A new study by researchers at Washington University
shows that children and adults use their brains
differently when processing language.
Scientists
have long suspected that there are differences in the
way children's brains work. They learn languages faster
than adults and adapt easily to brain injuries such as
strokes that would devastate adults. On the other hand,
adults do better on language problems and solve them
faster than children do.
But until recently,
researchers had no way to see what causes those
differences. Now scientists who study brain development
are using a technique called functional MRI to peer into
the inner workings of both the adult and child brain to
see whether children really think differently or just
lack experience.
The answer could be important
for treating children with learning disabilities or
brain injuries. If children use their brains differently
from adults, studies on adult brains won't be very
useful in detecting and correcting defects in children,
scientists say.
Because children don't have the
same language skills as adults do, scientists have had
difficulty determining whether the functional
differences they see between adult and child brains are
due to changes in the brain's makeup or to poor
performance by the youngsters. Researchers studying
brain diseases often encounter the same sort of problems
when comparing patients to normal people. The Washington
University researchers, led by Dr. Bradley L. Schlaggar,
used some innovative techniques to find which
differences in brain activity are due to age, and which
are linked to performance.
The study, published
today in the journal Science, compared 19 children
between the ages of 7 and 10, with 21 adults - mostly
medical students and graduate students between 18 and 35
years old.
The researchers asked their child and
adult volunteers to read a word and then do a task such
as saying an action that would go with the word, a word
opposite in meaning, or a rhyme for the word. While the
volunteers were thinking, the researchers took pictures
of their brains using an MRI machine.
The
researchers used some statistical tricks that allowed
them to directly compare the brain functions of adults
with children who performed nearly as well on the
language tasks. That let the scientists separate
developmental differences from variations in language
skills between the two groups.
The brain images
reveal that children use a region in the back of the
brain called the left extrastriate cortex, when
processing language. The region is located in area where
visual information is processed. Adults tended to have
much less activity in the extrastriate cortex and more
activity in a region called the frontal cortex. This
part of the brain seems to be involved in coordinating
many different parts of the brain, Schlaggar said.
The results could mean that children use a more
visual approach to language than adults do, Schlaggar
said. Another possibility is that other parts of the
brain may take control in children's brains until the
frontal cortex matures, he said. More research will be
needed to determine the answer.
Other
differences between the adults' brains and those of the
children were more likely to be associated with
performance, Schlaggar said. Children tend to have more
activity in all parts of the brain, while adults
concentrate tasks in particular brain regions, he said.
The study is the "gold standard" for the way
brain development research in children should be
conducted, said B.J. Casey, a cognitive neuroscientist
at the Sackler Institute for Developmental Psychobiology
at Cornell University.
The public often thinks
that scientists already know how the human brain changes
over time, but most of what we know is extrapolated from
animal research, Casey said. The first studies to
examine human children with functional MRI was published
in 1995, she said.
"Probably the most exciting
component of this study is what it's going to lead to
next," Casey said.
Data such as that Schlaggar
and his colleagues have collected on normal children
will be an important tool for evaluating children with
reading problems or brain injuries, Casey said. Such
studies will also be useful in determining whether
therapies restore normal brain function appropriate to a
child's age - something that studies on adult brains
can't determine, she said.
Reporter Tina
Hesman
E-mail: thesman@post-dispatch.com
Phone:
314-340-8325
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