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Beyond Human

Living with Robots and Cyborgs

Tom Doherty Associates

You, Too, Can Be Superhuman

How close is science to making us stronger, tougher, smarter, just plain better?

Humans are general-purpose animals — perhaps the best.

Our bodies aren't best at any one sense or strategy, but we do a lot of things well. Dogs have better ears and noses; hawks have better eyes; bears, wolverines, and big cats have superior claws; horses and antelopes are faster; and so on. Even our teeth are adapted to an omnivore diet — front teeth for biting fruit and meat, rear molars for grinding nuts and plant fibers.

Rather than tailor ourselves, or wait for evolution to do it, we invent objects to help us overcome these shortcomings. This runs from atlatls, the throwing sticks that helped hunter-gatherers throw spears harder and faster, to binoculars to see the far horizon. When accident or disease results in a disabling physical condition, it's just another shortcoming.

Peg legs, wooden arms with hooks, glass eyes, false teeth, hearing horns, and eyeglasses are traditional examples of what we now call synthetic replacements, or "prostheses," for damaged or missing parts and functions of the human body. Medical prosthetics is a field with a venerable history. George Washington wore false teeth carved of ivory or wood, and Ben Franklin wore spectacles.

The early devices were all clearly false, and temporary.

But as they were improved in the last few decades, they became smaller, more intimate (contact lenses and some hearing aids), more permanent (tooth implants), and harder to detect.

The range of available implants is expanding constantly, blurring the line between technology and biology: stainless-steel hips, knees, and shoulders, random bits of metal (titanium rods in lower leg bones, metal plates on skulls), heart pacemakers, insulin pumps, colostomy bags, drains in ears, heart valves, steel mesh plates to replace bone, implantable teeth and lenses.

With a rapidly expanding senior population in the developed world, the number of cataract operations and lens implantations has skyrocketed. Over two million devices are implanted every year, and by 1988, more than eleven million people in the United States alone had permanent medical implants.

Arm and leg prostheses look increasingly like flesh-and-blood limbs. As far as social interactions go, the more invisible the implant or attachment, the better.

Most people are not comfortable around individuals in wheelchairs, those wearing artificial devices, or blind people with dogs or canes. Old impulses, buried deep in the human psyche, trigger social awkwardness and avoidance around those who are "different"; in this case, people with visible prostheses. At social gatherings, we pretend they're invisible, or we pepper them with questions about their arm or leg or whatever, then move quickly on to others like ourselves. To the wearer, it must seem that the devices are wearing them.

Eyeglasses are the notable exception, being entirely too common to notice, and only children are amazed by sets of false teeth. It wasn't so long ago that people with hearing aids were routinely left out of conversations, but the tiny new electronic models are worn entirely in the ear, and are largely undetectable. Keeping a person with disabilities socially connected is what the new electronic implantables and prostheses are all about.

Today, multiple amputees don't have to while away their lives in wheelchairs in medical institutions. Increasingly, they are entering the work force by telecommuting from their homes, or even holding down jobs away from home. To paraphrase an old John Wayne movie, when you call these people "handicapped," you'd better be smiling.

Getting a Leg Up: Limb Prostheses

Smart Legs

In 1998, Tom Whittaker did what few people have done: successfully reached the top of Mount Everest. And, oh yes, he has only one foot of flesh and bone. Researcher Hugh Herr would like to make it easier for other amputees, like himself, to climb hills and trudge through snow. He is working on a "smart knee" at Massachusetts Institute of Technology's Leg Laboratory.

Today's partial or full leg prostheses are pretty dumb mechanical devices, unable to respond to changing conditions, such as moving from hard flooring to carpet. Natural legs quickly sense the difference in resistance, and muscles adjust walking speed or force. A truly "smart" artificial leg would be able to do the same.

Today's prostheses boast battery-powered knee joints to allow for easy movement, something like power steering. One company even offers a leg with a hydraulic knee controlled by microprocessor. Linked to sensors that continually measure the position of knee and leg, the chip allows the artificial leg to mimic the motion and gait of the rest of the body. This technology helps the wearer change gait speeds, move from a smooth, hard surface to a rug, and climb slopes or stairs.

Advanced artificial limbs feature comfortable, cushioned sockets, molded closely to fit the remaining leg remnant. Most use "smart plastics" in the socket that adapt to and remember the shape of the residual limb they have to fit. This is intended to eliminate pressure points, and the close fit enables the wearer to better control the movement of the leg. Still, to achieve balance and natural walking or running, the brain needs the feedback from the missing muscles and bones.

But soon, wearers of leg prostheses may be able to feel the ground beneath their artificial feet. At least one manufacturer, the Hanger Orthopedic Group, Inc., is developing pressure sensors for leg prostheses. The Sense of Feel Sensory System is an effort to restore that feedback from the ground to amputees.

Pressure sensors in the sole of the artificial foot send tingling signals to the amputee's residual limb. The more pressure exerted on the artificial foot, the greater the sensation in the residual limb. The amputee's brain soon interprets the sensations in the residual limb as being from the foot, not from the stump, a phenomenon known as cerebral projection. It's definitely a step along the way toward really smart prostheses.

Smart Arms

The Motion Control Utah Arm and Hand is a removable "smart" prosthetic available from Motion Control, Inc., in Salt Lake City. It's a far cry from Captain Hook's wood-plus-hook replacement hand. The result of ongoing research funded by the National Institutes of Health, it is a myoelectric prosthesis, a device run by muscles plus electricity.

The unit is made of a sophisticated nylon composite material, strengthened with carbon fiber and fiberglass that is about the same weight as an arm of flesh and bone. It also looks a lot like a "real" arm. Custom-fitted to the remaining upper arm, the device runs on a self-contained battery that replaces muscle power and enables the elbow to move easily.

Electrodes in the socket are close enough to the wearer's upper arm muscles to detect faint electrical impulses in those muscles. Amplified by the electrodes, the signals are then transmitted to the prosthesis and used to guide the mechanical hand.

The Utah Arm's function is not quite so seamless as the fictional one Luke Skywalker receives at the end of The Empire Strikes Back. It also cannot punch through walls, like the Terminator's. Wearers control the hand by consciously flexing and releasing their upper arm muscles, something that takes considerable practice. After a period of training, however, they can again do many two-handed tasks around the house and even in outdoor jobs.

Artificial hands may look fleshlike, but the skin does not feel anything, so there is no feedback. That means the wearer has to keep looking at the hand to see what it is doing. This is very different from the normal situation, because fingers, especially the tips, are densely supplied with nerve endings for touch and temperature, and a large area on the surface of the cerebral cortex is involved with receiving and interpreting the information.

Under development by Hanger Prosthetics and Orthotics are prosthetic hands with microsensors in the fingertips that respond to hot and cold, and pressure sensors. Both types of sensors send signals to electrodes on the wearer's skin where the prosthetic is attached. The pressure sensors produce a "tingle" response on the wearer's skin. More pressure increases the "tingle" response, so the wearer can tell how tightly or loosely an object is being held.

The temperature electrodes grow warm or cool depending on the signal from the fingertip microsensors, restoring to the wearer the ability to sense temperature with their hands.

New Expectations in Amputee Sports: Toward the Bionic Man

You've seen the pictures in the news: guys in wheelchairs playing basketball. Do you remember the woman leading the hike up the canyon — the one with an artificial leg? And the next time you're on the ski slope, look around and notice the fellow with one leg and tiny skis on the end of his poles.

Increasingly, people who have lost arms or legs are picking up all facets of their pre-accident lives using the latest generation of prostheses.

Amputees are pushing the envelope of the possible, in work and recreation. Today they have a range of leg styles to choose from, and some use more than one model, depending on the activity. Golf for a leg amputee seems reasonable, but what about skiing, rock climbing, running, dancing, biking, or sailing?

Almost ignored until recently, interest in amputee athletics has grown tremendously over the last ten years. In the 1970s and 1980s they were the butt of countless jokes, but now the culture seems to get their point: instilling a sense of self-worth among those who have taken a major reversal.

Following the 1996 Paralympic Games held in Atlanta and the 2000 Games in Sydney, a growing number of amputee athletes have started training to compete in athletic events themselves. Some of these people were athletes before their accidents; some were just young and strong and determined not to let one unfortunate accident slow them down.

The Paralympic Games are the world's second largest sporting event, second to the Olympic Games. More than four thousand athletes from approximately 120 countries competed in the two-week-long Sydney event in October 2000. The program included the normal running, jumping, throwing, and swimming events. Participants are world-class athletes, although so far their times and distances are well off the world mark for their sports.

But that could change.

Could a double amputee wearing very smart, high-tech legs with superior recoil someday be faster than nonamputees? Why not design arm prostheses to be more efficient in the water than arms? There are already "racing models" of artificial legs — why not arms to propel swimmers to faster finishes?

Today's paralympic athletes, demanding high-performance artificial arms and legs, are taking the first steps toward the Six Million Dollar Man and bionic woman of tomorrow.

Electronic Nerves

Ever since Puss in Boots' seven-league boots, people have dreamed of being able to run faster than humanly possible. The first modern superhero, Superman, can "leap tall buildings at a single bound," besides being able to fly by no visible mechanical mechanism at all. Okay, it's a metaphor. Taking it semirealistically, though, all this is clearly impossible if we are confined to flesh and blood, but what about using bionic assist?

The bionic man and woman from the old TV series had superspeed, but we never saw the nuts and bolts of how it was accomplished. The zany clay animation film from Nick Park of a few years ago, The Wrong Trousers, postulated a pair of unstoppable robotic trousers.

But seriously, how close are we to superspeed, or even walking robots? Human walking, it turns out, is very difficult for a mechanical device to master. Walking on two legs demands movable joints, a pelvis, precise coordination among major muscle groups in the legs, and the action of stretchy tendons. If any of these components is missing or diminished, people have various problems with mobility, or can't walk at all.

To achieve upright balance, the body has gravity sensors in the inner ear (the cochlea) and mechanoreceptors (stretch receptors) in skeletal muscles. Together they tell the brain which way is up, and which muscles are working, and enable it to program the legs to walk. At a minimum, eight leg muscles are required to stand; another eight are needed to walk. Graceful walking requires the help of even more muscles. Walking is actually a series of short forward falls, catching the body just in time.

The balancing required in upright walking is still difficult for the human brain, even though our ancestors started doing it several millions of years ago. It's easy to lose the ability to balance if the muscles aren't exercised regularly, and falling is one of the most common symptoms of old age or failing health.

David Reinkensmeyer at University of California, Irvine, is developing a robotic harness that helps the nervous system recover arm and leg movement ability in those with neurologic injuries, such as stroke and spinal cord injury. An intricate set of "mechatronic" devices guides them to relearn walking on a treadmill, giving them only enough strength to move. Such "rehabilitators" help us to understand the adaptive control processes that enable motor learning. We seldom think of robots as a carapace around us, but Reinkensmeyer's are. A single walker-helper is like teams of people who (usually rather clumsily) assist the injured. The great talent of a helping harness is that it is both smart and intimate.

Professor Reinkensmeyer's laboratory develops robotic devices for manipulating and measuring movement in humans and rodents. Instead of costly nurse teams, usually four nurses to one patient, these devices give mechanical assistance in retraining arm movement following stroke. They can provide movement training remotely over the Internet. Such help promises to be among the first widespread medical 'bots.

It's extraordinarily difficult to construct a mechanical device that can walk smoothly on two legs. In Japan, the Honda Motor Company spent more than a decade, and millions of dollars, on a robot that can walk as well as climb and descend stairs. But that's all it can do, and other robotics experts wonder if it was worth all the trouble.

Joe Engelberger, one of the founding fathers of robotic devices, feels that wheeled robots are the most practical, given the design problems of walking ones. Many other roboticists agree with him.

Nonetheless, the work at MIT's Leg Lab and elsewhere continues, in part because of the interest in helping amputees and paralyzed victims of spinal cord injuries. Designing mechanical devices that walk naturally helps the scientists understand how a person walks. Then they can help create better prostheses for amputees, as well as sensor and control systems for paraplegics. As well, humans aren't the whole point. Many smaller robots will need to walk across impossibly rough terrain or even, like geckos, up walls. These uses will transcend humans by doing tasks we cannot, justifying legs as a "new" capability.

Replacing Nerves with Neural Prostheses

People with nervous system diseases or injured spinal cords have different challenges than do amputees. They have all their body parts, but cannot move (or often even feel) them because the connection between brain and muscles has been disrupted or destroyed.

The spinal cord is a bundle of nerve fibers running inside the vertebral bones of the back. The signals they carry connect the brain with the rest of the body. Sensations from skin and muscles travel up into the brain (sensory nerve input to the brain), while signals controlling the movement of muscles travel downward (brain output to motor nerves).

In a person with a damaged spinal cord, the brain no longer receives signals from the mechanoreceptors in the muscles, and it can't issue any commands back to the nerves that control the muscles. For people with damaged spinal cords, the extent of their disability depends on how high up the spinal cord was damaged. Generally, any part of the body below a break or a lesion will be affected. Paraplegia results when the damage is in the midback region, below the shoulders. These people can move their arms, but their legs are paralyzed.

People with broken necks are quadriplegics, unable to move either arms or legs. A common accident occurs when a person dives into too-shallow water, hitting a pool bottom or sand bar underwater, breaking his or her neck. Those unfortunate accidents usually leave the person wholly or partially paralyzed from the neck down. The late actor Christopher Reeve was quadriplegic after breaking his neck in a fall from a horse.

For both paraplegics and quadriplegics, a pair of related technologies, functional electrical stimulation (FES) and brain computer interface (BCI), are being developed.

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Excerpted from Beyond Human by Gregory Benford, Elisabeth Malarte. Copyright © 2007 Gregory Benford and Elisabeth Malarte. Excerpted by permission of Tom Doherty Associates.
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