When people grow up bilingual, their brains process the two languages differently than when they acquire a second language in adulthood, according to a study based on images of the brain at work.
Using a technology called functional magnetic resonance imaging to show the brain at work, researchers found a difference between two types of bilingualism.
``Languages acquired late in life are actually stored in a different place than are languages that are acquired earlier in life,'' said Joy Hirsch, professor of neuroscience at Cornell University Medical College and senior author of the study, which is being published Thursday in the British journal Nature.
The research is part of a field known as neuro-imaging, in which scientists try to measure the brain at work.
Another researcher, Denise Klein, a cognitive psychologist at Montreal Neurological Institute at McGill University, welcomed the findings as ``quite interesting,'' but added that much more research is needed.
Klein used another technology, positron emission tomography, known as PET scans, to measure the brains of bilingual people, and found only one area of activity, no matter which language. Her 1995 study is not necessarily a contradiction of Thursday's report.
The study being released involved 12 people. Six learned two languages as toddlers; the other six learned a second language as teen-agers. They were shown pictures of morning, afternoon, or evening scenes and asked to ``speak'' to themselves a story about what they did during that time of day, in one of the two languages they knew. (Audible speech leads to too much head movement, compromising the MRI image.)
Among those who grew up bilingual, activity was noted in the same region of the part of the brain known as Broca's area.
But among those who learned a second language later, activity was noted in separate parts of the Broca's area, one for the native language, one for the later language.
In another language center of the brain, known as Wernicke's area, all study participants showed only one region of activity, no matter which language they used. Among the languages were Chinese, Croatian, English, German, Hebrew, Italian, and Spanish.
Broca's area, in the frontal lobe, is more involved in verbal production of language; Wernicke's area, in the temporal lobe, is more involved with understanding.
While scientists have long suspected that native and second languages involve different parts of the brain, based on reports of patients who lose the ability to speak one language after removal of a brain tumor or after a stroke, the study provides physiological evidence of such separation.
This research strikes a chord with anyone who has ever studied a language, but Hirsch said she and her cancer center colleagues also did the work as part of a plan to map the brain for language and other activities. Such mapping would give valuable preoperative information to neurosurgeons.
But for Canadian researcher Klein, who grew up in South Africa speaking Afrikaans and English, and later acquired French and Hebrew, the motive is more personal.
``Questions about bilingualism are interesting in themselves _
just how the brain works and how language is represented,'' Klein
said. ``Everybody wants to know how you can better learn a second
language.''