I'm an MIT professor, but I do not design buildings or computer systems. Rather, I build body parts, bionic legs that augment human walking and running.
In 1982, I was in a mountain-climbing accident, and both of my legs had to be amputated due to tissue damage from frostbite. Here, you can see my legs: 24 sensors, six microprocessors and muscle-tendon-like actuators. I'm basically a bunch of nuts and bolts from the knee down. But with this advanced bionic technology, I can skip, dance and run.
I'm a bionic man, but I'm not yet a cyborg. When I think about moving my legs, neural signals from my central nervous system pass through my nerves and activate muscles within my residual limbs. Artificial electrodes sense these signals, and small computers in the bionic limb decode my nerve pulses into my intended movement patterns. Stated simply, when I think about moving, that command is communicated to the synthetic part of my body. However, those computers can't input information into my nervous system. When I touch and move my synthetic limbs, I do not experience normal touch and movement sensations. If I were a cyborg and could feel my legs via small computers inputting information into my nervous system, it would fundamentally change, I believe, my relationship to my synthetic body. Today, I can't feel my legs, and because of that, my legs are separate tools from my mind and my body. They're not part of me. I believe that if I were a cyborg and could feel my legs, they would become part of me, part of self.
At MIT, we're thinking about NeuroEmbodied Design. In this design process, the designer designs human flesh and bone, the biological body itself, along with synthetics to enhance the bidirectional communication between the nervous system and the built world. NeuroEmbodied Design is a methodology to create cyborg function. In this design process, designers contemplate a future in which technology no longer compromises separate, lifeless tools from our minds and our bodies, a future in which technology has been carefully integrated within our nature, a world in which what is biological and what is not, what is human and what is not, what is nature and what is not will be forever blurred. That future will provide humanity new bodies. NeuroEmbodied Design will extend our nervous systems into the synthetic world, and the synthetic world into us, fundamentally changing who we are. By designing the biological body to better communicate with the built design world, humanity will end disability in this 21st century and establish the scientific and technological basis for human augmentation, extending human capability beyond innate, physiological levels, cognitively, emotionally and physically.
There are many ways in which to build new bodies across scale, from the biomolecular to the scale of tissues and organs. Today, I want to talk about one area of NeuroEmbodied Design, in which the body's tissues are manipulated and sculpted using surgical and regenerative processes. The current amputation paradigm hasn't changed fundamentally since the US Civil War and has grown obsolete in light of dramatic advancements in actuators, control systems and neural interfacing technologies. A major deficiency is the lack of dynamic muscle interactions for control and proprioception.
What is proprioception? When you flex your ankle, muscles in the front of your leg contract, simultaneously stretching muscles in the back of your leg. The opposite happens when you extend your ankle. Here, muscles in the back of your leg contract, stretching muscles in the front. When these muscles flex and extend, biological sensors within the muscle tendons send information through nerves to the brain. This is how we're able to feel where our feet are without seeing them with our eyes.
The current amputation paradigm breaks these dynamic muscle relationships, and in so doing eliminates normal proprioceptive sensations. Consequently, a standard artificial limb cannot feed back information into the nervous system about where the prosthesis is in space. The patient therefore cannot sense and feel the positions and movements of the prosthetic joint without seeing it with their eyes. My legs were amputated using this Civil War-era methodology. I can feel my feet, I can feel them right now as a phantom awareness. But when I try to move them, I cannot. It feels like they're stuck inside rigid ski boots.
To solve these problems, at MIT, we invented the agonist-antagonist myoneural interface, or AMI, for short. The AMI is a method to connect nerves within the residuum to an external, bionic prosthesis. How is the AMI designed, and how does it work? The AMI comprises two muscles that are surgically connected, an agonist linked to an antagonist. When the agonist contracts upon electrical activation, it stretches the antagonist. This muscle dynamic interaction causes biological sensors within the muscle tendon to send information through the nerve to the central nervous system, relating information on the muscle tendon's length, speed and force. This is how muscle tendon proprioception works, and it's the primary way we, as humans, can feel and sense the positions, movements and forces on our limbs.
When a limb is amputated, the surgeon connects these opposing muscles within the residuum to create an AMI. Now, multiple AMI constructs can be created for the control and sensation of multiple prosthetic joints. Artificial electrodes are then placed on each AMI muscle, and small computers within the bionic limb decode those signals to control powerful motors on the bionic limb. When the bionic limb moves, the AMI muscles move back and forth, sending signals through the nerve to the brain, enabling a person wearing the prosthesis to experience natural sensations of positions and movements of the prosthesis.
Can these tissue-design principles be used in an actual human being? A few years ago, my good friend Jim Ewing — of 34 years — reached out to me for help. Jim was in an a terrible climbing accident. He fell 50 feet in the Cayman Islands when his rope failed to catch him hitting the ground's surface. He suffered many, many injuries: punctured lungs and many broken bones. After his accident, he dreamed of returning to his chosen sport of mountain climbing, but how might this be possible?
The answer was Team Cyborg, a team of surgeons, scientists and engineers assembled at MIT to rebuild Jim back to his former climbing prowess. Team member Dr. Matthew Carty amputated Jim's badly damaged leg at Brigham and Women's Hospital in Boston, using the AMI surgical procedure. Tendon pulleys were created and attached to Jim's tibia bone to reconnect the opposing muscles. The AMI procedure reestablished the neural link between Jim's ankle-foot muscles and his brain. When Jim moves his phantom limb, the reconnected muscles move in dynamic pairs, causing signals of proprioception to pass through nerves to the brain, so Jim experiences normal sensations with ankle-foot positions and movements, even when blindfolded.
Here's Jim at the MIT laboratory after his surgeries. We electrically linked Jim's AMI muscles, via the electrodes, to a bionic limb, and Jim quickly learned how to move the bionic limb in four distinct ankle-foot movement directions. We were excited by these results, but then Jim stood up, and what occurred was truly remarkable. All the natural biomechanics mediated by the central nervous system emerged via the synthetic limb as an involuntary, reflexive action. All the intricacies of foot placement during stair ascent —
emerged before our eyes. Here's Jim descending steps, reaching with his bionic toe to the next stair tread, automatically exhibiting natural motions without him even trying to move his limb. Because Jim's central nervous system is receiving the proprioceptive signals, it knows exactly how to control the synthetic limb in a natural way.
Now, Jim moves and behaves as if the synthetic limb is part of him. For example, one day in the lab, he accidentally stepped on a roll of electrical tape. Now, what do you do when something's stuck to your shoe? You don't reach down like this; it's way too awkward. Instead, you shake it off, and that's exactly what Jim did after being neurally connected to the limb for just a few hours. What was most interesting to me is what Jim was telling us he was experiencing. He said, "The robot became part of me."
Jim Ewing: The morning after the first time I was attached to the robot, my daughter came downstairs and asked me how it felt to be a cyborg, and my answer was that I didn't feel like a cyborg. I felt like I had my leg, and it wasn't that I was attached to the robot so much as the robot was attached to me, and the robot became part of me. It became my leg pretty quickly.
Hugh Herr: Thank you.
By connecting Jim's nervous system bidirectionally to his synthetic limb, neurological embodiment was achieved. I hypothesized that because Jim can think and move his synthetic limb, and because he can feel those movements within his nervous system, the prosthesis is no longer a separate tool, but an integral part of Jim, an integral part of his body. Because of this neurological embodiment, Jim doesn't feel like a cyborg. He feels like he just has his leg back, that he has his body back.
Now I'm often asked when I'm going to be neurally linked to my synthetic limbs bidirectionally, when I'm going to become a cyborg. The truth is, I'm hesitant to become a cyborg. Before my legs were amputated, I was a terrible student. I got D's and often F's in school. Then, after my limbs were amputated, I suddenly became an MIT professor.
Now I'm worried that once I'm neurally connected to my limbs once again, my brain will remap back to its not-so-bright self.
But you know what, that's OK, because at MIT, I already have tenure.
I believe the reach of NeuroEmbodied Design will extend far beyond limb replacement and will carry humanity into realms that fundamentally redefine human potential. In this 21st century, designers will extend the nervous system into powerfully strong exoskeletons that humans can control and feel with their minds. Muscles within the body can be reconfigured for the control of powerful motors, and to feel and sense exoskeletal movements, augmenting humans' strength, jumping height and running speed. In this 21st century, I believe humans will become superheroes. Humans may also extend their bodies into non-anthropomorphic structures, such as wings, controlling and feeling each wing movement within the nervous system. Leonardo da Vinci said, "When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you will always long to return." During the twilight years of this century, I believe humans will be unrecognizable in morphology and dynamics from what we are today. Humanity will take flight and soar. Jim Ewing fell to earth and was badly broken, but his eyes turned skyward, where he always longed to return. After his accident, he not only dreamed to walk again, but also to return to his chosen sport of mountain climbing. At MIT, Team Cyborg built Jim a specialized limb for the vertical world, a brain-controlled leg with full position and movement sensations. Using this technology, Jim returned to the Cayman Islands, the site of his accident, rebuilt as a cyborg to climb skyward once again.
Ladies and gentlemen, Jim Ewing, the first cyborg rock climber.