Genes play role in amount of brain's 'gray matter'
NEW YORK, Nov 05 (Reuters Health) - Genetics may play a role in the amount of gray matter a person has, and by extension, how intelligent they are, a team of researchers reports.
"The idea of this study is to see how much an individual's genetic makeup influences brain structure and intelligence," lead author Dr. Paul M. Thompson, assistant professor of neurology at the University of California, Los Angeles, told Reuters Health.
US researchers collaborated with researchers in Finland and used MRI scans to compare the brain matter of 20 identical twins and 20 fraternal twins using a Finnish database of twins. The findings were released in the advance online publication of Nature Neuroscience, and will be published in the December issue.
The investigators found that the amount of gray matter, a measure of the density of brain cells found in the outer layer of the cortex where information is processed, seemed to be highly determined by genetics. The amount was much more similar among identical twins, who share 100% of their genes, than fraternal twins, who only share half.
"The frontal cortex and language cortex were very strongly determined by genetics," Thompson said. "Those areas were almost indistinguishable in identical twins." The frontal cortex is associated with problem solving and IQ, while the language cortex is associated with speech production and language comprehension, he noted.
These results begin to explain why patterns of intelligence seem to run in families, he suggested. "The puzzle was, people knew some features of intelligence were inherited, but no one knows why that is," he said. "This builds a bridge between those two observations. It's somewhat controversial, that the genes are the agents of change in the brain."
The similarity in brain matter amongst relatives may also explain why diseases such as Alzheimer's and dementia run in families, he pointed out.
"It isn't a depressing result," he added. "It doesn't mean to say we can't alter IQ. Basically, it just means the brain's structure is a certain way to begin with, but every time you learn, you make new brain connections."
SOURCE: Nature Neuroscience online 2001;10.1038.
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