The researchers noted that the factor most closely associated with the areas showing the greatest volume increase is when the axons in those areas myelinate, a key step in maturation that allows nerve impulses to be transmitted properly. In both autistic and DLD patients, the most enlarged areas were those that myelinate latest in normal development and where myelination takes a longer period of time.
"Knowing that white matter is most enlarged in the area that develops myelin latest will help us narrow the time window in which to look for the cause of these problems and should help focus future research," says Martha Herbert, MD, PhD, of MGH Neurology and the Center for Morphometric Analysis, the paper's lead author.
Autism is a serious developmental disorder characterized by a lack of normal social interaction, language abnormalities and repetitive, ritualistic behavior. Many earlier studies have shown that autistic children often have unusually large brains and experience rapid brain growth in the first years of life. This increased brain volume appears to be concentrated in the white matter. Primarily made up of axons long processes that extend out from brain or other nerve cells the white matter is located in the interior of the brain, beneath the cerebral cortex which contains the bodies of brain cells.
The same white matter abnormality is found in
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Contact: Julie Bergan
jbergan@partners.org
617-726-0274
Massachusetts General Hospital
22-Mar-2004