Neural correlates of socioeconomic status in the developing human brain

Abstract

Socioeconomic disparities in childhood are associated with remarkable differences in cognitive and socio-emotional development during a time when dramatic changes are occurring in the brain. Yet, the neurobiological pathways through which socioeconomic status (SES) shapes development remain poorly understood. Behavioral evidence suggests that language, memory, social-emotional processing, and cognitive control exhibit relatively large differences across SES. Here we investigated whether volumetric differences could be observed across SES in several neural regions that support these skills. In a sample of 60 socioeconomically diverse children, highly significant SES differences in regional brain volume were observed in the hippocampus and the amygdala. In addition, SES × age interactions were observed in the left superior temporal gyrus and left inferior frontal gyrus, suggesting increasing SES differences with age in these regions. These results were not explained by differences in gender, race or IQ. Likely mechanisms include differences in the home linguistic environment and exposure to stress, which may serve as targets for intervention at a time of high neural plasticity.

Figure 1

Hypothesized mechanisms by which SES operates to influence cognitive development. See text for details.

Figure 2

Family SES predicts child hippocampus and amygdala volumes. (A) Hippocampus ROI defined in orange. (B) Amygdala ROI defined in yellow. (C) Family income-to-needs ratio is positively correlated with child hippocampal volume, adjusted for child age, gender, and total cortical volume (Beta = 0.22; p < .032). (D) Number of years of parent education is negatively correlated with child amygdala volume, adjusted for child age, gender and total cortical volume (Beta = −0.29; p < .002). In all plots, regional volume is portrayed as the standardized residual, in standard deviations, after adjusting for covariates.

Figure 3

SES × Age interactions in left superior temporal gyrus and left inferior frontal gyrus. A priori ROIs defined in FreeSurfer were chosen that related to language processing. Among the 44 children whose parent education ranged from 11 to 17.5 years, SES × child age interactions were observed in (A) left inferior frontal gyrus (IFG; dark blue) and left superior temporal gyrus (STG; light blue). This is portrayed graphically in (B) left IFG (Beta = 2.769; p < .014), and (C) left STG (Beta = 2.516; p < .012), suggesting that SES differences in regional brain volume are not uniform at different ages. In all plots, regional volume is portrayed as the standardized residual, in standard deviations, after adjusting for total cortical volume. All analyses were performed using continuous variables for child age, parent education, and ROI volume, but are displayed with parental education represented in terciles, with 11–13.5 years of parental education in green; 13.5–15 years of parental education in orange; and 15–17.5 years of parental education in blue.