April 12, 2012
Brain Injury Subjects Used To Map General Intelligence

While you can find people who (quite erroneously) deny the importance or existence of general intelligence the research that establishes the existence of Charles Spearman's 'g' is really quite good. In the latest development Vietnam vets who have very localized brain damage were used to the areas of the brain key for enabling general intelligence.

CHAMPAIGN, Ill. Scientists report that they have mapped the physical architecture of intelligence in the brain. Theirs is one of the largest and most comprehensive analyses so far of the brain structures vital to general intelligence and to specific aspects of intellectual functioning, such as verbal comprehension and working memory.

Their study, published in Brain: A Journal of Neurology, is unique in that it enlisted an extraordinary pool of volunteer participants: 182 Vietnam veterans with highly localized brain damage from penetrating head injuries.

Having patients with very localized damage was key to identifying which parts of the brain are most important for determining general intelligence.

"It's a significant challenge to find patients (for research) who have brain damage, and even further, it's very hard to find patients who have focal brain damage," said University of Illinois neuroscience professor Aron Barbey, who led the study. Brain damage from stroke, for example often impairs multiple brain areas, he said, complicating the task of identifying the cognitive contributions of specific brain structures.

But the very focal brain injuries analyzed in the study allowed the researchers "to draw inferences about how specific brain structures are necessary for performance," Barbey said. "By studying how damage to particular brain regions produces specific forms of cognitive impairment, we can map the architecture of the mind, identifying brain structures that are critically important for specific intellectual abilities."

Brain CT scans were essential to identify where general intelligence is located. Turns out to be a fairly small number of areas of the brain.

The researchers took CT scans of the participants' brains and administered an extensive battery of cognitive tests. They pooled the CT data to produce a collective map of the cortex, which they divided into more than 3,000 three-dimensional units called voxels. By analyzing multiple patients with damage to a particular voxel or cluster of voxels and comparing their cognitive abilities with those of patients in whom the same structures were intact, the researchers were able to identify brain regions essential to specific cognitive functions, and those structures that contribute significantly to intelligence.

"We found that general intelligence depends on a remarkably circumscribed neural system," Barbey said. "Several brain regions, and the connections between them, were most important for general intelligence."

Where your general smarts come from:

These structures are located primarily within the left prefrontal cortex (behind the forehead), left temporal cortex (behind the ear) and left parietal cortex (at the top rear of the head) and in "white matter association tracts" that connect them.

What will be interesting: discovery of genes expressed during development in those regions and genetic variations that influence how much those genes get expressed. Note that since neuron generation continues well into adolescence the mutations of interest might be for making the brain grow more rather late in development.

Share |      Randall Parker, 2012 April 12 09:51 PM  Brain Intelligence

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