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Deafness givin’ them good vibrations

by Rowan Hooper

The Italians got it right about some of the important things in life, like olive oil and coffee. But they got it right about something else, too, something that brain researchers have only just realized. The Italian for “to hear,” sentire, is the same (in its reflexive form) as the verb “to touch,” (sentirse). In Italian, at least, there is no special distinction between hearing and touching.

Scottish musician Evelyn Glennie knows instinctively that this is true. Glennie has the distinction of being the only solo percussionist in the field of classical music. She is also profoundly deaf, meaning that she can hear, but the sound quality her brain perceives is not good enough to allow her to understand the spoken word. Hearing, she says, is nothing more than a specialized form of the sense of touch — the touch of air on your eardrums.

Radiologists and researchers into deafness now have more reason to agree with Glennie (and with the instictive link implicit in Italian). Earlier this week, researchers met in Chicago at the 87th Scientific Assembly and Annual Meeting of the Radiological Society of North America. There, Dean Shibata, assistant professor of radiology at the University of Washington, told them that the brains of deaf people become rewired to enable them to process vibrations like hearing people process sound. Shibata’s findings explain how deaf people can “hear” music at concerts and might even explain how Beethoven, famously deaf by the time he composed his greatest works, could have sensed his music.

Shibata used functional magnetic resonance imaging to compare brain activity between 10 deaf volunteers from the National Technical Institute of the Deaf at the Rochester Institute of Technology, and 11 volunteers with normal hearing. While the subjects were having their brains scanned, Shibata transmitted sequences of vibrations onto their hands.

In both sets of volunteers, there were bursts of brain activity in the part of the brain that processes vibrations. But the deaf students also showed brain activity in the auditory cortex, a golf ball-size area usually only active when people hear things. The volunteers with normal hearing did not show such brain activity.

“These findings suggest that the experience deaf people have when feeling music is similar to the experience other people have when hearing music,” said Shibata, who conducted the research at the University of Rochester School of Medicine in New York. “The perception of the musical vibrations by the deaf is likely every bit as real as the equivalent sounds, since they are ultimately processed in the same part of the brain.”

At the National Technical Institute of the Deaf, students attending musical productions are given balloons which amplify the music. The students hold onto the balloons with their fingertips in order to “feel” the music. Musical productions are an important part of deaf culture at the college; Shibata’s work might explain how some deaf people can enjoy music and how some, like Glennie, even become performers.

“Vibrational information has essentially the same features as sound information, so it makes sense that in the deaf, one modality may replace the other modality in the same processing area of the brain,” said Shibata in his paper. “It’s the nature of the information, not the modality of the information, that seems to be important to the developing brain.”

The brains of children are incredibly flexible and adaptive. Shibata’s work suggests that it might be worth exposing deaf children to music as soon as possible, to encourage the brain’s “music centers” to develop. Tactile aids similar to the balloons held by students watching musicals at the National Technical Institute of the Deaf, have been made to assist verbal communication.

“These findings illustrate how altered experience can affect brain organization. It was once thought that brains were just hard-wired at birth, and that particular areas of the brain always did one function, no matter what else happened,” Shibata said. “It turns out that, fortunately, our genes do not directly dictate the wiring of our brains. Our genes do provide a developmental strategy — all parts of the brain will be used to maximal efficiency.”

It’s a sentiment that Glennie understands well. “To understand the nature of deafness,” she says, “one first has to understand the nature of hearing.”

And that means understanding the nature of the brain — no easy feat. MRI technology is helping us do it, and is showing that the brian is more complex and flexible than we used to think — as might be expected from the organ that remains our last great biological mystery.