Mommy Brain: It's Not What You Think

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Mommy brains are actually bigger than before a woman gives birth, suggests research.

THE GIST

- Good news for new moms: Parts of your brain actually grow after birth.

- Post-partum brain changes give moms the motivation to take care of their babies.

- The findings could eventually help women who fail to bond with their babies after birth.

New moms may feel their brain cells dying with every cumulative hour of sleep loss. But a new study offers hope.

In the first months after giving birth, the study found, parts of a mother's brain may actually grow. Even better news, doting mamas who gushed the most about how special and perfect their babies were showed the most growth.

The parts of the brain that grew are involved in motivation, reward behavior and emotion regulation. That suggests that, by reshaping itself, the post-partum brain motivates a mother to take care of her baby, and then feel happy and rewarded when she does.

The findings may eventually help women who feel disconnected from their babies or even hostile toward them in the early months, said lead author Pilyoung Kim, a developmental psychologist, now at the National Institutes of Mental Health in Bethesda, Md.

"We could maybe compare brain changes in mothers who were depressed or had problems bonding with their infants to normal mothers," said Kim, who was at Yale University when she did the work. "And we might be able to develop some kind of intervention programs to help mothers feel more rewarded about their parenting and their baby."

During pregnancy and the post-partum period, women often feel their brains turning to mush. New moms report that they have trouble remembering things that they used to remember easily. It's such a common phenomenon that women often call it "Mommy Brain." Some research has even shown that women's brains shrink slightly during pregnancy.

But studies in mice, rats, and other mammals have shown growth and other physical changes in the brains of new mothers. These changes appear to prepare the animals for their new roles. And the mothers' brains remain altered for the rest of their lives.

To see if the similar changes might happen in people, Kim and colleagues scanned the brains of 19 mothers a few weeks after giving birth and again three to four months later. Their results, published in the journal Behavioral Neuroscience, showed a small but significant amount of growth in a number of brain regions, including the hypothalamus, prefrontal cortex and amygdala.

These are the areas that motivate a mother to take care of her baby, feel rewarded when the baby smiles at her, and fill her with positive emotions from simple interactions with her infant. These brain areas are also involved in planning and foresight, which might help a mother anticipate her infant's needs and be prepared to meet them.

In other words, basic changes in the brain might explain the unconditional love, constant worrying and snack-packing habits that many people call a "maternal instinct."

The researchers speculate that pregnancy hormones prime the brain to be open to reshaping when a newborn arrives. And while it's not yet clear whether changes in a mother's brain stimulate her to care for her child, or whether caring for a child changes the brain, the study showed a clear relationship. What's more, mothers who talked most positively about their babies underwent the biggest changes.

There are good genetic reasons why having a baby might re-sculpt a woman's brain for the benefit of her baby, said Craig Kinsley, a neuroscientist at the University of Richmond in Virginia. A mother passes her genes to her children, after all, and she'll do what it takes to keep them alive. (Some studies suggest that the brains of fathers might undergo similar changes, too).

In one of his own studies, Kinsley found that, compared to virgin rats, mother rats were much faster at learning where to find food in a maze. In nature, that might mean that moms are quicker to find food and return to their nests, allowing them to both feed their little ones and protect them from predators.

"From an evolutionary standpoint, a mother is faced with a really significant challenge," Kinsley said. "She had to do everything she did before, plus a whole new suite of behaviors to keep her offspring alive. How females evolved in nature is to have their brains adapt in pregnancy, so that their young enhance their behaviors."

As for the complete loss of memories for names, trivia and other ordinary things that come with giving birth, the brains of new moms may simply have new priorities.

"We are clearly showing that mothers have better memories about things related to their infants," said Kim, who has a four-month old of her own. "There are a lot of things going on, and mothers might feel forgetful about things that are not related to their infants. It's just dependent on what is really important for us to remember at the time."