The amount of mentally stimulating content in a child's home — such as the number of books that are around — may predict the structure of the child's brain later in life, a new study finds.
The results show that people who lived in enriched environments during childhood had thinner cortexes later in life. The cortex is the brain's outer layer, and studies have linked thinner cortexes with higher intelligence test scores.
The findings underscore the importance of early life experiences in brain development, the researchers said.
"The time we spend with our parents before we are in school is going to affect us probably for the rest of our lives," said study researcher Brian Avants, an assistant professor of radiology at the University of Pennsylvania.
Avants and colleagues analyzed information from 64 people who were followed for more than 20 years. When the participants were kids, the researchers evaluated their homes for things that would provide mental stimulation, such as children's books and toys for learning.
Children who lived in more stimulating environments at age 4 had thinner cortexes when they were young adults, between ages 18 and 20, Avants said.
The cortex changes in thickness throughout life, Avants said. Younger children have thicker cortices, but as we age, the cortex goes through a thinning process that trims away non-essential brain cells, and allows cells to become more specialized, Avants said.
"It really needs to be trimmed down and trained to respond to the environment that we grow up in," Avants said. "The more stimulated some parts of the brain are, the thinner they become. They've been used more, and become more specialized for certain tasks," he said.
In fact, people with thinner cortices, as seen on magnetic resonance imaging, tend to have higher IQ's, Avants said.
The study's finding held even after the researchers accounted for the parents' IQs.
Interestingly, the children's home environment at age 8 was not associated with the thickness of their cortexes in young adulthood. This could be because before age 8, the brain is particularly sensitive to its environment, the researchers said. However, it's also possible that this is because as children grow, they spend less time at home.
"At age 4, the home environment is much more of a dominant player in a child's life," Avants said. At age 8, children are likely spending a lot of time at school, he said.
The study will be presented this week at the annual meeting of the Society for Neuroscience in New Orleans.
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