EUGENE, Ore. — (Feb. 19, 2013) — University of Oregon researchers say a biological mechanism already considered a barometer for emotional regulation can be tapped in infants as early as five months old to predict behavioral responses to stressful situations. A key factor, they found, is whether the child is nurtured in a secure or disorganized setting.
The mechanism is respiratory sinus arrhythmia (RSA), which is a change of heart rate tied to breathing and regulated by the vagus nerve that stretches from the brain to the stomach, branching widely and also responsible for speech, swallowing and digestive processing.
In the new research, co-author Jeffrey Measelle, professor of psychology, says it is RSA's connection to the parasympathetic nervous system that's important because it serves as an emotional braking system following exposure to environmental stress.
►The study, as covered on NPR's All Things Considered
For the study, published in the journal Psychological Science, Measelle's team examined data from a longitudinal project that has followed women at risk for parenting problems and their children. Lead author Elisabeth Conradt, a UO doctoral student during the project but now with the Brown Center for the Study of Children at Risk in Providence, R.I., examined baseline RSA under calm conditions in 73 infants at five months of age and their behaviors a year later when their attachments to their mothers were put to a challenge.
They discovered that children with high baseline RSA at age five months were more likely to exhibit problem behavior if their childrearing had fostered disorganization. However, children with high RSA whose childrearing fostered security were the least susceptible to problem behaviors.
►Measelle on the aim of the study, 38 seconds
►Measelle on the findings, 34 seconds
"I think this study begins to answer the question of why some children reared in poverty are more likely to have negative outcomes while others do OK," Conradt said. "It may be that some infants are biologically predisposed to reap the benefits of a supportive caregiving environment, while others are unfortunately more affected by a negative caregiving environment."
Baseline RSA was measured as the babies sat on their mothers' laps and watched a calm portion of a Baby Einstein video. At 17 months, the infants were closely observed as their mothers left the room and later returned as part of a series of strange-situation procedures. How infants reacted to the separations and reunions were analyzed for clues related to their attachments to their mothers.
Two thirds of the infants had experienced sensitive caregiving, while a third had been raised in less tranquil circumstances, Measelle said. "In terms of their biological susceptibility, we were interested in a feature of the central nervous system that helps to manage our cardiovascular and respiratory responses to stress, in particular, how we recover from stressful experiences."
For infants with low baseline RSA, the researchers found, living in poverty may serve as a predictor of coming problem behavior, in general.
Most of the babies exhibited higher-than-usual problem behaviors at 17 months regardless of the type of caregiving infants experienced, Measelle said. But, he added: "Those babies who were the most susceptible biologically — those with high baseline RSA — and who had experienced aversive early caregiving faired worse than the less susceptible babies, but the biologically susceptible babies who experienced optimal early caregiving seemed to rise above it all."
The results suggest, he said, that children with biological susceptibility appear to be able to bloom like orchid flowers when raised under optimal parenting or wilt when under pressure if reared in a chaotic environment.
"I was surprised that being raised in an environment that fostered security versus disorganization was not a universally good or bad thing, that it actually depended on the physiological make-up of the infant," Conradt said. "I think this study speaks to the importance of allocating more resources to support caregivers who are parenting infants and young children in poverty. We we are seeing the effects of being raised in a difficult home environment already in toddlerhood, and particularly for some children with a specific biological make-up."
Jennifer C. Ablow of the UO's Department of Psychology also was a co-author on the study. Ablow and Measelle are co-directors of the UO's Developmental Sociobiology Lab.
"These results suggest that the autonomic nervous system and caregiving interact in complicated ways to produce different patterns of outcomes," said Kimberly Andrews Espy, UO vice president for research and innovation and dean of the graduate school. "UO researchers are using a variety of methods to elucidate how biology and the environment are inextricably linked in support of healthy development."
The National Institute of Mental Health (grant R03MH068), National Science Foundation (0643393), University of Oregon Associate Dean of Natural Sciences Discretionary Funds Award, and a fellowship to Ablow from the Oregon Community Credit Union supported the research.
About the University of Oregon
The University of Oregon is among the 108 institutions chosen from 4,633 U.S. universities for top-tier designation of "Very High Research Activity" in the 2010 Carnegie Classification of Institutions of Higher Education. The UO also is one of two Pacific Northwest members of the Association of American Universities.
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