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Public release date: 4-Nov-2001


Contact: Dan Page
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University of California - Los Angeles

UCLA team maps how genes affect brain structure, intelligence;
dramatic images shed light on brain diseases, personality differences

UCLA brain mapping researchers have created the first images to show
how an individual's genes influence their brain structure and
intelligence.

The findings, published in the Nov. 5 issue of the journal Nature
Neuroscience, offer exciting new insight about how parents pass on
personality traits and cognitive abilities, and how brain diseases
run in families.

The team found that the amount of gray matter in the frontal parts of
the brain is determined by the genetic make-up of an individual's
parents, and strongly correlates with that individual's cognitive
ability, as measured by intelligence test scores.

More importantly, these are the first images to uncover how normal
genetic differences influence brain structure and intelligence.

Brain regions controlling language and reading skills were virtually
identical in identical twins, who share exactly the same genes, while
siblings showed only 60 percent of the normal brain differences.

This tight structural similarity in the brains of family members
helps explain why brain diseases, including schizophrenia and some
types of dementia, run in families.

"We were stunned to see that the amount of gray matter in frontal
brain regions was strongly inherited, and also predicted an
individual's IQ score," said Paul Thompson, the study's chief
investigator and an assistant professor of neurology at the UCLA
Laboratory of Neuro Imaging.

"The brain's language areas were also extremely similar in family
members. Brain regions that were found to be most similar in family
members may be especially vulnerable to diseases that run in
families, including some forms of psychosis and dementia."

The scientists employed magnetic resonance imaging technology to scan
a group of 20 identical twins, whose genes are identical, and 20
same-sex fraternal twins, who share half their genes.

Using a high-speed supercomputer, they created color-coded images
showing which parts of the brain are determined by our genetic
make-up, and which are more adaptable to environmental factors, such
as learning and stress.

To create the maps of genetic influences on the brain, the UCLA
scientists teamed up with the National Public Health Institute of
Finland, and the Finnish Universities of Helsinki and Oulu.

In a national initiative, the Finnish team tracked all the same-sex
twins born in Finland between 1940 and 1957 - 9,500 pairs of twins -
many of whom received brain scans and cognitive tests.

Their genetic similarity was confirmed by analyzing 78 different
genetic markers. These individual pieces of DNA match exactly in
identical twins, and half of them match in siblings.

Recent research has shown that many cognitive skills are surprisingly
heritable, with strong genetic influences on verbal and spatial
abilities, reaction times, and even some personality qualities,
including emotional reactions to stress.

These genetic relationships persist even after statistical
adjustments are made for shared family environments, which tend to
make members of the same family more similar. Until this study,
little was known about how much individual genotype accounts for the
wide variations among individual brains, as well as individual's
cognitive ability.

The UCLA researchers are also applying this new genetic brain mapping
approach to relatives of schizophrenic patients, and individuals at
genetic risk for Alzheimer's disease, to screen them for early brain
changes, and help understand familial risk for inherited brain
disorders where specific risk genes are unknown.

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Other UCLA researchers involved in the project are Tyrone Cannon, a
professor of psychiatry and biobehavioral and human genetics, and
Arthur Toga, professor of neurology and director of the UCLA
Laboratory of Neuro Imaging.

Images from the study are available online for viewing or downloading
at http://www.loni.ucla.edu/~thompson/MEDIA/NN/IMAGES/
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Jose Morales Ph.D.