Inequality linked to differences in kids' brain connections

By the time they are in the upper grades of elementary school, children from families with fewer resources have different patterns of connections between their many regions and networks of the brain compared to children from more affluent homes and neighbourhoods.

The number of years of education a child's parents has, according to a new study led by two University of Michigan neuroscientists and published in Developmental Cognitive Neuroscience, stood out in the study as being more significant to brain development than other socioeconomic factors.

But as the researchers dug deeper, they found that there are other factors that can affect brain connectivity besides the number of diplomas or degrees parents have earned. Additionally, they discovered a place for parenting practices like reading to kids, discussing ideas with them, taking them to museums, or engaging in other cognitively stimulating activities.

The new study uses behavioural and brain scan data from more than 5,800 tween children from various socioeconomic backgrounds across the country. The term "functional connectomes" refers to maps of interconnectivity across hundreds of brain regions, and this study represents the most comprehensive examination of how socioeconomic factors influence children.

It's also potentially relevant to public policy. One in seven American children lives in poverty using the standard definition, and half qualify for free or reduced school lunches.

"We need to better understand how social and economic inequality shapes children's brains as they grow and develop, and our results point to a key role for parents' education levels and the kind of enrichment they provide at home," says Chandra Sripada, M.D., PhD, the lead author and a professor of psychiatry and philosophy at U-M.

"Because of our sample size and 'brain-wide' analysis approach, we feel this study's results are more reliable than previous work, which tended to look at a few dozen children and a small set of brain regions at a time."

Scans and socioeconomics

The nationwide ABCD Study research project, which enrolled more than 11,000 kids at 22 sites across the country, including hundreds who participated through the University of Michigan Department of Psychiatry and Addiction Center, allowed for the large study size. Data from more than half of them, including fMRI (functional magnetic resonance imaging) brain scans, were used to create the new study.

When the kids were lying motionless in the scanner during those scans, their brain activity was recorded. Neuroscientists can observe the volume of activity between various brain regions in this relaxed state, as well as the functional connections that form from before birth through childhood and adolescence.

To make sure that their conclusions are as reliable as possible, Sripada and his colleagues, including senior author and professor of psychiatry Mary Heitzeg, PhD, conducted three analyses of the data: across the entire brain, across all major networks within the brain, and across all individual brain connections.

The team "taught" a computer to predict a child's level of socioeconomic resources solely based on patterns of interconnections among brain regions using machine learning. They demonstrated that the patterns the computer learned generalize to new kiddos that it had never "seen." This analysis revealed that children from various socioeconomic backgrounds had very different patterns of brain connectivity.

The researchers examined a composite measure of the overall socioeconomic resources of a child's household, combining measures of parental education, household income and levels of neighbourhood resources. In addition, the researchers examined the unique contributions of each of these three socioeconomic factors.

That's where parental education rose to the fore as the most associated with variations in brain connections.

"The effects of household socioeconomic resources on functional connectivity were massively distributed throughout youths' brains," says Sripada. "We did not see the localization of effects in a discrete location or specific brain circuit. Instead, there were relatively tiny effects distributed throughout the brain, though when these individual effects are aggregated together, they constitute a strong, reliably detected signal."

He notes that this mirrors the evolving understanding of the genetics involved in diseases from schizophrenia to diabetes, where tiny effects from many genes combine to create the whole picture.

Is it parental education or parenting activities that matter?

The researchers were able to examine additional data for a subset of 3,223 kids in order to determine what elements might contribute to the explanation of why parental education is linked to variations in children's brain connectivity patterns.

They discovered that parents with higher education levels participated in more at-home enrichment activities, and the children of these parents performed better on cognitive function tests and earned higher grades in school.

"Based on these results, we see parental education as potentially an important part of the more complex pathway by which socioeconomic disparities get 'under the skin' and shape the developing brain," says Heitzeg. "As data from the long-term ABCD study continues to become available, we look forward to exploring how different factors influence physical and mental health, use of drugs and alcohol, and more."

The "crisis of reproducibility" in neuroscience, which occurs when researchers examine very small samples but their findings are not replicated in subsequent small studies, is something Sripada says he hopes the new findings will help address. He hopes that robust, trustworthy results from sizable studies will boost confidence in neuroscience and increase the likelihood that these results will be used to guide social and policy questions. (ANI)