NEW YORK, N.Y., July 10, 1997 ‹ In a study that sheds new light on how the brain organizes language, researchers at Memorial Sloan-Kettering Cancer Center report in the July 10 issue of the British journal Nature that the organization of the brain's language-production region in bilingual individuals is directly related to whether they learned a second language as toddlers (simultaneously with their native language) or as young adults. Using a new, non-invasive imaging method called functional magnetic resonance imaging (fMRI), the researchers found that bilingual persons who acquire a second language as young adults have distinct areas in the brain associated with their native and second languages.
"A second language acquired during the teenage years, which is late in developmental life, is represented in the brain in a separate location from the native language," explains senior author Joy Hirsch, Ph.D., head of Memorial Sloan-Kettering's fMRI Laboratory. "But when both languages are learned at the same time early in life, they are represented in areas that have a considerable amount of overlap." The study also highlights the promise of fMRI to precisely map the language centers of the brain. This information may be useful to neurosurgeons who, during surgery to remove a brain tumor, must carefully navigate their scalpels around the brain's language-sensitive areas to avoid damaging a patient's ability to speak. About 25 percent of brain tumors occur near the region of the brain that controls language production, called Broca's area. Until now, imaging technology has lacked the ability to produce high-resolution maps of the brains of individual patients.
Dr. Hirsch and lead author Karl Kim, a Memorial Sloan-Kettering neuroscience graduate student, are now evaluating the utility of fMRI to map the language, motor, and sensory regions of patients' brains prior to surgery to remove a tumor. "Based on the results of the current study, we always ask our patients whether they speak more than one language," Kim said. "If they do, both languages need to be mapped to acquire a complete picture of language-sensitive brain regions."
So far, MSKCC researchers and physicians have found that fMRI makes it easier for physicians to pinpoint the exact site of language-sensitive brain regions so patients can emerge from surgery without loss of function.
Of the 12 bilingual participants in the current study, half had learned two languages simultaneously as toddlers and half had learned a second language as teenagers. All were healthy and could speak two languages fluently. The participants were asked to perform silent speech tasks (to reduce head movement) in both languages so the researchers could image the activity in Broca's area.
Scientists and clinicians have long suspected that separate regions of the brain are involved in native and second languages based on reports in the medical literature of bilingual individuals who lost the ability to speak one language after removal of a brain tumor or after suffering a stroke or seizure. But the current study is the first to demonstrate the distinct spatial relationships in the brain between native and second languages, said Dr. Hirsch.
The fMRI laboratory at Memorial Sloan-Kettering is now applying recently developed fMRI techniques to test critical hypotheses about the workings of the brain, and to develop new methods to provide adjuvant guides for neurosurgical procedures.
Memorial Sloan-Kettering Cancer Center is the world's oldest and largest private institution devoted to prevention, patient care, research, and education in cancer. Throughout its long, distinguished history, the Center has played a leadership role in defining the standard of care for patients with cancer. In 1996, Memorial Sloan-Kettering was named the nation's best cancer center for the fourth consecutive year by U.S. News & World Report.