Adult and child brains perform tasks differently

Children activate different and more regions of their brains than adults when they perform word tasks, according to a School of Medicine study.

The researchers recently reported in the journal Cerebral Cortex that those changes in regional brain activity from childhood to adulthood may reflect more efficient use of the brain as it matures.

“Basically, when children accomplish these same tasks with performance levels comparable to the adults, they do so with a different set of brain regions; that is, a different functional neuroanatomy,” said principal investigator Bradley L. Schlaggar, M.D., Ph.D., assistant professor of neurology, of pediatrics, of neurobiology and of radiology.

To see how the functional neuroanatomy changes with age, Schlaggar, Steven E. Petersen, Ph.D., the James S. McDonnell Professor of Cognitive Neuroscience, professor of neurology, of radiology, of psychology and of neurobiology, and their colleagues scanned 95 people with functional magnetic resonance imaging (fMRI).

Inside the scanner, study participants, ages 7-32, performed three word-generating tasks: rhymes (say “cat” in response to “hat”), opposites (say “up” in response to “down”) and verb generation (say “drive” in response to “car”).

As participants saw or heard a test word and spoke the correct response, an fMRI scanner took snapshots of their brain activity. The scanner detects changes in blood oxygenation levels that correlate with local changes in the brain’s activity.

Children and adults were compared according to performance level, defined by the number of correct answers and the time it took to complete a word task. Then, the researchers compared the fMRI snapshots of children and adults who were similarly good at the three tasks.

Brain activity varied between people of different ages, even though they were performing the same tasks at a similar level of proficiency.

Relative to adults, children tended to use more regions of their brains to complete the word tasks, activating more regions near the back of the brain. At the same time, children showed less activation in some regions at the front of the brain, which have been commonly seen in adult studies of word processing.

In some brain regions, children and adults showed very similar levels of activation while performing the tasks. This included some parts of the frontal lobe.

“This is particularly interesting because research on structural brain development has suggested the frontal lobe is relatively slow to mature,” Schlaggar said.

Because of this protracted development, many experts thought children didn’t use their frontal lobes like adults. But, this research suggests that large areas of the frontal lobe function similarly in children and adults when performing these tasks.

“We were surprised by the locations of many of the similarities and differences,” said first author and graduate student Tim Brown.

“We found that a few brain regions get more active, many get less active and some appear to stay the same across these ages.”

Brown said they also found preliminary evidence suggesting, for these tasks, some regions at the front of the brain mature earlier than some at the back.

That also was unexpected because of earlier structural data.

These new observations are made possible by recent improvements in fMRI scanning.

In the earlier scanning method, the fMRI scanner took images for long periods of time, similar to leaving the shutter open on a camera.

Although researchers could detect brain activity, they could not discern how the brain reacted to a specific stimulus.

In the fMRI method used in this study, the scanner took a series of quick snapshots three seconds apart.

This allowed Schlaggar’s team to discern what parts of the brain were activated as it was stimulated by the word-generation tasks.

Importantly, it also allowed them to distinguish brain activity related to different levels of performance.

The University researchers hope their observations will help them to understand normal brain function in order to compare those baseline observations with the brain function seen in atypically developing children with Tourette Syndrome, cerebral palsy and other conditions that can interfere with normal cognitive development.