In new research published in the Journal of Cognitive Neuroscience, low socioeconomic status infants were randomized to either five years of cognitively and linguistically stimulating center-based care or a comparison condition; the intervention resulted in large and statistically significant changes in brain structure measured in midlife, particularly for male individuals.
A teacher guides a student through a task in this historical photo of the Abecedarian Project. Image credit: Virginia Tech.
How does early life experience shape the human brain? The question is surprisingly difficult to answer, as it concerns the causes, rather than merely the correlates, of individual differences in human development.
Studies of such differences are normally observational and thus silent on the subject of causality.
Animal studies, in contrast, have demonstrated causal influence of environmental stimulation on brain structure using random assignment to physical environments with low or high complexity.
However, they cannot tell us about the features of the environment that matter most for human development: linguistic and cognitive stimulation.
The role of the environment in shaping brain development is a central issue for neuroscience, and a significant open question concerns the impact of uniquely human features of the environment, namely, linguistic and cognitive stimulation.
Whereas a large animal literature shows that more complex cage environments lead to microscopic and macroscopic brain changes, including larger cortex, such manipulations provide an incomplete model for the environmental differences that may matter most in human development.
These include differences in complex forms of cognitive and linguistic experience.
“Our research shows a relationship between brain structure and five years of high-quality, educational and social experiences,” said Professor Craig Ramey, a researcher in the Fralin Biomedical Research Institute at the Virginia Polytechnic Institute and State University.
“We have demonstrated that in vulnerable children who received stimulating and emotionally supportive learning experiences, statistically significant changes in brain structure appear in middle age.”
“The results support the idea that early environment influences the brain structure of individuals growing up with multi-risk socioeconomic challenges,” added Dr. Martha Farah, director of the Center for Neuroscience and Society at the University of Pennsylvania.
“This has exciting implications for the basic science of brain development, as well as for theories of social stratification and social policy.”
The study involved participants of the Abecedarian Project, which was established in North Carolina in the early 1970s.
The project initially enrolled 112 predominantly African American infants from homes of very low SES (low income and maternal education) with multiple associated risk factors such as paternal absence, welfare receipt, and low parental IQ, but free of neurodevelopmental disorder.
One of the 112 infants later received a diagnosis of a congenital condition that was disqualifying based on the exclusionary criteria, resulting in 111 infants participating in the study.
Both the comparison and treatment groups received extra health care, nutrition, and family support services.
However, beginning at six weeks of age, the treatment group also received five years of high quality educational support, five days a week, 50 weeks a year.
During follow-up examinations, structural MRI scans were obtained from 47 of the Abecedarian sample, 29 from the early intervention group and 18 from the comparison group.
When scanned, the participants were in their late 30s to early 40s, offering the researchers a unique look at how childhood factors affect the adult brain.
Analyzing the scans, the authors looked at brain size as a whole, including the cortex, the brain’s outermost layer, as well as five regions selected for their expected connection to the intervention’s stimulation of children’s language and cognitive development.
Those included the left inferior frontal gyrus and left superior temporal gyrus, which may be relevant to language, and the right inferior frontal gyrus and bilateral anterior cingulate cortex, relevant to cognitive control.
A fifth, the bilateral hippocampus, was added because its volume is frequently associated with early life adversity and socioeconomic status.
The scientists determined that those in the early education treatment group had increased size of the whole brain, including the cortex. Several specific cortical regions also appeared larger.
They also noted the group intervention treatment results for the brain were substantially greater for males than for females.
The reasons for this are not known, and were surprising, since both the boys and girls showed generally comparable positive behavioral and educational effects from their early enriched education.
“When we launched this project in the 1970s, the field knew more about how to assess behavior than it knew about how to assess brain structure,” Professor Ramey said.
“Because of advances in neuroimaging technology and through strong interdisciplinary collaborations, we were able to measure structural features of the brain.”
“The prefrontal cortex and areas associated with language were definitely affected; and to our knowledge, this is the first experimental evidence on a link between known early educational experiences and long-term changes in humans.”
“We believe that these findings warrant careful consideration and lend further support to the value of ensuring positive learning and social-emotional support for all children — particularly to improve outcomes for children who are vulnerable to inadequate stimulation and care in the early years of life.”
Martha J. Farah et al. 2021. Randomized Manipulation of Early Cognitive Experience Impacts Adult Brain Structure. Journal of Cognitive Neuroscience 33 (6): 1197-1209; doi: 10.1162/jocn_a_01709