Five years ago, Saul Simon admits, he was at a low point.
Retired from a highly successful career in the clothing business, he’d lost both sight and hearing to a rare, progressive disease called Usher’s syndrome. That in turn meant other losses, including friendships.
The only way he could take in information, says the Needham, Mass., resident, was to have people print letters with a finger in the palm of his hand. “When you go out to dinner with friends, how many of them are going to want to print letters on your palm?” he says.
Urged on by his wife and children — the couple has three — Simon agreed to get an inner-ear device called a cochlear implant. He was dubious, and, as the time for his surgery neared, nervous. But he went ahead anyway.
After the prescribed healing time, Simon started hooking up the implant’s processor. This device, the size of a deck of cards, includes a microphone, and connects to an instrument called a stimulator that’s placed under the skin behind the ear.
At first, as his doctor had warned, the device was useless. “Everything sounded like Donald Duck,” recalls Simon. But, following instructions, he kept using it.
“One day,” he remembers, “I hooked it up, went down to the kitchen, and my wife said, ‘Good morning.'” I couldn’t believe it! ‘I heard you,’ I told her, ‘I understand you!’ And then I ran around turning on the water, ringing the doorbell, anything you can imagine!”
Today, Simon can hear reasonably well on the phone; better yet in one-on-one situations; can appreciate music, within limits; and can again socialize with friends. “I’ve got my life back, ” he asserts.
INVOLVED IN CONTROVERSY
Simon is one of about 500,000 Americans who are profoundly hearing impaired. It’s a tough condition, says Donald Eddington, an expert on cochlear implants with MIT’s Research Laboratory of Electronics who works with Simon’s physician, Joseph Nadol, at the Massachusetts Eye and Ear Infirmary (MEEI). “Communicating is so hard that only the absolute essentials are dealt with,” he notes.
Eddington got into the field in the late ‘70s after graduating from the University of Utah with an electrical engineering degree. “I was getting married,” he notes, “so I got job in a lab that was studying how electrical stimuli affect the visual system.” When he later took aim at a Ph.D., he began focusing on a related problem: using electrical stimulation to boost hearing in the profoundly deaf.
It was a field then rife with controversy, most of it focused on cochlear implants — instruments whose business end is a bundle of electrodes that doctors surgically place into the cochlea.
The cochlea is a spiral-shaped organ that’s smaller than the nail on a little finger. Despite its size, it’s what lets us turn sound waves into electrical signals. The key to this capability is the cochlea’s hair cells. These cells are invisible to the naked eye, and their hairs are one one-hundredth the diameter of those on our heads. But their subtle movements in response to sounds are what let us converse, enjoy music, and instantaneously locate where a blaring horn’s clangor is coming from.
The problem for cochlear-implant experts is that there are 15,000 hair cells, which are linked to twice that many auditory nerve fibers. Early implants, with just one electrode, presumably triggered just a tiny share of the user’s auditory nerves. “They presented a very impoverished picture to the brain,” says Eddington.
The luckiest users scored about 5 percent in identifying a list of common words like “lot” and “home.” Their lip–reading improved. And, they could do some basic communicating by phone. “If someone asked their spouse about the idea of going out to dinner,” Eddington explains, “they might be able to tell the difference between ‘yes’ and ‘no.'”
The gains were so modest, and so chancy, that many potential candidates ruled out using implants. But Eddington — who heads a cochlear implant laboratory that’s run collaboratively by MIT, Harvard and MEEI — says their performance has improved dramatically since. Typical users today score 40 percent on word tests, and hold fluent conversations in quiet circumstances by combining lip-reading with the sound from the implants. About a third of users, meanwhile, can make good use of the telephone.
What led to such improvements? One key, pioneered by Eddington and others, was to move to six-electrode implants. Others reflect advances in sound-processing techniques: for example, avoiding interference between electrodes.
The cochlea is filled with a conductive fluid, notes Eddington, so when one electrode fires, “Current spreads along the cochlea, and there’s interaction between electrodes.” The solution was to phase the activation of the electrodes. With tiny gaps between each firing, hearing improves markedly.
What’s ahead? Eddington is working on a system with two 16-electrode arrays — one for each ear. “We have good evidence that the brain can integrate information from two implants,” he notes. Such a device might solve what’s sometimes called the cocktail-party problem. “A sound that is coming from your side will be stronger in the ear on that side,” he notes, “and will also get to that ear before the other one. Being able to localize sound sources is the one thing that helps us in conversations at parties.”
Other groups are looking for gains elsewhere — for example, by creating better links between electrodes and the auditory nerves. Eddington believes that one way or another, major new strides are coming. “This is a field that’s accelerating,” he says. “Given the progress we’ve seen already, I think there’s great promise for new developments over the next 10 to 15 years.”