Forget the "decade of the brain": it’s becoming evident that the modern fascination with neuroscience is not going away anytime this century. The fact is, thanks to the neurobiological revolution, nothing is what it used to be. Including motherhood.

In this vein Katherine Ellison, author of The Mommy Brain: How Motherhood Makes Us Smarter (2005), brought welcome news to mothers everywhere: Having babies doesn’t zap a woman’s brain cells after all.

In fact, scientists say, childbirth and motherhood, like many other challenging experiences, actually increase brain cells and along with these little darlings (the new brain cells as well as the babies) come increased skills of all kinds.

At the center of this good news is the now-familiar concept neurogenesis: the brain’s ability to grow and change as it develops new neurons. This amazing plasticity is encouraged by repeated new actions, especially of the "positive, emotionally charged, and challenging" variety scientists call "enrichment."

As it happens, childbearing, beginning with pregnancy, is enrichment’s mother lode. Challenging new experiences borne of daily interaction with our children strengthen much more than our multitasking skills. Functional magnetic resonance imaging (fMRI) reveals increases in a host of areas, including (but not limited to) emotional intelligence, sensory powers, mental perception, motivation, attention, problem solving, prioritizing, memory and learning. And the gains are not temporary. In fact, indications are that these changes last for the rest of our lives�"long past the time our grandchildren are born.

So why have women almost universally embraced the idea that having children turns their brains to jelly?

Sleep deprivation certainly plays a role, but Ellison points to neuroscientists whose findings add other crucial pieces to the puzzle. "What’s really going on," she translates, is that "a pregnant and early postpartum woman’s brain is tied up in a major, hormone-powered transition." In other words, our bodies have just served us a powerful hormonal cocktail designed to prepare us for unprecedented growth and reorganization. "Motherhood," says Ellison, "just like puberty, may knock us off our feet for a time, only to set us back up, often stronger than before." Comparing the forgetfulness of pregnant mothers to Einstein’s famous distractedness, Ellison nevertheless qualifies the analogy: "Encouraging as this paradigm may be . . . it’s important to remember that new mothers are coping with some serious physical challenges that Albert Einstein could barely have imagined."

Despite the role of pregnancy-induced hormones in this brain-enriching experience, the good news is not only for mothers. Adoptive parents and other caregivers also reap some of the brain-boosting benefits of child-rearing and experience some physiological changes. This is especially true for fathers.

"If research on mice has any bearing on humans," says Ellison, "modern, engaged dads may be gaining some of the same advantages from parenthood as have been found in maternal rats. The key appears to be the degree of involvement with the children." Further, Ellison documents the rise of certain "parenting" hormones in men when their wives are pregnant, and the well-known phenomenon called Couvades syndrome, in which "sympathy morning sickness" and "sympathy weight gain" are factors.

But are these pre-baby changes only "sympathetic" in fathers? A 2006 study by the University of Wisconsin�"Madison suggests that there is more to it. In the first nonhuman primate study into this phenomenon, researchers concluded: "It is clear that expectant fathers of these species are physiologically responsive to their mate’s pregnancy and the impending birth. Males need to be prepared to engage in infant care immediately after birth and this requires carrying multiple infants weighing up to 20 percent of their adult body weight. Both the hormonal and the physical weight change suggest that marmoset and tamarin males prepare for the demands of infant care."

If, as scientists speculate, these changes come about through the exchange of pheromones between pregnant mothers and fathers, it may be one more benefit to be gained from ensuring close family ties.

Ellison’s thoughtful collection of research dispatches the sometimes popular notion that raising a child is "less worthy" work for thinking people. In fact, it’s beginning to look like one of the best avenues for increasing human potential.

Perhaps motherhood, after all, is its own reward.