Scientists today offered their first insights at research on a group of "super-healthy" children from six U.S. cities whose brains will serve as models of typical childhood development.
Initial results from the National Institutes of Health study suggest that healthy children perform better on cognitive tests than researchers previously thought - and this was particularly true among children from low-income families.
Yet, experts said today's conclusions - published in the Journal of the International Neuropsychological Society - are less important than what's to follow: digital images of the children's brains collected as they grow and develop.
Those images, combined with results from the cognitive and behavioral tests, will serve as a guide to childhood brain development and a benchmark against which to compare the brains of children with developmental disorders and diseases.
The researchers also hope the results will help illuminate the underlying causes of developmental problems such as attention deficit disorder and autism. They plan to publish the results in a database and to make it freely available to other scientists.
"This database will be like a library of brains that investigators can use to compare to other populations of children with disease and disorders," says Deborah P. Waber, Harvard Medical School psychologist and lead author of the paper published today.
"If we understand the processes by which the normal brain develops and the ways it can go off track," she says "it might help us to develop more focused therapies so children can get back on track."
To find a group of healthy children, the NIH researchers screened more than 35,000 youngsters for medical, neurologic and psychiatric disorders, as well as for family histories that point to potential problems or prenatal exposure to toxins. Only 450 of the children met the strict criteria.
The children's mental acuity and social skills were assessed using a variety of tests commonly used by psychologists. They also underwent magnetic resonance imaging (MRI) of their brains, a procedure deemed safe for children.
The study, which took six years to complete, tracked children from different age ranges for four years each. The results from the different groups were combined to produce a map of development from birth to early adulthood.
Experts said today's report - which did not include the MRI results - indicates that the NIH study may provide a more accurate depiction of normal brain development than earlier studies.
It was seen that the children in the new study outperformed those in previous research on a variety of tests that measured IQ, memory, reading and math ability, and development of social skills.
Dr. James C. Harris, a professor of psychiatry and pediatrics at the Johns Hopkins University School of Medicine, said the rigorous screening process probably identified a particularly healthy group of children.
"You get a more refined view," he said. "You get a more accurate portrayal of development in healthy children. With that baseline you can go to disorders like autism and say, 'What happens when brain structures don't develop normally?'"
The careful screening of participants may also help scientists better understand differences in cognitive performance that are linked to gender and family income.
For example, the results published today showed that children from families with lower incomes tended to have lower IQ scores and more difficulty with complex tasks such as reading comprehension.
Children from families with yearly incomes of less than $35,000 per year had a mean IQ of 105. In comparison, those with family incomes of $35,000 to $75,000 had mean IQs of 110, and those with family incomes of over $75,000 had IQs of 115.
Low-income children were also more likely to be excluded from the study because of medical or behavioral problems. "This should make people think more about physical and mental health conditions that interfere with children's development," Waber opines.
On a positive note, the gap between children from rich and poor families was smaller than that found by previous research, a difference Waber attributed to the NIH study's rigorous screening procedure.
By doing a better job at finding truly healthy children from low-income families, she said, the researchers produced a more accurate portrayal of their abilities and development.
The study also found less difference between boys and girls than previous research. However, it supported earlier findings that girls seem to have slight advantages at verbal learning and boys seem to be a little better at analyzing and manipulating shapes and patterns.
The findings also support a period of rapid brain development between ages 6 and 11. "The basic building blocks seem to be in place by the time someone reaches 11 or 12," Waber said.
She said the MRI data on the children - some of which are expected to be released this summer - will help scientists see how the structures and connections in the brain change during that rapid period of development.
"It's not just that the brain gets bigger," she said. "Certain structures in the brain become smaller or change shape. To actually see any changes in the connections in the brain and relate it to function is going to be very interesting," Waber added.