Childhood Environment and Adult Brain Structure: Experimental Evidence

• In Event: The Environment’s Role in Cognitive Development across Contexts and Developmental Stages

Abstract

Introduction: Despite a large animal literature showing a causal role for environmental stimulation on brain structure, nothing is known about the kinds of stimulation that matter especially for humans: linguistic and conceptual. Observational studies of humans cannot demonstrate a causal role of such stimulation; they are susceptible to alternative accounts based on genetic inheritance. Perhaps both the level of environmental enrichment provided by parents and their neurocognitive abilities are determined by genes, and they pass these genes on to their children, accounting for the child environment-trait association without environmental causality (eg, Murray, 2020). Here we test the potential causal role of cognitive and linguistic stimulation by leveraging the well-known Abecedarian early intervention project (Ramey et al., 2000). Hypothesis: The experience of an enriched environment from birth to 5 yo would have lasting effects on brain structure in low-income children. Based on animal studies (Rosenzweig, Bennet & Diamond, 1972), we predicted larger regional volumes in areas associated with the processes targeted by the intervention, which was based on the Vygotskian idea that language supports children’s thinking and self-control (ROIs: left inferior frontal gyrus and left superior temporal gyrus (language), right inferior frontal gyrus and bilateral ACC (cognitive control) and bilateral hippocampus (learning). Study population began as healthy but high-risk infants, based on their families’ extreme poverty and multiple associated factors such as father absence and low parental education or IQ. Participants were evaluated throughout the period of the intervention and after. Cognitive benefits were substantial through the school years then diminished in adulthood, though some remained significant at age 21 (Campbell et al., 2001). Enduring effects were found in real-world measures such as rates of full-time employment (Ramey, Sparling & Ramey, 2012). Methods: At age approximately 40, participants were invited to undergo MRI. 47 participants agreed and were successfully scanned (29 from the intervention group, 18 from the comparison group). Groups were well-matched (see table). ANOVA was carried out on the summed ROIs with covariates age, sex and a later intervention, and interactions. Individual ROIs were also examined. Results: Summed ROIs for the Comparison group in cc, mean (SE) were 25.72 (0.6) and 25.59 (0.84) for males and females respectively. Corresponding values for the Intervention group were 29.7 (0.52) and 26.49 (0.63). The summed ROIs showed a highly significant effect of the intervention by ANOVA as described earlier, by standard and permutation tests (p<0.001 for both). Also notable was the sex-by-group interaction. Figure 1 shows individual region effects, with 95% confidence intervals. Males were more affected, a finding that was not expected but is also not unprecedented (Campbell et al, 2014; Garcia et al., 2018). In conclusion, early intensive cognitive and linguistic stimulation shapes human brain structure. The causal mechanisms are unknown and may constitute a chain of causal processes. Nevertheless, the results support the influence of the early environment on the brain structure of individuals growing up in poverty, a finding with relevance to the basic science of brain development, as well as theories of social stratification and social policy.

Authors

• Martha J Farah, University of Pennsylvania
  Presenting Author

• Saul Sternberg, University of Pennsylvania
  Non-Presenting Author

• Tanner Nichols, University of Pennsylvania
  Non-Presenting Author

• Jeffrey Duda, University of Pennsylvania
  Non-Presenting Author

• Terry Lohrenz, Virginia Tech University
  Non-Presenting Author

• Yi Luo, Virginia Tech University
  Non-Presenting Author

• Libbie Sonnier, Louisiana Policy Institute for Children
  Non-Presenting Author

• Sharon L. Ramey, Virginia Tech
  Non-Presenting Author

• Read Montague, Virginia Tech University
  Non-Presenting Author

• Craig T Ramey, Virginia Polytechnic Institute and State University
  Non-Presenting Author