COLUMN ONE : Rewiring the Mind and Body : Bionic devices are moving from the pages of science fiction into the lives of the deaf, blind and paralyzed. Today’s technology is crude, but the future is promising.
In the research logs of the House Ear Institute in Los Angeles, Pat Diener is Patient No. 18. She is 26 years old, and she is going deaf--and what has landed her in the annals of science are the microscopic electrodes that doctors have buried deep inside her brain.
Two fine platinum wires--as thin as a human hair and covered with Teflon--run underneath the woman’s skull, connecting the electrical circuitry inside her head to a black plastic plug that sticks out from behind her left ear. From there, Diener can wire herself into a pocket-size “speech processor†that picks up sound and transmits it to the electrodes, enabling the brain to interpret it.
If it sounds futuristic, it is. In Patient No. 18, doctors have created a bionic woman.
She is not, of course, the kind of fast-running, high-jumping, superhuman character that Hollywood delivered to television viewers in the 1970s. Indeed, the implant that rests inside the dense bundle of nerves that compose Diener’s brain stem cannot match what nature can provide, let alone exceed it.
Yet the same space-age technology that enables the soft-spoken Indio resident to identify certain simple sounds--a telephone ringing, a dog’s frantic bark, the blaring horn of an oncoming car--may someday help the blind to see and the paralyzed to walk. And over the very long term, researchers say, this work may come closer to television’s science fiction fantasy than the screenwriters of two decades ago might have imagined.
This is the realm of bionics, or “neural prosthetics,†implantable devices that use electricity to stimulate nerves and muscles that cannot work on their own. It is a world where modern electronics meets the oldest and most sophisticated engineering achievement of all time: the human body.
The point man in this high-tech endeavor is Dr. Terry Hambrecht, director of the National Institutes of Health’s neural prosthesis program, a 23-year effort to develop electronics for the body, funded by the federal government at $7 million annually.
A surgeon who also has a degree in electrical engineering, Hambrecht says his immediate goal is to help the disabled. But he also sees himself as a bricklayer of sorts, building a foundation for the time when electrodes may be implanted into people’s brains to enable humans to control machines with their minds.
Imagine, he says, the things you might be able to do by just thinking about them: being able to type without ever touching a keyboard or driving a car without putting your foot on the gas pedal.
“As we go into the 21st Century,†Hambrecht said, “we certainly will be able to tap into different parts of the brain, in terms of putting information in. In my lifetime, we will not go well beyond restoring (bodily functions). That is for future generations, but it is going to happen. There are going to be interfaces that will allow us to become ‘superhuman.’ â€
The research is already traveling down that road. At Emory University in Atlanta, neurophysiologist Donald Humphrey is developing electronic devices that he hopes will enable a monkey to move a robotic arm just by thinking about it.
Within the next few months, Humphrey and his team will implant electrodes into the area of the monkey’s brain responsible for motor control in an attempt to determine if the animal’s brain signals can be harnessed and transmitted via computer and sound waves to the robot.
He says he is confident of success. And someday--Humphrey will not predict when--he hopes that the technology he develops might be used to give amputees computerized artificial limbs that would work nearly as well as real ones.
“They had the program (on) the bionic man many years ago,†Humphrey said, “and they didn’t know what they were talking about, but this is quite along those lines. Suppose one could make an artificial limb that would work as well and look as good as the one the bionic man had. If those devices could be developed, then these brain signals could be used to control those artificial limbs.â€
It is a startling thought to other researchers as well.
“When I first read about this I couldn’t believe that they (the NIH) had actually issued this contract,†said William Agnew, who supervises research in neural prosthetics at the Huntington Medical Research Institutes in Pasadena. “It’s so far out. But the technology is here, and it’s just a matter of getting the software and hardware together to carry it out. That alone is pretty mind-boggling.â€
For now, most scientists working in this field--there are an estimated 500 worldwide--are setting their sights a little lower. They are concentrating on developing safe and effective electrodes that will be used, and in some cases are being used, to grant a very small measure of independence to people with a host of different disabilities, people such as Diener.
Diener suffers from a rare and devastating hereditary disease in which tumors destroy the nerves that control her hearing. She has lost hearing in her left ear, and although she has some hearing in the right ear, Diener has been told by doctors to prepare for when the tumors will rob her of that as well.
When that day comes, Diener knows, she will not be able to hear without the aid of the experimental “auditory brain stem implant†that doctors inserted in her brain two years ago when they took out the tumors in her left ear.
“When they first told me about this, I pretty much jumped on board and said: ‘OK, let’s do it,’ †she said. “The prospect of being deaf really bothered me, and it didn’t bother me to have this device in my head.â€
She pulls back her straight, light brown hair to reveal the plug that protrudes about an inch from behind her ear. “A few people (who suffer from the same disease) have called me and said they just don’t like the idea of having something sticking out of their head, but I can tell you, once you get it in there you don’t know the difference.â€
The implant is far from perfect. “It sounds,†Diener said bluntly, “like a garbage disposal.†She will never be able to enjoy the strains of Beethoven, but she can hear the doorbell and telephone, and by combining the device with her lip-reading ability she can understand most speech. And that is far better, she said, than nothing at all--a refrain often heard by those who work in this field.
The idea of using electricity to stimulate muscles and nerves that no longer work is not new. Cells of the nervous system communicate with one another by means of electrical signals that occur naturally. The theory of neural prosthetics is that electrical current, passed into the body in short, controlled bursts, can substitute when nature no longer works.
Researchers have dreamed about, and tinkered with, this notion since the days of Benjamin Franklin, although those early experiments--including one in 1874 in which an electrode was inserted into the brain of a woman whose skull had been eaten away by a tumor--could hardly be considered safe. The work has often been frustrating; as recently as 20 years ago, scientists in Utah and Britain tried to create artificial vision through electrodes placed on the surface of the brain, but they concluded that it could not be done.
Yet over the past decade--spurred by continuing advances in microchip technology--the field of neural prosthetics has taken several important leaps forward, including recent advances toward the dream of artificial vision.
Bionic devices that enable victims of spinal cord injuries to void their bladders are commercially available in Europe, and a small number of devices that assist people with respiratory disorders are available in the United States. Still in the experimental stages, and close to being approved, are devices to control epileptic seizures. Further down the line are implants that would help restore sexual function to paralyzed people.
And in what is clearly the field’s biggest mass market success, 7,000 people who were totally deaf now have “cochlear implants,†which restore hearing--albeit crude--through electrodes inserted into the cochlea of the inner ear.
The implants are expensive--about $15,000 apiece plus another $15,000 or so for the surgery to implant them. They are also controversial within the deaf community, where some complain that giving children the implants will destroy close-knit family bonds that are developed through the use of sign language.
The cochlear implant, which has been available since 1985, is by far the most sophisticated electronic device ever implanted in humans. Its development has laid the crucial foundation for more elusive applications, such as restoring sight to the blind and enabling the paralyzed to walk. Michael Merzenich, a UC-San Francisco professor who is an expert in cochlear implants, calls them “a harbinger of things to come.â€
Just last month, in what experts hailed as a promising development in the quest for artificial vision, Hambrecht and a team of NIH surgeons reported that they had implanted electrodes into the visual cortex--the area of the brain responsible for sight--of a 42-year-old blind woman, enabling her to see distinct dots of light.
The delicate surgery, which lasted 12 hours, marked the first time that doctors have implanted permanent electrodes into that part of the brain. The woman, who has been blind for 22 years as a result of glaucoma, received 38 tiny electrodes, each about one-third the thickness of a human hair.
During four months of experiments, the NIH researchers stimulated the electrodes with low levels of electricity--about 1 millionth the current necessary to illuminate a light bulb. They found that each electrode, when stimulated, would repeatedly produce the same image in the same place--for example, a red dot the size of a nickel on the left, a blue dot the size of a pinhead straight ahead.
The most significant result was that the woman was able to see simple patterns of light, including the letter I, when selected electrodes were stimulated. The next step is to implant a more complex system, consisting of 250 electrodes, in the hope that it will produce more complex patterns.
Elsewhere, at the University of Utah, researchers are attempting to develop an artificial eye with a system that would consist of a miniaturized video camera mounted on a pair of eyeglasses and connected to electrodes implanted in the visual cortex. But according to the lead researcher, Richard Normann, the project will not be completed until at least the turn of the century.
In every conversation there is a note of caution.
“We don’t anticipate that they are going to be able to go to an art gallery and appreciate a fine master,†Hambrecht said. “But on the other hand, we think we can give them rudimentary vision that will allow them to read and help them in their mobility.â€
The research is as painstaking as it is complex. The body was never meant to house computer chips and cables--it has taken scientists decades just to figure out what materials do not cause harm to tissues and nerves, and how much electricity is too much.
Teflon, they have learned, works well for insulating wires, as does silicone rubber. The synthetic material Dacron is a perfect backing for electrodes; its open mesh weave helps keep the tiny probes in place inside the body. Silver is toxic to the nervous system, as is copper. Platinum and iridium are safe.
Building these intricate electronic miniatures, which are put together by hand, can take weeks, months or even years. Hambrecht’s next artificial vision experiment will not get off the ground for another two years. It will take that long, he said, for technicians to put together the array of 250 electrodes.
As vexing as this work is, artificial vision may not be bionics’ final frontier. Even more difficult, researchers say, will be restoring arm and leg movement to people who are paralyzed.
“The more you look at the body and the complexity of it, the more you realize how wonderfully the body is put together,†Agnew said. “To try to reproduce standing in a paraplegic, or walking, and to understand all the sensors that are in the knees and the feedback in the brain that is required to achieve balance . . . is very complex.â€
Much of this work is being conducted at Case Western Reserve University in Cleveland, where P. Hunter Peckham, a professor of biomedical engineering, is working on an implantable device that gives quadriplegics enough hand motion to allow them to eat, and other researchers are trying to develop a system that would enable paraplegics to stand or walk.
Jim Jatich is a beneficiary of Peckham’s work. The 43-year-old Akron, Ohio, resident has been paralyzed from the chest down since a diving accident 15 years ago. He is one of six patients who have Peckham’s experimental hand-grasp device.
It is a sophisticated piece of machinery and yet unsophisticated at the same time. When Jatitch moves his right shoulder, he activates a sensor in the center of his chest, which sends signals to a small computer attached to the back of his wheelchair, which relays the information to eight electrodes that are implanted in his left forearm and hand.
In this way, Jatitch can open and close his fingers enough to feed himself and brush his teeth and answer the phone--tasks that he would otherwise be forced to rely on his parents to do for him. On Election Day, he used his hand to vote.
“You see all these new technologies that you read about being put to practical use, and you know that the future is coming closer and closer,†he said. “They’re a long way away from getting you to move your fingers individually, say, to play the piano. But this technology is out there. It’s changed my whole life.â€
The Bionic Body
Research into “neural prostheticsâ€--implantable devices that use electricity to stimulate nerves and muscles that no longer work--in proceeding on several fronts.
How One Device Works:
A neural prosthetic that restores hand movement is being developed at Case Western Reserve University. Six patients have this experimental device, which gives them rudimentary hand movement--enough to feed themselves or hold a toothbrush. It works like this:
To open or close hand, wearer moves shoulder, which forces joystick (A) to press on sensor (B) attached to chest.
Sensor sends signals to microcomputer and transmitter (C), housed in box outside body.
Computer and transmitter send radio signals to pair of antennas--a transmitting antenna worn on body (D) and receiving antenna that is part of electronic receiver implanted under skin (E).
Implant picks up signal and sends electrical impulses along wires under skin to forearm, where they connect to eight electrodes (F).
Current from electrodes stimulates nerves, which generate signals to muscles. Muscles contract, enabling patient to move hand.
A) Joystick rod
B) Sensor (external)
C) Microcomputer and transmitter box (worn outside body)
D) Transmitting antenna
E) Implanted electronic receiver (under skin)
F) Wires and electrodes
*
Uses for the Future:
1) Vision: Experimental. Approval not expected for decades.
2) Hearing (brain stem implants): Experimental. Approval possible within decade.
3) Hearing (cochlear implants): Approved. An estimated 7,000 in use.
4) Epileptic seizures: Experimental. Approval likely within decade, although questions remain about whether devices will work.
5) Respiratory pacemakers: Approved. Small number in use.
6) Hand movement: Experimental. Approval likely within decade.
7) Sexual function: Experimental. Approval not expected for at least 10 years.
8) Bladder evacuation: Experimental in U.S. Approved in Europe; U.S. approval likely within next decade.
9) Standing: Experimental. Approval possible within decade.
10) Walking: Experimental. Approval not expected for decades.
Source: National Institutes of Health; P. Hunter Peckham, professor of biomedical engineering at Case Western Reserve University.
