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Deaf 'Hear' Vibrations

Study finds sensations activate auditory area of brain in deaf people

THURSDAY, Dec. 6, 2001 (HealthDayNews) -- Deaf people feel vibrations in the same part of the brain that processes sound information in hearing people, a new study shows.

By using functional magnetic resonance imaging (fMRI), University of Washington researchers discovered that vibrations activate the auditory cortex in deaf people.

"Because there is an absence of sound information, it appears the auditory cortex is used for processing information from vibrations," lead author Dr. Dean Shibata says. "Deaf people may perceive the vibrations in much the same way hearing people process sound. The vibrations probably feel quite different to deaf people than they do to hearing people."

Shibata and his colleagues used fMRI to see what would happen in the brains of 10 deaf and 11 hearing people. The test measures blood flow to different areas of the brain, and it shows doctors which parts of the brain are activated when a person performs a specific task.

For this test, the researchers had each person hold on to a plastic pipe that was set to vibrate intermittently. When the pipe vibrated, both groups showed activity in the part of the brain used to process touch information. But the deaf people also showed activity in their auditory cortex, Shibata says.

Knowing that a deaf person's brain rewires itself to perceive vibrations in the auditory cortex is important for two reasons, Shibata says.

Doctors operating for brain tumors or seizures on deaf people can't assume their brains work the same way as hearing people's brains do, he says. Surgeons need to know the auditory cortex may play an important role in helping the deaf process sound information, and they should be careful when operating around this area.

This study also suggests that tactile hearing aids and other electronic devices that help the deaf feel sound may be more useful than previously thought, particularly if they're used in the early years when the brain is developing rapidly, he adds.

But Dr. Susan Waldzman, co-director of the New York University Cochlear Implant Center, cautions against reading too much into the findings.

"Seeing activation on fMRI doesn't necessarily translate into function," she says. However, she adds that, in her own studies, she has learned the auditory system is more adaptable than was previously thought.

Shibata presented his findings at the recent Radiological Society of North America Scientific Assembly and Annual Meeting in Chicago.

What To Do

To learn more about how human hearing works, go to HowStuffWorks.com.

For more information about tactile hearing aids, go to the University of Exeter.

SOURCES: Interviews with Dean Shibata, M.D., assistant professor, medicine, University of Washington, Seattle; Susan Waldzman, M.D., professor, department of otolaryngology, New York University School of Medicine, and co-director, New York University Cochlear Implant Center, New York City; Nov. 27, 2001, presentation, Radiological Society of North American Scientific Assembly and Annual Meeting, Chicago
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