I Can Hear You Whisper (15 page)

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In the Department of Speech, Language and Hearing Sciences at the University of Colorado at Boulder, auditory neuroscientist
Anu Sharma studies brain development in children with cochlear implants. It's work she began at Arizona State University with speech and hearing scientist Michael Dorman, who started working on cochlear implants in the 1980s. In order to assess how well a brain is making use of the sensory input it receives, Sharma focuses on how long it takes the brain to react to sound. The speed of that reaction is a measurement of synaptic development. Sharma, too, uses EEG, looking particularly at what is known as the cortical auditory evoked potential (CAEP for short), the response to sound beyond the brain stem in the auditory cortex.

Studying the waveform that is generated by the test, Sharma looks for the first big fall and rise of the line: The first valley is known as P1 (first positivity), and the adjacent peak is N1 (first negativity). The upward slope of the line connecting those two points roughly indicates the speed at which two parts of the brain—primary cortex and higher order cortex—are communicating. Sitting in her office in Boulder with a view of the Rocky Mountains behind her, Sharma demonstrates by holding out her fist to represent the primary cortex, then wrapping her other hand over the top of her fist to show the higher order cortex (the outer layer of the brain). “They need to connect; they need to talk,” she says.

In typically developing hearing children, that connection in the brain starts slowly and then speeds up. Latency is the time it takes in milliseconds for the brain to react to a sound. In a newborn the latency of the P1 response might be three hundred milliseconds; in a three-year-old, it has dropped to one hundred twenty-five milliseconds. As a child grows, that time continues to shorten. With age and experience, the brain becomes more efficient. By adulthood, P1 latency is down to sixty milliseconds.

In children with cochlear implants, Sharma found that being implanted early makes all the difference in terms of how much help the child will get from the implant. The peak of synaptic activity in the auditory cortex is when a child is three and a half, says Sharma. Experience prunes and refines synapses allowing learning to occur. Those that are getting used stay; those that are not are pruned away. “Hearing helps to prune them,” she explains. “If a child gets the implant under the age of three and a half, that part of the brain looks quite similar to that of a normal hearing child. If they wait until they are seven or older [or had been deaf for more than seven years], the hearing part of the brain of the implanted child never looks the same.” Between the ages of three and seven, the studies showed a range of responses, but earlier was almost always better. Sharma and her colleagues had identified sensitive periods for hearing and brain development.

“We looked more closely and found that what happens after the sensitive period closes is the brain gets reorganized,” she says. “That's important real estate. If sound is not going in, it's not going to sit there waiting forever.” In some of the secondary areas, for instance, vision and touch take over. “That's how the brain changes in deafness.”

No wonder Dr. Parisier was in a hurry.

O
n a sunny spring day in 1966,
Graeme Clark, a young Australian ear, nose, and throat surgeon, had a little extra time for lunch and decided to eat outside on a park bench. He was shuttling between jobs at various hospitals in Melbourne, so he carried a lot with him, including a backlog of scientific and medical journals. He pulled one out and found a report by Blair Simmons on achieving some hearing sensation, though no speech, from the six-channel device they had implanted in Anthony Vierra. Just like that, Clark knew what he was going to do with the rest of his life. “That lit that research fire in the belly,” he says. “It all became clear.”

We were sitting around a table at the Royal Victorian Eye and Ear Hospital in Melbourne. For some thirty-five years until his retirement in 2004, this had been Clark's office. It was here, about as far from the medical centers of Europe and America as it is physically possible to be, that Clark assembled a team of young researchers to build a viable multichannel cochlear implant. Research groups at the University of California, San Francisco (
UCSF), and at the University of Utah as well as in Paris and Vienna were pursuing the same goal. (Bill House was still using his single-channel device and Blair Simmons, who died in 1998, got less involved over time.) At the start, the idea that Clark's group could achieve such an ambitious goal was almost laughable. They had no money, little prestige, and, at times, no patients. Today, many of those same audiologists, engineers, and scientists are still in Melbourne, running the various spin-off clinical and research organizations that grew out of Clark's efforts.

A thoughtful, deeply religious man, Clark shares the formality of his generation. In a country where men have been wearing shorts to work for decades, he is often in a jacket and tie, as he was when we met at the hospital. Earlier in his career, at a dinner in his honor,
a colleague joked that he had wanted to entertain the crowd with tales of Clark's youthful indiscretions but hadn't been able to find any. From a young age, Graeme Clark was apparently remarkably single-minded.

He was born in 1935 in Camden, then a small country town some forty miles from Sydney. His father, Colin, was a pharmacist and ran a chemist shop in town. Around the age of twenty, Colin Clark began to lose his hearing, and it got progressively worse throughout the rest of his life. There could be uncomfortable consequences from the combination of hearing loss and a pharmacy. “People had to speak up to say what they wanted,” remembers Graeme Clark. “It was embarrassing when someone came in to ask for women's products or men's products, contraceptives or the like.” As a boy of about ten helping out in the shop, Graeme would have to find the requested item. “I didn't know much about the facts of life, but I knew where [things were in the shop],” he says with a laugh. Later in life, Clark asked his father about his experience of hearing loss. “He said it was terrible,” Clark remembers. “It was a struggle to hear people at work and social environments with background noise. He would be tired out through having to listen so hard and make conversation.” Clark's childhood sense of lost opportunity was strong. “[My father] was quite a sociable person. He could have been president of the [local social] club, but he couldn't manage those things. He'd sit in the corner sometimes of the lounge room when we'd have visitors, and they would think he was dumb.”

Life in his father's chemist shop exposed Clark not just to deafness but also to medicine. He got to know the local doctors, and the idea of helping people appealed to him. As early as kindergarten, he told his teacher he wanted “to fix ears” when he grew up. He repeated that to the family's minister when he was ten. By sixteen, he was studying medicine at the University of Sydney. By twenty-nine, he was a consultant surgeon, still so boyish in appearance a nurse once refused to let him in to visit his own patient.

But medicine alone wasn't enough. Clark always nursed an interest in research, believing that a man with both clinical and laboratory experience could be most effective and most aware of what was needed. Blair Simmons's report gave Clark the research direction he'd been missing, one that aligned perfectly with his childhood mission of “fixing ears.” He knew Bill House had already operated on a few patients as well, but Clark hewed closer to Simmons's methodical approach. In order to see “what the science would show,” he left his flourishing surgical practice to pursue a PhD in auditory physiology, studying electrical stimulation in the auditory system of cats. “It was a complete gamble,” he says. “Ninety-nine percent of people said it wouldn't work.” Clark and his wife, Margaret, had two children at the time and would go on to have three more. As a doctoral student, he made so much less than he had as a surgeon that when their old car broke down, they couldn't replace it. “But those were some of the happiest times in our lives because I wasn't in the rat race,” he remembers. “And because research was exciting.”

With his doctorate in hand, Clark got lucky. A position as chair of the Department of Otolaryngology opened up at the University of Melbourne and the Royal Victorian Eye and Ear Hospital. As Clark worked to assemble a team there, he was raising money with one hand—literally shaking a can on street corners at times as part of fund-raising efforts—and doling out the cash carefully to his young staff with the other. Everyone worked from one three-month contract to the next. “I was young and they were younger,” he says. Like Simmons, Clark believed he would need a multidisciplinary team to provide expertise on the considerable variety of jobs required to create this piece of technology. Over the years, he employed engineers, animal researchers, audiologists, computer programmers, speech scientists, and surgeons.

For most of the 1970s, Clark's group labored over a workable prototype of a multichannel device he called a “bionic ear.” The solution to
one particularly stubborn surgical question—how to insert the device safely and fully into the snail-shaped cochlea—came to Clark during a vacation. While his children played on the beach, he collected a series of spiral-shaped shells and a variety of grasses and twigs, and tried to stuff the grasses through the shells. He discovered that materials that were stiff at one end and flexible at the other worked perfectly. In the lab, his team created an electrode bundle that mimicked the grasses he'd found—stiff at the base but increasingly flexible toward the tip. Other challenges included reducing the necessary circuits from an
original diagram wider and higher than a grown man's torso to a tiny silicon chip.

The resulting device looked as homemade as it was. Bigger, lumpier, and less refined than the corporate versions that followed, the implanted piece consisted of a gold box a few centimeters square containing the electronics to receive signals and stimulate the internal electrodes. The electrodes were attached to the stimulator by a connector so that in the event of a failure, only the gold box would have to be replaced, not the electrodes in the inner ear. The whole package was encased in silicone to protect against corrosive bodily fluids.

But they still had to figure out what signals to send through this new device. “The way sound stimulates the inner ear is different from the way in which electrical currents stimulate the nerves,” explains Clark. “When you put electrical current into the nerves, it tends to stimulate them all at one time.” The answers wouldn't really come until after they had implanted their first patient.

That was another problem. They needed patients, and they didn't have any. Because of the fund-raising campaign, which included telethons, the public profile of their work was high. But doctors who saw patients refused to refer anyone. They thought Clark had overstated what was achievable. “I think I said there would be about five thousand people in Australia who could benefit from a cochlear implant,” says Clark with a laugh. In fact, he understated the eventual demand by several orders of magnitude—an estimated
320,000 people use them worldwide today. But at the time, in Australia as in the United States, the response in medical and scientific circles was skeptical.

Clark was getting desperate until he met a forty-eight-year-old man named
Rod Saunders who had been visiting the deafness unit in Clark's own hospital. Saunders had lost his hearing in a car accident twelve months earlier, when lumber he was carrying in his car—precariously jammed between the seats—smashed into his head when he collided with a light pole. His injuries left him completely deaf in both ears. He had seen Clark's project in the news. When he came in for an appointment one day, he asked at the front desk whether he could see Professor Clark. “No,” he was told. “We don't recommend it.” Standing within earshot, however, was an audiologist named Angela Marshall, who was spending some of her time in Clark's laboratory. She pulled Saunders and his wife aside and said she could help. As Clark puts it, “Angela smuggled Rod up.”

The second patient,
George Watson, managed to get to Clark directly. He was a World War II veteran and had been profoundly deaf for thirteen years after losing his hearing progressively following a bomb blast. Both Saunders and Watson felt they had little to lose, and both found their deafness debilitating. Saunders, who couldn't speech-read well at all, called it a “nightmare.” He told Clark what he missed most was hearing the voices of his family. “I miss music,” he said. “I even miss the sound of the dog barking.” Watson described his feeling of isolation. “You feel completely alone,” he said. “I mean you go to a football match, people cheering and so forth, or you go to a race meeting, but it is all so very even all the time. . . . Actually, it is very boring. Everything is the same, nothing seems to alter.” Even these conversations with Clark were awkward, requiring a combination of speechreading and written questions.

“We were really fortunate with the first two guys,” says Richard Dowell, who today heads the University of Melbourne's Department of Audiology and Speech Pathology but in the late 1970s was a twenty-two-year-old audiologist working for Clark on perception testing with Saunders and Watson. “They were both sort of laconic characters, not too fussed about anything. They had to go through a lot of boring stuff and things didn't [always] go right. They were basically guys who'd put up with anything and continue to keep coming in and support the work. They didn't necessarily want anything out of it for themselves.”

Clark decided to implant Rod Saunders first and scheduled surgery for August 1, 1978. He and the surgeon who would assist him, Brian Pyman, had repeatedly rehearsed the steps of the operation on human temporal bones from the morgue. When he could practice no more, Clark went away with Margaret for a prayer weekend. The operation lasted more than eight hours. As Saunders recovered that night in the ward, Clark called the night nurse every few hours to check on his condition, but all was well. Saunders went home after a week.

Three weeks later—enough time for the surgical wound to heal—Saunders returned to the hospital to have the prosthesis turned on. They put the external coil in position and turned on the electrical current, gradually increasing its strength.

It didn't work.

“Rod, do you hear any sound?” Clark asked.

Saunders was listening intently, but he answered dejectedly. “I'm sorry. I can only hear the hissing noises in my head.”

Depressed and worried, Clark and his colleagues had to send Saunders home. When he returned a few days later, results were no better. There were several sleepless nights for Clark. Finally, before Saunders's third appointment, engineer Jim Patrick discovered a fault in the test equipment and repaired it—to everyone's relief. “We approached the next session with great anticipation,” remembered Clark.

This time Saunders heard sounds. Each of the electrodes was tested and they were all working. The sounds were limited, but a cause for celebration nonetheless. Clark and Pyman took the surgical nurses and their spouses out for a Chinese dinner to mark the occasion.

At the next session, they wanted to know whether Saunders could recognize voicing and the rhythm of speech. They used the computer to play songs through the implant, beginning with the Australian national anthem, “God Save the Queen.” Immediately, Saunders stood to attention, pulling out the wires connecting him to the computer when he did. Everyone laughed with relief. Then someone suggested they try “Waltzing Matilda.” Saunders recognized that as well. It was solid progress, but Saunders still couldn't understand speech and he didn't seem to be recognizing different pitches. The design of this device was predicated on the idea that multiple electrodes laid out along the cochlea would deliver variations in frequency that would enable users to hear the sounds of words. But Saunders described the different signals he was hearing as “sharp” at high frequencies and “dull” at the low end, but not higher or lower than one another. “The sensations were changing in timbre, not pitch,” explains Clark. He couldn't help but wonder: “Have we gone to all the trouble to produce a multichannel system . . . and it didn't work?”

An engineer named Jo Tong was one of Clark's closest collaborators in those early days, and Tong had taken the lead in designing the speech processing program that determined the instructions sent into the new device. He and Clark began with the belief that the cochlear implant had to try to reproduce nearly everything that goes on in a normal cochlea. Like a glass prism breaking up light into all the colors of the rainbow, the cochlea takes a complicated sound such as speech and breaks it into its component frequencies. The internal electrodes of the implant were designed to run along the cochlea, mimicking the natural sequence of frequencies. Clark's team was betting that the
place
that was stimulated was critical to delivering pitch to the user, and pitch was critical to understanding speech. Initially, Tong designed a processing program that stimulated every electrode, on the theory that all parts of your basilar membrane are perceiving sound at once in normal hearing and that the appropriate areas would react more strongly to the appropriate frequencies. But since electrical stimulation is far less subtle than the workings of a normal cochlea, the result had proved incomprehensible.