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2010-02-27 04:46:49
By Amanda Gardner
HealthDay Reporter by Amanda Gardner
healthday Reporter 1 hr 54 mins ago
FRIDAY, Feb. 26 (HealthDay News) -- It's not a particular brain region that
makes someone smart or not smart.
Nor is it the strength and speed of the connections throughout the brain or
such features as total brain volume.
Instead, new research shows, it's the connections between very specific areas
of the brain that determine intelligence and often, by extension, how well
someone does in life.
"General intelligence actually relies on a specific network inside the brain,
and this is the connections between the gray matter, or cell bodies, and the
white matter, or connecting fibers between neurons," said Jan Glascher, lead
author of a paper appearing in this week's issue of the Proceedings of the
National Academy of Sciences. "General intelligence relies on the connection
between the frontal and the parietal [situated behind the frontal] parts of the
brain."
The results weren't entirely unexpected, said Keith Young, vice chairman of
research in psychiatry and behavioral science at Texas A&M Health Science
Center College of Medicine in Temple, but "it is confirmation of the idea that
good communication between various parts of brain are very important for this
generalized intelligence."
General intelligence is an abstract notion developed in 1904 that has always
been somewhat controversial.
"People noticed a long time ago that, in general, people who are good
test-takers did well in a lot of different subjects," explained Young. "If
you're good in mathematics, you're also usually good in English. Researchers
came up with this idea that this represented a kind of overall intelligence."
"General intelligence is this notion that smart people tend to be smart across
all different kinds of domains," added Glascher, who is a postdoctoral fellow
in the department of humanities and social sciences at the California Institute
of Technology in Pasadena.
Hoping to learn more, the authors located 241 patients who had some sort of
brain lesion. They then diagrammed the location of their lesions and had them
take IQ tests.
"We took patients who had damaged parts of their brain, tested them on
intelligence to see where they were good and where they were bad, then we
correlated those scores across all the patients with the location of the brain
lesions," Glascher explained. "That way, you can highlight the areas that are
associated with reduced performance on these tests which, by the reverse
inference, means these areas are really important for general intelligence."
"These studies infer results based on the absence of brain tissue," added Paul
Sanberg, distinguished professor of neurosurgery and director of the University
of South Florida Center for Aging and Brain Repair in Tampa. "It allows them to
systemize and pinpoint areas important to intelligence."
Young said the findings echo what's come before. "The map they came up with was
what we expected and involves areas of the cortex we thought would be involved
-- the parietal and frontal cortex. They're important for language and
mathematics," he said.
In an earlier study, the same team of investigators found that this brain
network was also important for working memory, "the ability to hold a certain
number of items [in your mind]," Glascher said. "In the past, people have
associated general intelligence very strongly with enhanced working memory
capacity so there's a close theoretical connection with that."
More information
Learn more about the workings of the brain at Harvard University's Whole Brain
Atlas.