While neither men nor women may be the more intelligent sex, their brains may take different paths to reach the same intellectual level, according to one team of researchers.

Their study found that among men and women who performed equally on intelligence tests, women had far more intelligence-related white matter in their brains than men did, while men surpassed women when it came to intelligence-related gray matter.

Gray matter can be seen as the brain's "information processing centers," whereas white matter is like the wiring connecting those centers, said Dr. Richard J. Haier, a professor of psychology at the University of California, Irvine, and the study's lead author.

The findings suggest that women and men may have "fundamentally different brain architectures" underlying intelligence. "It has nothing to do with men being more intelligent than women, or women being more intelligent than men," Haier said.

Instead, according to the researcher, men and women may draw upon different brain designs to arrive at the same intellectual capacity. That possibility is of more than a scientific interest, Haier noted; it could help researchers better understand sex differences in stroke and degenerative brain diseases like Alzheimer's disease.

The study, published online January 16, 2005 in the journal NeuroImage, involved 48 men and women between 18 and 84 years old who took a standard battery of IQ tests and had MRI brain scans to gauge the volume of white and gray matter in different brain areas related to intelligence.

Overall, the researchers found, men and women performed equally on the IQ tests. However, the brain structures involved in intelligence appeared distinct.

Compared with women, men had more than six times the amount of intelligence-related gray matter, while women had about nine times more white matter involved in intelligence than men did.

In addition, women had a large proportion of their IQ-related brain matter -- both white and gray -- concentrated in the brain's frontal lobes, a region at the front of the brain involved in movement, emotions and higher functions such as speech, reasoning and judgment.

Men, on the other hand, had 90 percent of their IQ-related gray matter distributed equally between the frontal lobes and the parietal lobes -- a region right behind the frontal lobes involved in sensory perception, such as taste and touch, and skills, such as reading and math.

In addition, the large majority of the men's IQ-related white matter -- 82 percent -- was found to dwell in a third brain region, the temporal lobes. These lobes govern functions such as perceiving sound and processing memories.

According to Haier, the fact that women's IQ-related brain matter was more centralized in the frontal lobes may help explain why strokes affecting this brain area appear to inflict more damage in women than men.

Whether the different brain designs translate into differences in specific intellectual skills, like math or language, is unknown. It's possible, according to Haier, that the findings offer one explanation for the stereotypical male predilection for numbers and spatial questions and female preference for language.

But, as he pointed out, that's a complex and controversial issue.

Earlier this month, Harvard University president Lawrence Summers caused a stir when he suggested that "innate differences" between men and women could be one reason women are underrepresented in the upper strata of the science and engineering fields.

When it comes to sex differences found in the brain, though, the degree to which they are inborn is not necessarily clear. As Haier and his colleagues note in their report, there is evidence that the volume of the brain's gray matter can increase with learning, and therefore may be a matter of environment as well as genes.

SOURCE: NeuroImage, online January 16, 2005.