Bigger doesn't mean better … men have more brain cells than women, but researchers aren't saying more brain power

0 Comments | Insight on the News, Sept 8, 1997 | by Joyce Price

Danish researchers have discovered that men, on average, have 4 billion more brain cells than women. But they are stumped as to what men do with them.

The researchers, led by Bente Pakkenberg, a neurologist at Kommune Hospital in Copenhagen, examined the brains of 94 adult corpses -- 62 males and 32 females -- who ranged in age from 18 to 93. The average age for men was 52; for women, 64.

"We started this study 10 years ago, and we collected brain cells from the whole country," says Pakkenberg. "We excluded anyone with any diseases of the central nervous system, as well as anyone who was an alcoholic or who used drugs or anyone who had cancer that had metastasized."

Using what Pakkenberg described as a "new quantitative method" that employed a statistical model, an ordinary microscope and a television screen, she and her colleagues counted the number of neurons found in the cortex of the brain of each of the cadavers. "This new technique allowed us to move down through the [brain] tissue and count in 3-D," explains Pakkenberg. The cortex, the outer layer of brain matter, controls many of the higher nerve centers. "It's the part of the brain that has to do with abstract thinking with fantasizing with speech.... Most of the cortex is dedicated to higher brain function."

The result? The average number of brain cells in men was 23 billion, while the female average was about 19 billion. "There was a 16 percent difference in the count -- almost 4 billion fewer nerve cells in women than in men" says Pakkenberg, whose findings were reported in the Journal of Comparative Neurology. "That really surprised me." She says it's also well-recognized that male brains are heavier than those of females.

Pakkenberg admits she's battled about what the findings mean. "Right now, it's a mystery," she says. "The knowledge we already have shows men are not smarter than women.... The average IQ score comes out the same in males and females."

But Marc Nuwer, professor of neurology at the University of California at Los Angeles School of Medicine, notes that scientists long have known that the brain functions differently in men and women. According to Nuwer, subtle differences in the shape of the temporal lobes of male and female brains may be a reason men are more spatial and women more verbal.

Nuwer expressed surprise that men have 16 percent more brain cells than women. "I wouldn't say it isn't so, but I'd have to see other studies" that confirm it. He suggested that different counts in the frontal cortex, the area of the brain responsible for judgment and insight, would be more important that differences in the motor cortex, which controls voluntary movement. Higher male cell counts in that region could be influenced by the "muscle bulk of men"' says Nuwer.

Pakkenberg and her colleagues are continuing their research but, for now, she sees no reason for concern about the shortfall of nerve cells in female brains. "Maybe we'll find it's much more important how they are connected than how many there are," she says. And if men have to have 4 billion more brain cells to function as normally as women, it's all right with me."