SOUNDING OUT THE SECRETS OF HEARING
To the casual observer, two women chatting about college life hardly qualifies as a miracle. Except that both are deaf and neither is using sign language.
Look closer and you’ll see that Nanci Linke-Ellis and Elizabeth Yazbek each wear a coin-sized device behind one ear. The crescent-shaped piece of plastic could be mistaken for a hands-free cell phone or MP3 ear bud. But this sound machine does much more.
Functioning as a translator of sorts, the cochlear implant both women wear helps them converse in a way that, to an outsider, looks like two hearing people talking. The device, parts of which are embedded under the skin, distills the ebb and flow of their voices into electric signals. These pulses then bypass the lifeless areas of their inner ear and stimulate the hearing nerves that still function, which in turn feed the sound signals to the brain.
Once in the brain, these pulses are somehow reassembled – scientists aren’t quite sure just how – into something akin to speech, though a person with normal hearing wouldn’t recognize it.
The device performs this intricate electronic relay in real time, and its key component, the speech-processing computer in the earpiece, weighs less than an ounce.
For Linke-Ellis, an OHIO alumna, the inner workings of this electronic marvel are overshadowed by what it enables her to do. With her implant, she can hear her husband talk and even pick up dialog from a movie. A 1971 graduate with a bachelor’s in fine arts, she heads a nonprofit organization called InSight Cinema that helps bring the big-screen experience to moviegoers with hearing challenges.
She is visiting her alma mater on this spring afternoon to urge students of hearing, speech and language science to champion the rights of their future patients. With an almost evangelistic zeal, she describes to Yazbek and the other students the challenges she had to overcome as a deaf student at OHIO in the late ‘60s. It meant hustling to the front of classes to lip-read lectures; relying on friends to jostle her awake in time for classes, since an alarm clock or telephone would not wake her.
Linke-Ellis made it through those years and forged a successful career as an executive in the television and motion picture industries. She succeeded through “bluff and barter,” masking her deafness and relying on her prodigious lip-reading skills. She would type up a co-worker’s notes, say, if they’d agree to make a phone call for her.
“There were no [support] groups,” Linke-Ellis said. “There were no resources to help people with advocacy. … I grew up without Disney.”
The social landscape has changed since then, with passage of the Americans with Disabilities Act of 1990 and the growth of advocacy groups for people with physical challenges. At OHIO, a group of students – Yazbek among them – formed the Sign Language Club in spring 2006 as a way of building a bridge between those who hear and those who can’t.
Even more dramatic changes have come on the technological front, in the rapidly advancing field of cochlear implantation. During Linke-Ellis’ college days, there were no implants. When they began appearing in the early ‘80s, the relatively primitive devices were little more than bulky curiosities that could detect a few sounds and assist with lip-reading. Today, the sleek, behind-the-ear models worn by Linke-Ellis and Yazbek enable them and many of the 70,000 other implant users to hold a phone conversation.
As the technology advances, the volume of implant-related research has also grown steadily – much of it originating from OHIO’s School of Hearing, Speech and Language Sciences. More and more, studies show that cochlear implants can be pivotal in helping deaf people to acquire or retain speaking skills, especially young children. In the most successful cases, children fitted with implants before age 2 have developed language skills on par with their hearing peers.
Cochlear implants function differently than hearing aids, which merely amplify sound. Implants, prescribed only for profoundly deaf people, serve as a sort of hearing surrogate, re-interpreting sounds for the brain that normally would be transmitted by the delicate array of bones, membranes and hair cells of the inner ear.
Implants are also far more expensive than hearing aids. The cost of evaluation, surgery, the device itself and rehabilitation can reach $75,000. Yet the devices have made the leap from novel technology to mainstream medicine, as most insurance companies now routinely cover the procedure, provided that a patient’s hearing falls below certain performance levels.
Linke-Ellis was fitted with hers in 1993, soon after she lost the last trace of her hearing. To ensure maximum success with an implant, a patient with some hearing must receive the device soon after a total hearing loss, before the brain and auditory nerves “forget” what to do with sound.
“For me, [the cochlear implant] was life-altering because it allowed me to do things I’d never been able to do before,” she said.
Fine-tuning the instrument
Despite the seemingly miraculous outcomes for implant users such as Linke-Ellis, the devices are fraught with limitations. They can’t decipher music, and at best they provide only an approximation of human speech – often described as a Donald Duck-like series of squawks. They are effective only in quiet environments. And perhaps most troublesome, there is no reliable predictor of how well an implant patient will perform with the device, since success depends on variable factors such as the degree of auditory nerve loss.
Nor can current models reliably process tonal languages, spoken by more than a quarter of the world’s population. Tonal languages are typically more difficult to master than English because the pitch used to pronounce a word determines its meaning. So the same syllable can have different meanings, depending on how the speaker says it. The speech processors in the current generation of cochlear implants, though infinitely more advanced than those of 10 years ago, simply aren’t capable of picking up such nuances.
That’s where the pioneering research of a pair of OHIO audiology professors comes in. Li Xu and Fuh-Cherng Jeng are hoping their work will help “teach” cochlear implants how to convey auditory details like the verve of a violin concerto and the tonal difference between “Ready?” and “Ready.”
Xu is an associate professor in the College of Health and Human Services’ School of Hearing, Speech and Language Sciences. Slightly built and soft spoken in person, Xu’s research on cochlear implantation is respected internationally. Much of his research been funded by a grant from the National Institute of Deafness and Communicative Disorders, part of the National Institutes of Health.
In the last few years, he’s written extensively on tone recognition among implant users, and has been a featured speaker at international conferences in South Korea, Russia, Taiwan, France, Finland and the Netherlands. At the moment, he’s collaborating on a study involving China’s Beijing Tongren Hospital that focuses on tone perception and speech performance among children fitted with implants.
Hearing loss is particularly a problem in China, he said, due to the widespread use of an inexpensive antibiotic called gentamicin, which can damage the sound-sensing hair cells of the inner ear. Nearly 21 million Chinese have at least some hearing loss, according to the advocacy group China Disabled Persons’ Federation.
Xu focuses on finding the best methods for an implant’s speech processor to divide sound into enough layers, or channels, so that the subtleties of the human voice aren’t lost by the time they reach the brain.
Despite the limitations of today’s cochlear implants and the years of research ahead to fine-tune them, Xu marvels at how empowering the devices can be for someone like Nanci Linke-Ellis.
“It is a miracle.”
Complementing Xu’s efforts is the work of his colleague, Jeng, an assistant professor who joined OHIO in fall 2006. Jeng works to map how and where the brain responds when it receives voice signals. He is setting up a lab in Grover Center for his testing, and he hopes to have the facility operating in early 2007.
Participants in his research will listen to speech while wearing an electrode-studded head covering that resembles a swimming cap. His equipment will scan the listener’s brain for responses. On a nearby monitor, Jeng will study a three-dimensional image of the participant’s brain as different areas light up, indicating a response. He speculates that there will be different responses to a speech sound whose tone is altered slightly. He offers an example.
“I love you.”
“I love you.”
Research is thin on how the brain reacts to such modulations, Jeng says, but it’s this mapping that may hold the key to bringing music and tonal languages into the non-hearing world.
“The [cochlear implant] procedure itself is not the main issue,” Jeng says. “The main issue is, ‘Do you really understand how it works and how the auditory system works, and how do we mesh the two for maximum performance?’ ”
Coming to OHIO has allowed him to fulfill his dream of continuing research in this area. When asked what drew him to study this field, the researcher’s voice softens.
“Imagine one day when you find somebody you care for. You want to say something important. You want your information to be modulated with human speech, with music, with your emotion.”
Big help for little voices
Cochlear implants have had a profound impact on many of the 20,000 or so deaf children who have received them. In 2002, the U.S. Food and Drug Administration approved the use of implants for children as young as a year old.
Pam Reese is a clinical supervisor at Ohio University Therapy Associates, the speech, hearing, language and physical therapy clinic in Grover Center. She has worked with young children after they received an implant, and she says watching a deaf child hear for the first time is unforgettable.
“You see a pause, a look in the eye, and the head turns and you realize, ‘He heard it.’ ”
Maria Sentelik is founder and executive director of Ohio Valley Voices, a Cincinnati-area school that teaches deaf youngsters to talk and understand speech. The goal at Ohio Valley Voices, whose charges range from 18 months to second grade, is preparing deaf youngsters to attend school with their hearing peers.
Of the 40 currently enrolled, 38 have cochlear implants. Sentelik said the children blossom as they learn oral skills. Sign language, while helpful, she says, has limitations in the hearing world. Since most hearing people don’t sign, she said, signing can be isolating if not combined with oral-aural communication.
“With the implants,” Sentelik said, “we’re able to have children who can communicate however they want. You give them a cochlear implant, you teach them to talk and the world is their oyster.”
She has seen the successes. She describes a girl who attended the school who had been fitted with an implant at 18 months old. The youngster is now in a public school gifted program.
Sentelik believes such success stories never would have been possible two decades ago. Before cochlear implants and their ability to help deaf children speak and engage in the hearing world, most were pushed to society’s margins.
“You would have never recognized who they were or what they would be able to offer us,” she said. “Now they can contribute to society and express their ideas and attain whatever they want.”
-- Article by Jody Grenert, College of Health and Human Services communication director.