Brain growth during the first three years of life has received considerable attention from the press and the public in recent years. But a new article in Nature, a weekly science journal, may help end the debate over whether the early years are the only important or 鈥渃ritical鈥� stage of neurological development.
By using magnetic resonance imaging, which produces images of the brain, scientists from the University of California, Los Angeles, the National Institute of Mental Health, and McGill University in Montreal have found continuing structural changes in the brain through age 15, even though the brain is already close to its adult size even before children enter school.
鈥淭he brain grows not as one piece, but in differential fits and starts for diverse regions,鈥� said Kurt W. Fischer, a professor of education at Harvard University and the director of the new Mind, Brain, and Education graduate program there. 鈥淭he Nature article shows the complexity of these growth patterns.鈥�
The researchers noted that during the early years, specifically from ages 3 to 6, most brain growth occurs in the 鈥渇rontal circuits鈥� of the brain, areas involved in the 鈥渙rganization and planning of new actions.鈥� But as children grow older, the growth moves toward the rear to the areas involved in learning language and understanding spatial relations.
This growth rate, however, drops off sharply once children reach early adolescence, the new research shows. To child-development experts, the findings are further confirmation of what earlier research and experience have long suggested.
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鈥淔or many years, it has been observed that the facility in acquiring a second language, and to speak that language without an accent, declines after the age of 10 to 12 years,鈥� said Charles A. Nelson, a professor of child development at the University of Minnesota in Minneapolis and the chairman of the Research Network on Early Experience and Brain Development, a group sponsored by the Chicago-based John D. and Catherine T. MacArthur Foundation and the James S. McDonnell Foundation of St. Louis.
Paul M. Thompson, an assistant professor of neurology at UCLA and one of the authors of the journal article, noted that another important finding is that the regions of the brain involved in learning new motor skills, such as athletics or playing a musical instrument, begin to lose tissue between ages 7 to 11.
鈥淭here is key reorganization going on in the brain at that time,鈥� he said.
Jay N. Giedd, the chief of the child psychiatry branch at NIMH, added that while children entering adolescence are at a higher risk for experimenting with drugs and alcohol, this study shows that 鈥渢his is the worst time to do it.鈥�
These findings also help to underscore that the early years are not the only 鈥渨indow of opportunity,鈥� a term from research that many advocates began using, experts say.
Advocacy Questioned
The view that what happens in a child鈥檚 life during this period sets him or her on a certain pathway鈥攁nd that certain experiences that are missed during this 鈥渨indow鈥� cannot be learned later鈥攊s one message that resulted from the sudden emphasis on the early years, which included a highly publicized conference at the White House. (鈥淐linton Announces 5 Child-Care, Early-Years Initiatives,鈥� April 23, 1997.)
Critics argued that such statements were a misinterpretation of the science and that some child-advocacy groups were picking and choosing findings from neuroscience to support their causes.
Matthew E. Melmed, the executive director of Zero to Three, a Washington-based nonprofit group focusing on services for infants and toddlers, said it is important for practitioners to look for consensus among scientists and not just base policies on the findings of one researcher.
鈥淲e were initially intrigued by what some neuroscientists were reporting, and our excitement level was maybe higher than it should have been,鈥� he said. 鈥淭hat was a sorting-out process that we had to go through.鈥�
