne, Ph.D., of the University of San Diego School of
Medicine Autism Center of
Excellence(http://www.nimh.nih.gov/science-news/2007/nih-funds-new-progr
am-to-investigate-causes-and-treatment-of-autism.shtml), and colleagues
conducted direct counts of brain cells in specific regions of the
prefrontal cortex in postmortem brains of seven boys who had autism and
six typically developing males, ranging in age from 2-16 years. Most
participants had died in accidents, but the researchers did not base
their selection on causes of death.
To assist in this task, the researchers used a computerized tissue
analysis system developed by co-investigator and NIMH grantee Peter
Mouton, Ph.D., of the University of South Florida, Tampa, and
colleagues.
The researchers found that children with autism had 67 percent more
neurons in the prefrontal cortex and heavier brains for their age
compared to typically developing children. Since these neurons are
produced before birth, the study's findings suggest that faulty prenatal
cell birth or maintenance may be involved in the development of autism.
Another possible factor that may contribute to the neuronal excess is a
reduction in apoptosis, or programmed cell death, which normally occurs
during the third trimester and early postnatal life.
Though small, this preliminary study examined all relevant postmortem
tissue available at the time. The relative scarcity of tissue from very
young children may limit future research as well, but efforts to include
a larger number of samples are needed to confirm these findings and to
identify patterns of age-related changes in autism.
----------------------REFERENCE:
Courchesne E, Mouton PR, Calhoun ME, Semendeferi K, Ahrens-Barbeau C,
Hallet MJ, Barnes CC, Pierce K. Neuron Number and Size in Prefrontal
Cortex of Children with Autism. JAMA. 2011 Nov 9;306(18).
----------------------1. Zikopoulos B, Barbas H. Changes in prefrontal axons may disrupt the
network in autism(http://www.ncbi.nlm.nih.gov/pubmed/21048117). J
Neurosci. 2010 Nov 3;30(44):14595-609. PubMed PMID: 21048117; PubMed
Central PMCID: PMC3073590.
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This NIH News Release is available online at:
<http://www.nih.gov/news/health/nov2011/nimh-08.htm>.