It may seem too small a space to house feelings so intense and complex, but the small walnut-shaped structure at the very core of our brain -- the amygdala -- serves as a kind of jewelry box in which we nurture and store our attachment to our mother. A new study peers into the workings of the amygdala in children who were adopted from orphanages abroad, and finds that for some, mother and stranger are not so far apart.
The study, conducted by researchers at UCLA on a group of children who experienced institutional care during their infancy, suggests that the absence of a mother's care results in brains that are shaped and wired differently from the brains of babies who had a predictable primary caregiver in the critical first years of life. Even years after they are welcomed into a family, such children may respond to strangers with unnerving affection.
The study was published this week in the journal Biological Psychiatry.
In a brain scanner, those differences were readily observable: When shown photos of their moms alternating with images of similar women who were strangers, the amygdalae of children who started life in their mother's arms drew a sharp distinction between the two women. The amygdalae of children who were adopted after an infancy in institutional care did not sharply distinguish between the stranger and the woman they called mother.
The differences were more pronounced the longer the period of institutionalized care the child had experienced before his or her adoption. And they became less pronounced as children had been with their adoptive families longer.
At the same time, the researchers observed a clear link between the brain's response to pictures of mother and the child's behavior toward strangers: When the amygdala responded differently to mother's face than it did to that of a stranger, the child was more likely to be shy or standoffish around strangers; when the amygdala did not sharply distinguish between images of mother and another, unknown woman, the child was more likely to show what psychologists call "indiscriminate friendliness" toward strangers.
"This can be a very frightening behavior for parents," said Nim Tottenham, an associate professor of psychology at UCLA and the study's senior author. "The stranger anxiety or wariness that young children typically show is a sign that they understand their parents are very special people who are their source of security. That early emotional attachment serves as a bedrock for many of the developmental processes that follow."
This behavioral quirk is widely seen in children who spent their infancy in orphanages. Researchers have long suggested that such openness may be an adaptive strategy for babies to elicit the care of strangers. The new study suggests, however, that the strategy that may improve these babies' odds of having their needs met in infancy may shape their brains and their behavior under very different circumstances.
"These behaviors continue after adoption, and it has been suggested that, because of their enduring nature, they might be understood in terms of biological adaptations at the level of brain development."
The study compared 33 previously institutionalized children ages 6 through 15 with 34 children from 4 to 17 years of age. It is part of a larger study, funded with a grant from the National Institute of Mental Health, that is examining brain development in children with histories of institutional care-giving. Just over three-quarters of the study's adopted participants were born in Eastern Europe; the remainder were born in East or South Asia.