Experience alters brain structure and function—previous controlled studies have reported specific experience-dependent changes following training in sensory and motor tasks. Taking a step back, however, it is critical to understand how broader and less controlled influences and experiences affect the development of brain structure and function. Children from lower socioeconomic status (SES) families are known to be at a disadvantage in terms of educational and vocational achievement. Earlier studies have examined relationships between SES, characteristics of particular brain regions and cognitive skills. To date, none have looked at the influence of SES across the entire brain while accounting for genetic ancestry.
On page 773, Noble and colleagues investigated a diverse cohort of 1,099 children and adolescents from the United States, assessing whether parental education and family income, which contribute to SES, correlate with structural characteristics across the entire brain. After accounting for age and genetic ancestry, they found that parental education and family income had distinct associations with total surface area of a subset of frontal, temporal and parietal regions implicated in language and executive functions. Income uniquely accounted for the variance in surface area. Interestingly, a logarithmic relationship between income and total cortical surface area revealed that, at the lower end of the income scale, steeper increases in surface area were observed with small income increases. Surface area also partially mediated the association between income and performance in cognitive tasks.
These findings raise the possibility that interventions aimed at improving SES might positively affect cognitive function by influencing brain development, inviting a call to arms for immediate educational intervention for disadvantaged children. However, it must be noted that these findings do not demonstrate a direct causal relationship between SES and brain structure, nor do they suggest that this relationship is permanent. Additional factors can also contribute including stress, safety, nutrition and access to stimulating learning environments, and these data represent just one step forward in understanding how all of these influences affect brain development. Furthermore, similar analyses need to be performed on a more global scale, as each of these elements varies considerably across different countries. With these caveats in mind, we should recognize this study's importance in examining a subset of these broader influences on whole-brain development in a large cross-sectional cohort, and it will hopefully open the door for further studies and stimulate the development of interventional efforts to reduce SES disparities in cognitive development.
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Zarate, J. The cost of brain structure. Nat Neurosci 18, 619 (2015). https://doi.org/10.1038/nn0515-619