Motherhood and the Brain: The Science Behind Kissing, Cuddling, and Making It Better

As unique and diverse as all human beings across the globe may be, they all came to the world in the exact same way: a gradual progression from zygote to fetus to infant. And all of us grew in the womb of a female host — our mothers. The first and most primal of relationships is not only experienced by every human being, but has the capacity to change every human being, socially, psychologically, and, perhaps most surprisingly, on a cerebral level.

These changes begin immediately in the mother’s brain following birth. A 2010 study concluded that the size of mothers’ brains increased shortly after childbirth. The more excitement and joy a mother expresses correlates with how much her brain grows throughout the first few months of motherhood. Increases in gray matter have been documented in the hypothalamus, amygdala, parietal lobe, and prefrontal cortex, regions responsible for emotion, reasoning, and judgment, the senses, and reward behavior. Researchers measured the enthusiasm of the mother based on the choice of words they used when interviewed. Those who used words like “special,” “beautiful,” “ideal,” and “perfect,” were more likely to increase the size of their mid-brain following childbirth.

So what brings about these changes? Pilyoung Kim, director of the Family and Child Neuroscience Laboratory, proposes that hormonal changes affecting the brain — caused by increases of levels of estrogen, oxytocin, and prolactin — happen immediately after birth. The enthusiasm of these new moms also stems from the brain’s pleasure-reward systems (particularly the substantia nigra). A sort of positive feedback loop seems to be operating: a baby’s smile can release dopamine in a mom’s pleasure-reward centers, further reinforcing maternal behavior, and quite possibly increasing maternal brain growth. Perhaps after all there’s some truth to the idiom that mothers know best.

The rewards of this interaction go beyond the mother and her infant. According to neuroscientist Stuart Basten from the University of Oxford: “If parenthood is a pleasurable — or at least tolerable — experience, the chances of deciding to produce a second or third child are surely greater. It also underwrites the chances of survival of the child.” The pleasure of being a new mother indirectly influences the perpetuation of the human species as a whole.

In addition to growth of gray matter, there are other measurable changes in the brain activity of new moms. For instance, one study demonstrates that mothers who watched silent videos of their own child produced more brain activation than those who watched videos of other babies. Brains also showed increased activity in mothers when their infant was crying as opposed to smiling. Scans of their brains suggest that particular circuits in the brain are activated when a mother distinguishes the smiles and cries of her own baby from those of other infants. These regions are the amygdala and the insula — areas associated with emotional responses and theory of mind functions.

Because of these changes in brain activity and size, a new mother develops novel abilities to protect her baby from harm. Biology professor Adam Franssen who conducted his studies with rodents, recognized that not only are mothers able to maintain their calm in stressful circumstances that would leave the rest of the room in a panic, but are also more aggressive at defending their offspring. If there is an intruder, moms will fight against it more ferociously than nonmothers. Part of detecting these threats seems to be emotional intelligence, the ability to recognize hostility, disgust, fear, or the types of emotions that would pose some sort of danger to their offspring.

Another important skill that mothers develop is a heightened sense of smell. Not only can mother rats sense the odor of infant rats in general, they can specifically distinguish their own infant’s scent. This is the result of higher concentrations of cortisol, a corticosteroid hormone that increases blood pressure and blood sugar, and reduces immune responses, according to Basten.

Additionally, mother rodents have an advantage when it comes to memory tasks. Rats with mouths to feed were much better at remembering locations of food and water, compared to those in the study who did not have offspring. These newfound capabilities have been attributed to the numerous changes that occur in a mother’s brain, from larger neurons, increased numbers of dendrites and hormone receptors, to simply more neurons firing and communicating.

The fact that a woman becomes a mother is enough to foment permanent changes in her brain. For her baby, on the other hand, changes in their newly developing brains occur largely because of actions the mother chooses to take or avoid. This begins in the very first hours of life. Skin-to-skin contact (also known as kangaroo cuddling) has numerous benefits as soon as the baby is born. Primarily, it’s a means of physical interaction and helps to regulate the baby’s temperature.

It also provides sensory stimuli, promoting an early breastfeeding response with access to colostrum, which improves both short and long-term breastfeeding, and furthermore facilitates emotional bonding. According to science writer Katherine Harmon, skin-to-skin contact helps calm babies. When held, they cry less and it helps them sleep better. There have even been some studies showing that such contact helps to facilitate their brain development — probably because they are calmer and sleep better, allowing the opportunity for more connections to grow in the brain. The infant isn’t the only one who benefits either. Kangaroo cuddling can also release oxytocin in the mother’s brain.

A factor even more critical to an infant’s developing brain than skin-to-skin contact is the question of how long they were breastfed following their birth. One study conducted at Brown University discovered that by age two, babies who had been breastfed exclusively for at least the first three months of their lives had enhanced development in key parts of the brain compared to children who were fed only using formula, or who had been weaned on a combination of formula and breast milk.

Those who had been breastfed for more than a year had even more brain growth than the first control group. The researchers confirmed their findings by performing cognitive tests on older children. They found increased language performance, visual reception, and motor control performance in the groups of children who had been breastfed. Thus, to give your child a cognitive boost from the outset, choosing breast milk over formula can engender lasting benefits.

Everyone knows that babies are really good at one thing in particular: crying. This is something that can frustrate sleep-deprived mothers and parents of newborns everywhere, to no end. Simply carrying a baby around when they wake up in the middle of the night screaming seems to be one of the most effective methods of calming them down. It’s a phenomenon that can now be explained by understanding the response of the infant’s brain. The infant’s calming response to carrying is derived from a coordinated set of regulations within the central, motor, and peripheral nervous system.

In fact, the response has been with our ancestors since well before the Stone Age. It’s an evolutionarily preserved aspect of interactions between a mother and her infant. This quieting response is determined by cross-talk between both your parasympathetic nervous system and a region of the brain called the cerebellum. It’s only through understanding the instinct and bodily changes underlying the infant carrying response that we are more able to remain calm in the face of a wailing baby, thereby allowing us to respond effectively to the infant’s needs.

By nurturing your infant and expressing empathy at every turn, you impact his or her life, long into their childhood. A study conducted at Washington University in St. Louis found that school-age children whose mothers nurtured them early in life have brains with a larger hippocampus, which is a key structure crucial to learning and memory as well as response to stress. In their efforts, researchers followed 92 students from preschool, and found that those children without depression who had been nurtured had a hippocampus almost 10 percent larger than children whose mothers had not been as nurturing. So the next time little Jimmy scrapes his knee, kiss his boo-boo and make it better. It might just give him a cognitive advantage.

Not every woman has a child, but every child has a mother — it’s a fundamental fact of the human race. Indeed, humanity would cease to exist without mothers. It’s no wonder that this intense and instinctual relationship alters the brains of both mother and child. From the increase in gray matter and distinct brain activity that provides mom with the skills to successfully rear her newborn, to the larger, healthier, happier brains of infants as a result of mom’s choice to breastfeed, to hold, to kangaroo cuddle, and to nurture — the rewards of motherhood pay cognitive and emotional dividends to both the future generation and the present one.


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