In the past decade, many studies have suggested that adverse experiences early in life, including physical and sexual abuse, can leave lasting marks on the brain, subtly altering both the structure and function of key areas. But as the neuroscience community has moved away from taking a nature versus nurture stance when it comes to understanding brain development—now placing more emphasis on how the two influence each other—scientists are learning that perhaps all of our early life experiences, good and bad, help shape our future brains. Two new studies presented at this year’s Society for Neuroscience meeting support this notion, suggesting that both socioeconomic status (SES) and cognitive enrichment early in life are linked to measureable anatomical changes in the brain.
Decades of psychological and epidemiological research have concluded that SES, a standardized measure of a family’s social and economic position in relation to others, can have profound impact on later life outcomes. SES has been linked to remarkable differences in both cognitive and emotional development; lower SES is correlated with lesser abilities in working memory, language, memory, and inhibitory control. But while this correlation can be described easily in many ways at the behavioral level, it has been more difficult to pin down in a biological context.
“We know that socioeconomic disadvantage in childhood can affect the whole environment, which can affect cognitive and language development,” says Suzanne Houston, a graduate student at the University of Southern California. “Children from lower socioeconomic backgrounds tend to have increased exposure to stressors, which also may impact brain development. Key studies, however, have not really shown the degree to which SES is related to changes in brain structure so far.”
To better understand how SES might be shaping these observed cognitive effects, Houston, in collaboration with Kimberly Noble, a developmental cognitive neuroscientist at Columbia University, scanned the brains of 60 typically developing children of varying SES backgrounds, using functional magnetic resonance imaging (fMRI). They used those scans to examine the relationships between SES and regional cortical volume in areas like the hippocampus, an area of the brain implicated in memory and learning, and the amygdala, an area linked to emotional processing. When breaking down SES into specific factors, they found that higher parental education levels predicted larger amygdala volumes. In contrast, higher income-to-needs ratios were linked to larger hippocampal volumes in these children. The results were presented at Neuroscience 2012 as well as published in the July 2012 issue of Developmental Science.
“The findings are consistent that variations in childhood SES lead to variations in childhood experiences,” says Houston. “So it supports the idea that SES may affect brain development, perhaps with differences in the home language environment and exposure to stress.”
Cognitive enrichment and development
There is more to a home environment, however, than just SES. Brian Avants, a researcher from the University of Pennsylvania, and Martha Farah, director of the University of Pennsylvania’s Center for Neuroscience and Society and a member of the Dana Alliance for Brain Initiatives, wondered what factors in a “normal” home environment might influence brain development.
“Oddly enough, in many ways we know more about abnormal brain development than normal development,” says Farah. “That’s partly because children who are injured or ill need our help and so we focus our attention here. Also because, in the area of environmental influences on brain development, pathologies often involve extremes of environmental influence that are easier to identify and see the effects of, such as child abuse and neglect.”
Avants, Farah, and colleagues gathered data from a group of children that had been followed for more than 20 years. Research teams had visited the homes of these children at both four and eight years of age to conduct detailed observations of the home environment. More than 10 years later, those same children had their brains scanned in a high-resolution fMRI. They group then compared cortical thickness of several brain areas, a measure that has been linked to cognitive abilities, to different variables observed in the home environment. They found having ample cognitive stimulation at age 4 predicted cortical thickness in the frontal and temporal cortexes in the late teen years
“When we talk about cognitive stimulation, we’re asking, ‘Does the child have access to at least 10 books? Does the child have toys that teach letters and numbers? Did the parents take the child to museums and zoos? ’ and so forth,” says Farah. “The findings are consistent with the idea that experience has more long-term impact earlier in life. The results do not imply that improved cognitive stimulation and support for learning would be wasted at 8, or 18, or 80 for that matter. But the results are consistent with the idea that early experience matters relatively more than later.”
What does it all mean?
Farah is quick to point out that her study is the first to look at “normal” home experience and brain development and there is still quite a bit of work to do. Yet, she says, the findings correspond with work that has been done with children raised in abusive and neglectful environments. “It’s clear that the great strength, and the great vulnerability, of the brain is its responsiveness to the environment,” she says.
So what might parents take away from these studies? Is there reason to panic about SES or the number of books found in the home during the pre-school years? Regina Sullivan, a neuroscientist at the New York University School of Medicine who studies the effects of abuse on attachment and the brain, says that parents shouldn’t worry too much about there being only one “right” way to successfully foster good development in their kids.
“Humans are successful because of their ability to adapt. Trauma sets up the brain so it can’t adapt as easily and that can lead to pathology. So obviously that should be avoided at all costs,” she says. “But many different cultures produce great, successful children. Lots of parenting styles and techniques work, regardless of background. And I’d say the keys to that success are consistency, predictability, and respect.”