10 Facts about a Woman's Brain - Part 3

By Robin Nixon LiveScience.com Staff Writer

Despite the trumpets of women's lib, science suggests sex differences are innate. Women, apparently, are not curvy versions of men sporting high-heeled shoes.

Here is Part 3 of the 10 things every man should know about women's brains.

 7. She is affected by pregnant brain

Progesterone increases 30-fold in the first eight weeks of pregnancy, causing most women to become very sedated, Brizendine said. "Progesterone is a great sleeping pill."

A woman's brain also shrinks during pregnancy, becoming about 4-percent smaller by the time she delivers, according to a 2002 study published in the American Journal of Neuroradiology. (Don't worry; it returns to normal size by six months after delivery.)

Whether pregnancy causes women to think differently is controversial -- one recent study linked memory problems to pregnancy hormones -- but some researchers have suggested the changes prepare brain circuits that guide maternal behavior.

These circuits likely continue to develop after birth. Handling a baby releases maternal hormones, even among females who have never been pregnant, found researchers at Tufts University. While measured in rats, the finding offers a chemical understanding of the bonding that can occur among foster moms and children.

The study was published in the journal Developmental Psychobiology in 2004.

 8. She is affected by mommy brain

The physical, hormonal, emotional and social changes facing a woman directly after giving birth can be monumental. "And because everything else has changed, she needs everything else to be as predictable as possible, including the husband," Brizendine said.

Over the course of evolution, it was rare for our maternal ancestors to be full-time mothers, said Brizendine, because there was always kin-folk around to help with child rearing. And a mother needs a lot of support, not only for her own sake but for the child's as well. Her ability to adequately respond to her infant can impact the child's developing nervous system and temperament, research shows.

One way Mother Nature tries to help is through breastfeeding. Nursing may help women deal with some types of stress, studies suggest. (Too much stress, however, can disrupt lactation.) One study even found that breastfeeding might be more rewarding to the female brain than cocaine. The research was published in the Journal of Neuroscience in 2005.

 9. She goes through adolescence twice

No one wants to go through adolescence again. Its physical changes and hormonal fluctuations not only create mood swings and physical discomfort but nagging questions about self-identity as well.

Women, however, lucky girls, get to do just that. They go through a "second adolescence" called perimenopause in their 40s. It starts around age 43 and reaches its pinnacle by 47 or 48 years old. (Men's hormones also change as they age, but not nearly as abruptly.) In addition to erratic periods and night sweats, a woman's hormones during this transition are so crazed she can be as moody as a teenager.

The duration of perimenopause varies from two to nine years, with most women leaving it behind by age 52.

10. She loves risk during the mature years

Once The Change has finished, and the body moves into its "advanced" stage, the female brain gets a second wind. While men start to show increased interest in relationships as they age, the mature woman becomes ready to risk conflict - especially if her nest is now empty.

She may continue to feel motivated to help others, but her focus might shift from her immediate family to local and global communities. She may also feel a strong desire to do more for herself, and her career, after decades of care-taking, explains Brizendine.