How Motherhood Changes the Brain

LiveScience.com

Chocolate treats and sentimental cards may sweeten mom's belly and heart this Mother's Day, but it turns out motherhood also goes right to the noggin, with plenty of research showing how having kids, and even the process of childbirth, can change a mama's brain.

Recent research has revealed some of the changes that take place in women's brains during motherhood, and experts say that understanding how a mom’s brain works could help them figure out what motivates moms to care for their babies.

"With this research, we hope to better understand how to support moms who don't naturally experience a brain reward response when they interact with their baby," said Dr. Lane Strathearn, a developmental pediatrician at Baylor College of Medicine in Houston, Texas.

In the future, this field of study could lead to treatments that help women with mental illnesses or who lack certain types of normal brain responses. "We're currently researching whether giving moms oxytocin, a hormone that triggers a reward response in the brain, could influence their response to their child," Strathearn said.

After birth, the brain grows

The changes seem to begin the moment the baby is born. For instance, in a 2010 study, researchers looked at brain-scan images of 19 women before and after they gave birth and found that the size of mothers' brains increased shortly after childbirth.

"We observed small but significant increases in the volume of gray matter in the brain," said study co-author Pilyoung Kim, a developmental psychologist who performed the research at Yale University.

Kim and colleagues also found that moms who gushed over their babies a month after childbirth showed the greatest growth in parts of the brain, compared with moms who didn't respond as enthusiastically.

The period directly after childbirth is an important time for new moms. According to the researchers, moms develop sensitive mothering skills during this time, and changes to the brain may be linked with how these skills develop.

The researchers observed increases in gray matter in brain areas such as the hypothalamus, amygdala, parietal lobe and prefrontal cortex. These regions are responsible for emotion, reasoning and judgment, the senses and reward behavior.

Compared with the less-enthusiastic moms, the awestruck moms were more likely to develop bigger mid-brains, and saw growth in key regions linked to maternal motivation, rewards and the regulation of emotions, Kim's team found.  

The researchers said this expansion in the brain's "motivation" area might lead to more nurturing, which in turn could help babies thrive. Still, "we don't know whether it's the experience that changes the brain, or the brain that changes the experience," said Kim, who is now with the National Institute of Mental Health.

While it remains unclear exactly why the brain grows, the researchers said it might be that an increase in hormones — including estrogen, oxytocin and prolactin — play a role.

Pleasure at the root of mommy behavior

Experts believe maternal behavior may be fostered by a pleasure system in the brain that involves areas such as the substantia nigra, which creates dopamine, a chemical messenger that interacts with certain brain cells and causes a "feel-good" high.

Once the brain receives these "feel-good" signals, moms, for instance, seek to repeat whatever actions triggered the bliss.

In Strathearn's 2008 study published in the journal Pediatrics, when mothers saw their babies’ smiling faces, their reward signals became activated.

"These are similar brain regions that are activated when a cocaine addict gets a shot of cocaine," said Strathearn said. "So for moms, it may be like having a natural high."

How a child’s brain develops may be influenced by mom

Motherhood doesn't just influence a mom's brain — her mothering behaviors may have a lasting impact on her child's brain.

In a 2009 study published in the journal Neuropsychopharmacology, researchers looked at two groups of mothers, dividing them based on how attached they felt to their own mothers.

They found both groups responded differently to their infant's faces.

"For mothers with 'secure' attachment, we found that both happy and sad infant faces produced a reward signal in their brain," Strathearn said.

But moms with an "insecure" attachment didn't show the same brain response. When they saw their baby cry, part of the brain that is linked with pain, unfairness or disgust became activated.

"Biologically, there seems to be a pattern that is repeated from one generation to the next," Strathearn said. "Early experiences we have in childhood play an important role in the pattern of brain development."

Strathearn said that in early infancy, "the brain is being sculpted in response to its social environment, like being rocked and touched." But he noted that many factors, including genetics and the environment, influence a child's development.

Ultimately, Strathearn said he hopes future research will help experts better understand the impact that early maternal care can have on child's social, emotional and physical development.

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