Health & Science:  Study examines fluency in language
By LEE BOWMAN Scripps Howard News Service

The critical childhood window for becoming fluent in a language
applies to sign language as well as spoken language, according to a
new study.

Using functional magnetic resonance imaging, the researchers found
different patterns of brain activity in bilingual people who learned
American Sign Language before puberty and after puberty.

Language researchers have long known that children find it much easier
than adults, or even teenagers, to acquire a second language because
their brains have more connections between neurons. This makes for an
easier time incorporating the new language into their brain networks
and allows them to think in the language, rather than translate.

For the same reason, children who are not exposed to any language
before puberty, or even sooner, are unable to fully acquire and use
language because unused connections disappear as people age.

In the new study, reported Thursday in the January issue of Nature
Neuroscience , researchers studied brain images of 27 subjects - 16
who were hearing persons born to deaf parents who learned both sign
language and English as native languages and 11 "late learners" who
spoke English as a native language and learned sign language in early
adulthood.

The team, led by David Corina, a University of Washington associate
professor of psychology, had earlier found that parts of the right
hemisphere of the brain are needed to process American Sign Language,
along with the left hemisphere that is used in spoken language. Other
members of the team came from the University of Oregon, the University
of Rochester and John Radcliffe Hospital in England.

"One area of the brain that's the signature, or specific, to signers
if they learned ASL as a native signer is the right angular gyrus,"
Corina said. Activation of the left angular gyrus has been linked to
reading English and other spoken languages for years, but the new
study found that the right was consistently used by those who had
learned signing as a first language, but more sporadically by the late
signers.

"We know that late learners of ASL, while they are very fluent, never
will be fully fluent like native, or early learners of ASL," said
Corina, who is himself fluent in the sign language.

"One aspect of ASL that is difficult for late learners is verb signs
of motion. You see some subtle errors in their use of these verbs,
just as you might detect subtle grammatical differences when listening
to bilingual users of spoken language when they're not using their
native tongue," Corina said.

It appears that the difference in fluency for sign language lies in
the wiring of the right side, more than the left side, of the critical
brain regions, the researchers concluded.

"To see that this activation in the right hemisphere is dependent on
early exposure suggests there are specific times when neural systems
for language may be particularly sensitive to change," Carina said,
adding that the findings have implications for education and early
exposure to language of all children.

Copyright © 2002 Scripps Howard News Service
Copyright © 2002 Nando Media

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