Published online 27 November 2001 | Nature | doi:10.1038/news011129-10

News

Feel the music

Deaf people use 'mind's ear' to process vibrations.

Good vibrations: deaf peoples' brains rewire themselves.Good vibrations: deaf peoples' brains rewire themselves.© Photodisc

After going deaf, Beethoven sawed the legs off his piano and played it on the floor so he could feel its vibrations. Nearly two centuries later, brain imaging is revealing that deaf people may 'hear' vibrations just like others hear sounds - using the auditory centres of the brain.

When holding a vibrating plastic pipe, people born deaf have brain activity in the auditory cortex, but those with normal hearing don't, says Dean Shibata of the University of Washington. Shibata presented his findings on 27 November at the Scientific Assembly and Annual Meeting of the Radiological Society of North America in Chicago.

The study suggests that the brain of a deaf person rewires itself to process vibrations in the absence of sound. It may be that deaf people experience vibrations in the same way that hearing people experience sound, says Ruth Campbell of University College London, UK, who studies how deaf people communicate. "Is it like hearing? This opens the question up," she says.

The findings may explain why many people who have never heard a sound appreciate music, Shibata says. "Deaf people like to dance and can sense melodies and rhythms," he says. "It's not clear what they perceive, but it's clear that they enjoy it." Concerts at which deaf people hold balloons to amplify vibrations have been great successes, he adds. Research earlier this year found that that deaf people are more sensitive than hearing people to minute changes in vibration frequencies. "This sensitivity might have developed to warn deaf people about dangers in the environment that they can't hear," says Sari Levanen of Massachusetts General Hospital, a member of the team who performed the study.

A deaf person's brain may convert the auditory cortex into a vibration-processing centre because the region is already well adapted to the task, thinks Levanen. "Physical vibrations and sound require similar information processing."

But it is also possible that the brain routes vibrations to the auditory cortex simply to make use of valuable brain real estate, says Ian Summers, a biomedical physicist at Exeter University, UK, who studies sensory perception.

After a limb is amputated, Summers says, the part of the brain that controls the limb's sensation is encroached upon by other brain regions. A patient touched on the nose may have the illusion of being touched on the missing limb, for example.

Regardless of what causes rewiring, says Shibata, his work suggests that deaf children may benefit from an early introduction to music while the rewiring is taking place.

Such early exposure could also help deaf people use 'vibro-tactile' devices that convert sound into vibrations to supplement lip-reading, Shibata suggests. Although the devices have been shown to be effective, many people find them hard to adapt to. "If people want to learn to use the devices, it's good to start early," Shibata says. 

  • References

    1. Levanen, S. et al. Feeling vibrations: enhanced tactile sensitivity in congenitally deaf adults. Neuroscience Letters 301, 75 - 77 (2001). | Article | ISI |