How gifted brains work
Posted May 4, 2005
Special to World Science
Highly intelligent people use slightly different brain circuitry to solve IQ test problems than their less gifted peers, some new studies have found.
The findings are sparking some debate, because different experiments have given different results, leading to different opinions on how highly intelligent brains work. Nonetheless, researchers say they’re hopeful that the findings have enough aspects in common to eventually give clear answers—and possibly, some speculate, help researchers devise techniques to improve thinking abilities.
“Where in the brain is intelligence? Are we getting close to an answer?” Richard J. Haier of the University of California at Irvine, who has conducted many studies on individual differences in intelligence, asked rhetorically. “I think we are.”
One new study has found that although people show increased activity in several brain
regions while taking IQ tests, gifted people show even greater activity in these regions.
This difference was especially pronounced in a zone called the posterior parietal cortex, at the top-back of the head, the researchers found, suggesting further study of this area might give insights into how intelligence works.
The researchers—Kun Ho Lee at Seoul National University in Korea, and others at Yale University in New Haven, Conn., and other institutions—published the findings in the Aug. 22 early online edition of the research journal
The posterior parietal cortex is considered important for “working memory”—the ability to hold items actively in mind, as when remembering a phone number for a few seconds, according to the researchers. Thus, high intelligence might partly be a fairly straightforward matter of more working memory capacity, the researchers said.
But the claim of a special role for this brain area was somewhat unusual in light of previous studies.
Of several past studies of highly intelligent people’s brain functions, most hadn’t suggested a special role for this region, though most did include it among several areas thought to be important for intelligence. However, at least one previous study did find a special role for this region, as Lee did. Also, Lee and colleagues noted, this area was enlarged in Einstein’s brain.
Nonetheless, Haier says the evidence overall doesn’t point to one brain area as having overarching importance in intelligence. “The idea that there is only one site for general intelligence has been proposed from time to time,” but the bulk of the evidence refutes it, he said.
The evidence does, however, point to a specific network of brain areas underlying intelligence, Haier said. Thus, this whole network could be studied to get a better understanding of intelligence.
Most of this network lies in the cerebral cortex, the wrinkly surface of the brain that has been considered the seat of most higher cognitive functions.
The network, he added, has been identified in over 20 imaging studies of both brain structure and function.
In structural studies, “we have found very specific brain areas where more gray matter goes with higher IQ,” he said. Gray matter refers to parts of the brain consisting mostly of the central bodies of brain cells, rather than their long, thread-like extensions, which they use to transmit signals to other cells. IQ stands for intelligence quotient, a measure of intellectual capacity as determined by an intelligence test.
The cerebral cortex areas Haier identifies as key for intelligence include parts of the parietal cortex—same region Lee and colleagues focused on—but also parts of areas known as the frontal, temporal and occipetal cortex. These have been tied to attention and goal-seeking behavior, language abilities, and visual information processing, respectively.
One variable that has confounded IQ-test studies is that some of them actually find lower, not higher, brain activation among gifted people. This fits neatly with a hypothesis proposed by Haier—that more intelligent brains work more efficiently, so that brain circuits unnecessary for the task at hand aren’t used. But the phenomenon has perplexed researchers on the whole, since some studies show the opposite.
Haier has proposed that the phenomenon may be related to how hard a task is for a particular person. Haier and colleagues in 1995 arranged a study so that gifted and average people are assigned problems that are equally difficult for their intelligence level, and found that the effect vanished.
Overall, the effect seems to reflect the fact that intelligent people have “more activity in less brain volume,” said Norbert Jaušovec of the University of Maribor in Maribor, Slovenia, in an email. But the effect is still not fully understood, he added; for instance, it seems more pronounced in males than in females.
Lee proposes that a better understanding of the biological basis of intelligence could help researchers devise techniques to improve learning abilities.
There’s no evidence that one can enhance intelligence as a whole, he said, but one might be able to stimulate activity in certain brain areas to enhance learning. In a recent email, he said he is interested in a device called the transcranial magnetic stimulator, which through the use of magnetic fields “may be able to activate specific regions of our brain.”
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