Measuring Nurture: Study Shows How “Good Mothering” Hardwires Infant Brain

By carefully watching nearly a hundred hours of video showing mother rats protecting, warming, and feeding their young pups, and then matching up what they saw to real-time electrical readings from the pups’ brains, researchers at NYU Langone Medical Center have found that the mother’s presence and social interactions — her nurturing role — directly molds the early neural activity and growth of her offsprings’ brain.

Reporting in the July 21 edition of the journal Current Biology, the NYU Langone team showed that the mother’s presence in the nest regulated and controlled electrical signaling in the infant pup’s brain.

Although scientists have known for decades that maternal-infant bonding affects neural development, the NYU Langone team’s latest findings are believed to be the first to show — as it is happening — how such natural, early maternal attachment behaviors, including nesting, nursing, and grooming of pups, impact key stages in postnatal brain development.

Researchers say the so-called slow-wave, neural signaling patterns seen during the initial phases of mammalian brain development — between age 12 and 20 days in rats — closely resembled the electrical patterns seen in humans for meditation and conscious and unconscious sleep-wake cycles, and during highly focused attention. These early stages are when permanent neural communication pathways are known to form in the infant brain, and when increasing numbers of nerve axons become sheathed, or myelinated, to speed neural signaling.

According to senior study investigator and neurobiologist Regina Sullivan, PhD, whose previous research in animals showed how maternal interactions influenced gene activity in the infant brain, the latest study offers an even more profound perspective on maternal caregiving.

“Our research shows how in mammals the mother’s sensory stimulation helps sculpt and mold the infant’s growing brain and helps define the role played by ‘nurturing’ in healthy brain development, and offers overall greater insight into what constitutes good mothering,” says Sullivan, a professor at the NYU School of Medicine and its affiliated Nathan S. Kline Institute for Psychiatric Research. “The study also helps explain how differences in the way mothers nurture their young could account, in part, for the wide variation in infant behavior among animals, including people, with similar backgrounds, or in uniform, tightly knit cultures.”

“There are so many factors that go into rearing children,” says lead study investigator Emma Sarro, PhD, a postdoctoral research fellow at NYU Langone. “Our findings will help scientists and clinicians better understand the whole-brain implications of quality interactions and bonding between mothers and infants so closely after birth, and how these biological attachment behaviors frame the brain’s hard wiring.”

For the study, a half-dozen rat mothers and their litters, of usually a dozen pups, were watched and videotaped from infancy for preset times during the day as they naturally developed. One pup from each litter was outfitted with a miniature wireless transmitter, invisibly placed under the skin and next to the brain to record its electrical patterns.

Specifically, study results showed that when rat mothers left their pups alone in the nest, infant cortical brain electrical activity, measured as local field potentials, jumped 50 percent to 100 percent, and brain wave patterns became more erratic, or desynchronous. Researchers point out that such periodic desynchronization is key to healthy brain growth and communication across different brain regions.

During nursing, infant rat pups calmed down after attaching themselves to their mother’s nipple. Brain activity also slowed and became more synchronous, with clearly identifiable electrical patterns.

Slow-wave infant brain activity increased by 30 percent, while readings of higher brain-wave frequencies decreased by 30 percent. Milk delivery led to intermittent bursts of electrical brain activity that were double or five times higher than before.

Similar spikes in rat brain activity of more than 100 percent were observed when mothers naturally groomed their infant pups.

However, these brain surges progressively declined during weaning, as infant pups gained independence from their mothers, leaving the nest and seeking food on their own as they grew past two weeks of age.

Additional experiments with a neural-signaling blocking agent, propranolol, confirmed that maternal effects were controlled in part by secretion of norepinephrine, a key neurotransmitter and hormone involved in most basic brain and body functions, including regulation of heart rate and cognition. Noradrenergic blocking in infant rats mostly dampened all previously observed effects induced by their mothers.

Sullivan says her team next plans similar experiments to look at how behavioral variations by the mother affect infant rat brain development, with the added goal of mapping any differences in brain development.

Long term, they say, they hope to develop diagnostic tools and therapies for people whose brains may have been impaired or simply underdeveloped during infancy.

Sarro says more research is also under way to investigate what other, nonadrenergic biological mechanisms might also be involved in controlling maternal sensory stimulation of the infant brain.

Nurturing may protect kids from brain changes linked to poverty

Growing up in poverty can have long-lasting, negative consequences for a child. But for poor children raised by parents who lack nurturing skills, the effects may be particularly worrisome, according to a new study at Washington University School of Medicine in St. Louis.

Among children living in poverty, the researchers identified changes in the brain that can lead to lifelong problems like depression, learning difficulties and limitations in the ability to cope with stress. The study showed that the extent of those changes was influenced strongly by whether parents were nurturing.

The good news, according to the researchers, is that a nurturing home life may offset some of the negative changes in brain anatomy among poor children. And the findings suggest that teaching nurturing skills to parents — particularly those living in poverty — may provide a lifetime benefit for their children.

The study is published online Oct. 28 and will appear in the November issue of JAMA Pediatrics.

Using magnetic resonance imaging (MRI), the researchers found that poor children with parents who were not very nurturing were likely to have less gray and white matter in the brain. Gray matter is closely linked to intelligence, while white matter often is linked to the brain’s ability to transmit signals between various cells and structures.

The MRI scans also revealed that two key brain structures were smaller in children who were living in poverty: the amygdala, a key structure in emotional health, and the hippocampus, an area of the brain that is critical to learning and memory.

“We’ve known for many years from behavioral studies that exposure to poverty is one of the most powerful predictors of poor developmental outcomes for children,” said principal investigator Joan L. Luby, MD, a Washington University child psychiatrist at St. Louis Children’s Hospital. “A growing number of neuroscience and brain-imaging studies recently have shown that poverty also has a negative effect on brain development. 

“What’s new is that our research shows the effects of poverty on the developing brain, particularly in the hippocampus, are strongly influenced by parenting and life stresses that the children experience.”

Luby, a professor of psychiatry and director of the university’s Early Emotional Development Program, is in the midst of a long-term study of childhood depression. As part of the Preschool Depression Study, she has been following 305 healthy and depressed kids since they were in preschool. As the children have grown, they also have received MRI scans that track brain development.

“We actually stumbled upon this finding,” she said. “Initially, we thought we would have to control for the effects of poverty, but as we attempted to control for it, we realized that poverty was really driving some of the outcomes of interest, and that caused us to change our focus to poverty, which was not the initial aim of this study.”

In the new study, Luby’s team looked at scans from 145 children enrolled in the depression study. Some were depressed, others healthy, and others had been diagnosed with different psychiatric disorders such as ADHD (attention-deficit hyperactivity disorder). As she studied these children, Luby said it became clear that poverty and stressful life events, which often go hand in hand, were affecting brain development.

The researchers measured poverty using what’s called an income-to-needs ratio, which takes a family’s size and annual income into account. The current federal poverty level is $23,550 for a family of four.

Although the investigators found that poverty had a powerful impact on gray matter, white matter, hippocampal and amygdala volumes, they found that the main driver of changes among poor children in the volume of the hippocampus was not lack of money but the extent to which poor parents nurture their children. The hippocampus is a key brain region of interest in studying the risk for impairments.

Luby’s team rated nurturing using observations made by the researchers — who were unaware of characteristics such as income level or whether a child had a psychiatric diagnosis — when the children came to the clinic for an appointment. And on one of the clinic visits, the researchers rated parental nurturing using a test of the child’s impatience and of a parent’s patience with that child.

While waiting to see a health professional, a child was given a gift-wrapped package, and that child’s parent or caregiver was given paperwork to fill out. The child, meanwhile, was told that s/he could not open the package until the caregiver completed the paperwork, a task that researchers estimated would take about 10 minutes.

Luby’s team found that parents living in poverty appeared more stressed and less able to nurture their children during that exercise. In cases where poor parents were rated as good nurturers, the children were less likely to exhibit the same anatomical changes in the brain as poor children with less nurturing parents.

“Parents can be less emotionally responsive for a whole host of reasons,” Luby said. “They may work two jobs or regularly find themselves trying to scrounge together money for food. Perhaps they live in an unsafe environment. They may be facing many stresses, and some don’t have the capacity to invest in supportive parenting as much as parents who don’t have to live in the midst of those adverse circumstances.”

The researchers also found that poorer children were more likely to experience stressful life events, which can influence brain development. Anything from moving to a new house to changing schools to having parents who fight regularly to the death of a loved one is considered a stressful life event.

Luby believes this study could provide policymakers with at least a partial answer to the question of what it is about poverty that can be so detrimental to a child’s long-term developmental outcome. Because it appears that a nurturing parent or caregiver may prevent some of the changes in brain anatomy that this study identified, Luby said it is vital that society invest in public health prevention programs that target parental nurturing skills. She suggested that a key next step would be to determine if there are sensitive developmental periods when interventions with parents might have the most powerful impact.

“Children who experience positive caregiver support don’t necessarily experience the developmental, cognitive and emotional problems that can affect children who don’t receive as much nurturing, and that is tremendously important,” Luby said. “This study gives us a feasible, tangible target with the suggestion that early interventions that focus on parenting may provide a tremendous payoff.”