Socioeconomic Status (SES) and Brain Structure over the First 2 Years of Life

• In Event: 3-169 - Socioeconomic Status, Brain, and Cognitive Development: Environmental Mechanisms and Individual Differences

Integrative Statement

This study examined the effects of SES on infant brain structure, assessed longitudinally at ages 1, 12 and 24 months, in a small sample of very low-to-middle SES infants. Our questions were: (1) Does SES affect brain volumes?, (2) Is there regional specificity to this effect?, (3) How is infant brain structure influenced by the environment?, and (4) which environmental factors are responsible for SES effects?
Method: We enrolled mothers (without significant medical, or psychiatric problems) and their healthy newborn African American female infants (n=47, born 38-42 weeks post conception and appropriate size for gestational age). Infants were scanned at 3T, without sedation, and analysis was performed on T2 and T1 weighted 1-month scans and T1 alone for older infants. Images were processed using the ANTs pipeline and segmented into cortical GM, deep GM, WM and CSF. Each subject’s brain was further parcellated into frontal, temporal, parietal, and occipital volumes based on multi-atlas segmentation. Self-reported maternal income and education were combined for an SES composite score. Two major dimensions of the child’s environment were assessed by home visits and mothers’ responses to questionnaires: Cognitive Stimulation (CogStim) used 18 items selected for maximal face validity from the HOME inventory (eg. Parent talks to child while doing household work; Child has 3 or more books of his or her own). Emotional Nurturance (EmotNurt) used 11 HOME items (Parent’s voice conveys positive feelings toward child; Parent keeps child in visual range, looks at often) and the Child Domain subscale of the Parenting Stress Index (eg, mother reports that dyadic interactions are positively reinforcing).
Results: Mixed models, with covariates age and age squared, tested effects of SES on brain volumes. Table 1 shows that SES predicted cortical GM, WM, frontal and temporal lobe volumes. Also shown are results of regressions testing CogStim and EmoNurt with the same covariates, showing CogStim, but not EmotNurt, was also predictive. CogStim was therefore tested as a mediator of SES-volume relations for cortex, white matter, frontal and temporal volumes. Although indirect pathways for WM and temporal lobe were borderline significant, in no case was there significant mediation of SES-volume effects.
Conclusions: We examined the SES-volume relation over the first two years of life and localized it to particular lobes. Frontal and temporal lobe volume showed the clearest relation to SES. Concerning the environmental factors responsible for the SES effects, it has been hypothesized that both constructs such as CogStim and EmotNurt could be responsible (Bradley & Corwyn, 2002). Only CogStim was related to brain volumes measured here, however it did not mediate SES effects.
Comment: Small sample limits study power, and hence null results are particularly ambiguous. Nevertheless, positive findings indicate early effects of SES on cortical GM and WM, as well as frontal and temporal lobe volumes. Role of cognitive stimulation, and changes over development, remain to be better understood.

Authors

• Laura M. Betancourt, he Children's Hospital of Philadelphia, Division of Neonatology
  Presenting Author

• Thomas A. Nichols, Department of Psychology, University of Pennsylvania
  Non-Presenting Author

• Martha J. Farah, Center for Neuroscience & Society, University of Pennsylvania
  Non-Presenting Author

• Brian Avants, Department of Radiology and Medical Imaging, University of Virginia
  Non-Presenting Author

• Okan Elci, Westat; The Biostatistics and Data Management Core, The Children's Hospital of Philadelphia
  Non-Presenting Author

• Hallum Hurt, The Children's Hospital of Philadelphia, Division of Neonatology
  Non-Presenting Author