Women, Men, and PETs

The 1990s have been dubbed "the decade of the brain," and it is true that remarkable advances have been made by the neurosciences in discovering how the brain operates. Several recent studies suggest that the operation of men's and women's brains may differ in significant ways.

For example, Ruben Gur and his colleagues at the University of Pennsylvania recorded PET scans of men and women who were asked to think of nothing in particular. That is, the research participants were instructed to relax and let their brains idle as they exerted as little mental effort as possible. The researchers found that for most participants the task was difficult to complete; PET scans revealed that these idle minds nonetheless hummed with activity. The locus of that activity, however, differed across the sexes. Men's brains often showed activity in the limbic system, whereas women often showed activity in the posterior cyngulate gyrus. The meaning of these differences is difficult to interpret; the difficulty is compounded by the 13 men and 4 women who showed patterns of activity characteristic of their opposite sex peers. As an early peek into the brain, however, they hint that the centers of activity for "blank" brains differ for women and men.

In a separate study, researchers at the University of California, Irvine, asked 22 men and 22 women to solve SAT math problem while undergoing a PET scan. Half of each group had SAT math scores above 700, whereas the other half had scores below 540. The temporal lobes of the 700+ men showed heightened activity during the math task, although this was not true for the women; the 700+ women's temporal lobes were no more intensively used than those of the 540-group women. Richard Haier, who helped lead the study, speculates that women in the top group might be using their brains more efficiently than women in the average-scoring group. More generally, although both men and women did well at the task, their brains were operating differently to accomplish it.

Ruben and Raquel Gur also studied men's and women's brains in response to emotional expressions. Shown pictures of either happy or sad faces, both men and women were quite adept at spotting happiness. Women, however, could identify sadness about 90% of the time, regardless of whether it was on the face of a man or a woman. By comparison, men were accurate in spotting sadness 90% of the time on a man's face, but only 70% of the time if the expression was posed by a woman. Once again, PET scans revealed that women's brains didn't have to work as hard at this task as did men's; in fact, women's limbic systems were less active than the limbic systems of the poor-scoring men.

There are a number of other differences between women's and men's brains. Women tend to have a larger corpus callosum than men, for example. Women may have a higher concentration of neurons in their cortexes than men, for another. But the meaning behind these differences is a matter far from decided.

Begley, S. (1995, March 27). Gray matters. Newsweek, pp. 48-54.