Study Peeks at How Normal Brains Grow

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Study Peeks at How Normal Brains Grow

Friday, May 18, 2007

Can you get smarter than a fifth-grader? Of course, but new research

suggests some of the brain's basic building blocks for learning are

nearing adult levels by age 11 or 12.

It is the first finding from a study of how children's brains grow.

The most interesting results are yet to come.

About 500 super-healthy newborns to teenagers, recruited from super-

healthy families, are having periodic MRI scans of their brains as

they grow up. They also get a battery of age-appropriate tests of

such abilities as IQ, language skills and memory.

The project, funded by the National Institutes of Health, is tricky

work.

Move during an MRI, and the image blurs. Because scientists cannot

sedate healthy children, they are having to get crafty to keep their

subjects still. Tired toddlers are put in the scanners at naptime;

mom squeezes in for a cuddle and earplugs help block the machines'

noisy banging. Six-year-olds wear earphones and watch favorite videos

beamed into the scanner.

The MRI images measure how different parts of the brain grow and

reorganize throughout childhood.

Overlap them with the children's shifting behavioral and intellectual

abilities at each age, and scientists expect to produce a long-sought

map of normal brain development in children representative of the

diverse U.S. population.

On Friday, scientists were publishing a sneak peek at some surprising

early results.

Performance on a variety of cognitive tasks _ working memory,

vocabulary, spatial recognition, reasoning, calculation _ rapidly

improves between age 6 and 10, but then levels off.

" We don't honestly know why, " said Dr. Deborah Waber of Children's

Hospital Boston, who led the analysis published in the Journal of the

International Neuropsychological Society.

This is a snapshot of 6- to 18-year-olds' abilities during their

first study visit. Results may change after researchers observe each

child's progress with age and compare their MRI scans, she said.

The adolescent brain is still growing. Indeed, the region responsible

for things such as impulse control and moral judgment is the last to

mature, sometime in the early 20s, said Dr. Jordan Grafman of the

NIH's National Institute of Neurological Disorders and Stroke.

The study did not evaluate those kinds of skills. " It's an incomplete

picture, " he said.

But the age finding does make sense, suggesting a foundation

necessary for higher learning is in place by puberty, said Dr.

Gilmore of the University of North Carolina School of Medicine. The

brain-development specialist was not involved with the project.

Scientists already knew that before age 12, the brain is racing to

wire itself, making more connections between nerve cells that in turn

enlarge vital regions. This is a time of rapid learning, the reason

it is easier to learn a foreign language as a young child than as a

teenager or adult, Gilmore said.

After puberty, the process slows and the brain " prunes " itself,

focusing less on installing new wiring than on programming and

refining what is already there.

" Obviously, learning continues to happen, " Gilmore said. But the new

study says that " by 10 or 12, kids have the basic building blocks

they need to learn. "

The study also found that girls start with a slightly better verbal

ability but boys catch up by adolescence; they have an equal aptitude

for math. While children from low-income families scored slightly

lower on IQ tests, earlier suggestions of a bigger gap are due to

poorer health among poor families.

Once those key MRI scans are added to the children's ability tests,

scientists will have a better idea of the range of normal childhood

development. Then they can use the data to help figure out what goes

wrong in brain diseases such as autism.