Brain Mapping Technology Discovers System Behind General Intelligence

A collaborative team of neuroscientists has mapped the brain structures that affect general intelligence.

The study, published the week of February 22, 2010, in the early edition of the Proceedings of the [U.S.] National Academy of Sciences (PNAS), adds new insights into determining what precisely is intelligence, and how can one measure it.

The research team from at the California Institute of Technology (Caltech; Pasadena, CA, USA), the University of Iowa (Iowa City, USA), the University of Southern California (USC; Los Angeles, USA), included Dr. Jan Gläscher, first author on the article and a postdoctoral fellow at Caltech, and Dr. Ralph Adolphs, a professor of psychology and neuroscience and professor of biology.

The Caltech scientists teamed up with researchers at the University of Iowa and USC to examine a uniquely large data set of 241 brain-lesion patients who all had taken IQ tests. The researchers mapped the location of each patient's lesion in their brains using voxel-based magnetic resonance imaging (MRI), and correlated that with each patient's IQ score to produce a map of the brain regions that influence intelligence.

"General intelligence, often referred to as Spearman's g-factor, has been a highly contentious concept,” said Dr. Adolphs. "But the basic idea underlying it is undisputed: on average, people's scores across many different kinds of tests are correlated. Some people just get generally high scores, whereas others get generally low scores. So it is an obvious next question to ask whether such a general ability might depend on specific brain regions.”

The researchers found that, rather than residing in a single structure, general intelligence is determined by a network of regions across both sides of the brain. "One of the main findings that really struck us was that there was a distributed system here. Several brain regions, and the connections between them, were what was most important to general intelligence,” explained Dr. Gläscher.

"It might have turned out that general intelligence doesn't depend on specific brain areas at all, and just has to do with how the whole brain functions,” added Dr. Adolphs. "But that's not what we found. In fact, the particular regions and connections we found are quite in line with an existing theory about intelligence called the ‘parieto-frontal integration theory.' It says that general intelligence depends on the brain's ability to integrate--to pull together--several different kinds of processing, such as working memory.”

The researchers reported that the findings create an avenue for further investigations about how the brain, intelligence, and environment all interact.

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California Institute of Technology
University of Iowa
University of Southern California