Babies light up their mothers' brains
By Glenna Picton
For a mother, the sight of her infant smiling or crying has a profound effect.
Baylor College of Medicine researchers found that if the mother has a secure attachment to her own parents, the sight of her own baby lights up the brain's reward centers. A report of their study appears in a recent issue of the journal Neuropsychopharmacology.
When mothers cradle their babies in their arms or play with them, the secure mothers release more of the chemical oxytocin than those whose scores on a standard test showed they are less securely attached, said Dr. Lane Strathearn, lead author of the paper and an assistant professor of pediatrics – developmental at BCM and Texas Children's Hospital. The chemical oxytocin plays an important role in childbirth, nursing and other maternal activities.
Attachment
A mother's attachment to her own infant is based on her perception of her own childhood experience, said Strathearn, who is also a research associate in BCM's Brown Human Neuroimaging Laboratory.The reward signals, measured by functional magnetic resonance imaging, are stronger in moms with a secure attachment than in those who are less securely attached or dismissing, he said.
"In a previous study, we looked at how mothers as a whole responded to seeing their own babies smiling," said Strathearn. "In this one, we looked at variations in groups of mothers."
"Understanding the neurobiological processes underlying these differences in maternal behavior may help us to identify more effective treatment and preventive strategies for neglect or abuse," said Dr. P. Read Montague, professor of neuroscience and psychiatry and behavioral sciences and director of the Brown Human Neuroimaging Lab at BCM and senior author of the report.
Mother-infant attachment
"Our previous research has shown the importance of the mother-infant attachment relationship in human development," said Strathearn. "We have observed significant differences in early maternal care-giving that we think may be linked with systems in the brain related to dopamine and oxytocin."
This study sought to find out how the brains of different kinds of mothers react to their infants.
To accomplish this, the researchers recruited first-time mothers in the third trimester of their pregnancies and monitored them for 14 months after their babies were born. Before the babies were born, the women took part in an interview that asked about childhood relationships with their parent or guardians. From those interviews, the researchers determined each woman's attachment pattern. Neither the mothers nor the researchers involved in the study knew the outcome of these interview analyses until the study was over.
Oxytocin levels
At various times in the study, the researchers compared functional magnetic imaging findings and oxytocin levels for 15 of the women found to have a secure attachment and 15 found to be insecure or dismissing. (The attachment patterns of other women in the study did not fall into these groups.)
In the 14 months after birth, the mothers and infants visited the laboratory three times. During these visits, researchers took blood measurements of oxytocin and performed functional magnetic resonance scans on the mothers to determine how their brains responded to pictures of their own and other infants. Oxytocin levels were taken before, during and after the mothers played with their infants in a typical setting.
The scans showed that seeing photos of their infants caused the brains of securely attached mothers to light up more (indicating greater activity) in the brain's reward centers than did the brains of the less securely attached mothers.
More secure, more oxytocin
Securely attached mothers also produced more oxytocin when they interacted with their babies than did the other moms.
Other researchers who took part in this study include Drs. Peter Fonagy of University College London in the United Kingdom and Janet Amico of the University of Pittsburgh School of Medicine.
Funding for this research came from the National Institute of Child Health and Human Development and the National Institutes of Health; the Kane Family Foundation; the National Institute of Neurological Disorders and Stroke; National Institute of Drug Abuse and the Menninger Foundation.
