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Developmental biology - Hippocampus

Mom's love good for child's brain

New research shows that children nurtured by their mothers early in life have a larger brain hippocampus...

School-age children whose mothers nurtured them early in life have brains with a larger key structure important to learning, memory and adaptation to stress - the hippocampus. New research by child psychiatrists and neuroscientists at Washington University School of Medicine, St. Louis, is the first to show changes in this critical region of a child's brain are linked to a mother's nurturing behavior. The work appears in Proceedings of the National Academy of Sciences Early Edition - PNAS.
"This study validates something that seems so intuitive, which is just how important nurturing parents are in creating adaptive human beings. I think the public health implications suggest we should pay more attention to parents' nurturing, and we should do what we can as a society to foster these skills because clearly nurturing has a very, very big impact on later development."

Joan L. Luby MD, Washington University School of Medicine, Department of Psychiatry, St. Louis, Missouri, USA, and first author.

The new study involved children who formerly participated in a Luby study of depression in children. That study involved children who either displayed symptoms of depression or other psychiatric disorders, compared to mentally healthy children with no known psychiatric problems. As part of that initial study, children were closely observed and videotaped interacting with a parent, almost always a mother, while waiting to open an attractive gift. How much or how little the parent was able to support and nurture the child during this stressful circumstance - designed to approximate stresses in daily parenting - was evaluated by observers who knew nothing about the child's mental health or the parent's temperament.
"Whether a parent was considered a nurturer was not based on a parent's self-assessment, but on their behavior and the extent to which they nurtured their child under challenging conditions."

Joan L. Luby MD

Observations of parents and children didn't occur in their homes. For the new study, researchers conducted brain scans on 92 of the children who either had symptoms of depression or were mentally healthy when they were under observation. The brain scans revealed that children without depression and who had been nurtured, have a hippocampus almost 10 percent larger that children whose mothers were not as nurturing.

"This study to my knowledge, is the first that actually shows anatomical change in the brain validating the very large body of early childhood development literature, and highlighting the importance of early parenting and nurturing. Having a hippocampus that's almost 10 percent larger provides concrete evidence of nurturing's powerful effect," says Luby.
Luby believes the smaller brain volumes in depressed children are expected as studies in adults have shown the same results. What surprised her was how nurturing made such a big difference in brains of mentally healthy children.

Although 95 percent of parents being evaluated in the depression study were biological mothers, researchers believe the effects of nurturing on the brain are likely to be the same for any primary caregiver - whether fathers, grandparents or adoptive parents. The fact that a larger hippocampus was found in healthy, nurtured children is striking as the hippocampus is such an important brain structure.

When the body faces stresses, our brain activates an autonomic nervous system response releasing stress hormones. These hormones increase our heart rate and ease our adaptation to the stressful event. The hippocampus is the principle brain structure involved in an autonomic response. It is also key to memory and learning. A larger hippocampal volumes might suggest improved cognitive performance as well.

Past animal studies have indicated that a nurturing mother can influence brain development, and many studies in human children have identified improvements in school performance and healthier development in children raised in a nurturing environment. But until now, there wasn't solid evidence linking a nurturing parent to changes in their child's brain anatomy.
"Studies in rats have shown that maternal nurturance, specifically in the form of licking, produces changes in genes that then produce changes in receptors which increase the size of the hippocampus. This phenomenon has been replicated in primates, but it hasn't really been clear whether the same thing happens in humans. Our study now suggests a clear link between nurturing and the size of the hippocampus."

Joan L. Luby MD

One of the most fascinating questions in psychology and neuroscience pertains to how young children gain the capacity to remember their past. Early hippocampal processes have been implicated in this ability, but a lack of viable methods has hindered assessments of their contribution in early human development. We employed a functional magnetic resonance imaging paradigm that captures memory-related hippocampal function during natural nocturnal sleep in toddlers. Our results provide direct evidence of a connection between hippocampal function and early memory ability. This experimental approach overcomes previous challenges and promises to pave the way to investigations linking changes in brain function to early development of learning mechanisms, including applications to typical and atypical development.

Nonhuman research has implicated developmental processes within the hippocampus in the emergence and early development of episodic memory, but methodological challenges have hindered assessments of this possibility in humans. Here, we delivered a previously learned song and a novel song to 2-year-old toddlers during natural nocturnal sleep and, using functional magnetic resonance imaging, found that hippocampal activation was stronger for the learned song compared with the novel song. This was true regardless of whether the song was presented intact or backwards. Toddlers who remembered where and in the presence of which toy character they heard the song exhibited stronger hippocampal activation for the song. The results establish that hippocampal activation in toddlers reflects past experiences, persists despite some alteration of the stimulus, and is associated with behavior. This research sheds light on early hippocampal and memory functioning and offers an approach to interrogate the neural substrates of early memory.

Authors: Janani Prabhakar, Elliott G. Johnson, Christine Wu Nordahl, and Simona Ghetti.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1805572115/-/DCSupplemental.

Funding for this research comes from grants awarded by the National Institute of Mental Health of the National Institutes of Health (NIH).

Washington University School of Medicine's 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked fourth in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.

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Jun 22, 2018   Fetal Timeline   Maternal Timeline   News   News Archive

The hippocampus ends just behind our eyes, and each of its horns is tipped by the amygdala in purple. Image credit: Neurobiological Effects of Childhood Abuse.

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