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'Baby brain' is a myth: A new mother's brain grows bigger

Dr. Wendy Lee Walsh

By Wendy Lee Walsh, Ph.D.

The other day I had a mother’s version of a “senior moment.” Let’s call it a mama misstep, otherwise known as “baby brain.” While frantically doing a pick-and-put home-tidying job before guests arrived, I accidently threw my laundry in the trash. Only hours later, when I was scraping the dinner plates did I notice the food waste slide into the kitchen bin and onto one of my blouses. URGH! I’ve always been convinced that when women give birth, we actually donate brain cells to our fetuses.

Now, new research shows that I was wrong. Dead wrong. Motherhood, according to brain researchers, actually makes the brain grow. Published this month in Behavioral Neuroscience, exploratory research shows that certain areas of a mother’s brain bulk up, especially in the brains of mothers who spoke most positively about their babies. The thinking is this: hormonal changes in the brain, particularly the pleasant assaults of oxytocin and prolactin, the “bonding” hormones, may cause the brain to restructure itself in response to the stimulation of a baby.

The study, done by the National Institute of Mental Health and led by neuroscientist, Pilyoung Kim Ph.D., Health, performed brain MRI’s on mothers who had just given birth, and then again a few months later. When they compared the sets of images they found that the volume of their grey matter increased in various parts of the brain – sizable increases rarely seen in adults. According to the researchers, grey matter doesn’t usually grow that fast without significant learning. The brain areas most impacted included the hypothalamus an area that supports maternal motivation; the substantia nigra and amygdale, the region responsible for reward and emotion processing; the parietal lobe that governs sensory integration, and even the prefrontal cortex, the mother of reasoning and judgment.

Most interesting is the fact that the enthusiastic mothers, those who gushed over their babies, referring to them as special and perfect, showed the greatest increases in brain growth. This supports something that attachment specialists like myself have always known: positive interactions, secure attachments, and social sensitivity can increase certain kinds of intelligence. It is through our relationships that we grow and the special tactile relationship between a new mother and her infant seems to have particular advantages.

Now the researcher’s goal is to answer the old chicken-verses-egg question. Did these neurological shifts change behavior or did mothering behaviors change the brain? For instance, all the mothers in the study were breastfeeding and scientists wonder if breastfeeding might be a possible factor in a mother’s brain growth. Also, none of the mothers in the study suffered any postpartum depression and this might be linked to the structural changes in the brain.

Next up for this study group: A similar study of adoptive mothers to help separate out hormone changes from changes that might be solely attributed to the stimulation of baby. Bigger brains can be linked to many things. In the end the question remains: Does the brain change behavior or does behavior change the brain.

And perhaps, the bigger question for me. Did my trash can look like a laundry basket, or was I just dying for a shopping trip?