Generation Gap in How Brain Works Is Found

Shifting the image of youth, scientists have discovered that children appear to use their brains to handle words far differently than do adults, suggesting a generation gap that extends to the most fundamental functions of the brain.

The new research, published today in the journal Science, highlights how dramatically children differ mentally from grown-ups, not only because they still have so much to learn but because their brains physically are in flux.

“It has implications for developmental disorders and problems in reading,” said Cornell University expert B.J. Casey, who helped pioneer brain imaging in children. “The patterns of neural activity seem to be much more diffuse in children. If they are not as efficient [as adults] in using their brains, they are going to be more susceptible to interference.”

Every parent knows all too well that children have their own way of thinking. A child’s brain, however, is much more tumultuous and much more dynamic than anyone thought, with neural growth spurts that coincide with important leaps in early learning ability, recent studies have shown.

Young people lose some cognitive abilities as their brains mature and gain others in the neural tug and pull of age and experience.

From cradle to grave, the human brain adapts, shifts and transforms itself in ways scientists only now are learning to appreciate.

Until recently, little was known about how normal human brains change as they grow, because conventional medical imaging techniques were too dangerous, invasive or uncomfortable for children, experts said.

The changing view of neural development is the brainchild of newer, less demanding brain imaging devices, such as functional Magnetic Resonance Imaging machines, called fMRIs, which can detect subtle physical changes associated with mental activity.

“A lot of people think of the child’s brain as a miniature version of the adult brain,” Casey said.

The new scanning techniques are revolutionizing ideas about childhood development. “You are seeing a ripe brain that is really forming itself right there in front of you,” she said.

In the study, researchers at Washington University in St. Louis combined fMRI brain scanning and simple word tasks to probe for differences in the way brains work.

They tested 19 children using simple word tests that required participants to say a word in response to a written word, like a rhyming couplet or the word’s opposite. Those images then were compared to those brain scans of 22 adults who took the same test.

The images revealed which brain regions were actively involved in different tasks. The study highlighted two brain regions in the left frontal and left rear cortices, which are known to play a key role in language processing. They also are thought to change considerably between childhood and adulthood.

The researchers found that children between the ages of 7 and 10 did not use their brains in quite the same way as adults performing the same language tasks.

The contrasts could be seen across many neural areas, but were most noticeable in frontal brain regions associated with planning, memory and attention. Some of the difference could be attributed to skill and experience, while others clearly arose from age.

In essence, children’s brains seem fuzzy--more diffuse and unfocused in some key regions of neural activity. Brain regions necessary for crucial reading and language skills continue to develop well into the school years, the researchers reported.

“We found there are dozens of regions that differ between 7- to 10-year-olds and 18- to 35-year-old adults,” said pediatric brain specialist Bradley Schlaggar, who led the research team. “Depending on age, the brain uses different components and strategies to accomplish an identical level of performance.

“Our results strongly suggest that functional neuroanatomy is still developing during early school years,” Schlaggar said.

Elizabeth Bates, director of the Center for Research in Language at UC San Diego, called the research “extraordinarily important,” because the researchers were able to carefully document the interaction of age, experience and skill. It allows a clearer view of what changes can be attributed to age and what changes arise from the neural effects of experience.

“It has implications for developmental disorders and problems in reading,” Cornell’s Casey said.

Yale University language expert Paul Bloom viewed the new results more cautiously, saying that brain-scanning studies often revealed more to the eye than might actually be present.

In particular, he said, most studies of this kind are unable to distinguish whether variations between age groups reflect developmental differences or whether they simply reflect the fact that children don’t perform as well overall as adults.

Despite his reservations, Bloom said the Washington University research was “a case study of the neural effects of learning.”

“I think these really are different parts of the brain developing at different times for the same task.”

Schlaggar at Washington University said his group took particular care to ensure they did not confuse the effects of age with those neural changes caused by varying degrees of skill and expertise.

“You have this chicken-and-egg problem,” he said. “Is the difference you see representing a true difference in the way the brain of one group processes the information? Or is there the difference just because one group doesn’t do the task well?”

Mirella Dapretto at the Brain Mapping Center at UCLA said the work was important because the study took careful account of such issues in diagnosing how growth alters the way the brain works.