This month, A Beautiful Perspective is exploring touch in all its forms and contexts. Click here to read more stories from the TOUCH Issue.
Fifteen years ago, Magnus Niska stood in his kitchen in Northern Sweden and crushed eggs as he tested out his new bionic hand. It was a mess. Yolk and shell oozed through the metal fingers of his alien limb while he opened and closed its five appendages, struggling to calibrate how much pressure he should use to securely grasp an egg without breaking it. If that sounds easy enough, it wasn’t. One by one, Niska used his natural left hand to take an egg out of the carton and place it into his artificial right hand. Then, with frustrating force, he’d squeeze the egg and it would crack and shatter. From a carton of 10, he crushed at least seven before getting the pressure right.
Niska now wears a new prosthesis—one with sensors in the thumb that allow him to feel. Not long ago, that would’ve been an impossible feat. Now, electrodes hardwired into his nervous system pick up signals from the fingertip, and carry that data straight to Niska’s brain as electrical impulses. Not only can he safely hold an egg, he can also grip his cellphone, shake someone’s hand, and pile a plate full of food at a buffet without worrying about it toppling over.
“It’s the small things in life,” he says.
Niska, who lost his forearm due to a tumor in 2003, is the first recipient of one of the most advanced bionic limbs ever invented. However, his case is the exception, not the norm.
Most prosthetic limbs today remain expensive, primitive, uncomfortable and functionally unreliable. But researchers around the globe are working to fix that. They’re designing devices that restore natural functionality, developing treatments that overcome the debilitating side effects of amputation surgery, and enabling people to recover the tactile sensations that help keep them in touch with the world.
For such small appendages, hands take up a lot of real estate in the brain. Take, for example, the 3D-sensory “cortical homunculus,” a Gollum-like model designed by psychologists, which depicts a distorted human form with body parts extenuated in proportion to the amount of space they take up for sensory processes in the brain. Its lips are engorged and a dog-like tongue hangs from the mouth, but it’s the oversized hands that demand the most attention. Which makes sense. Consider how easy it is to feel your way through a dark room or differentiate between things in your bag without having to look. Now imagine losing that sense all together.
After an operation, amputees don’t just suffer from the lack of a limb—they’re often haunted by the lost appendage. Up to 80 percent of amputees experience phantom limb syndrome, a disorienting and painful condition, which Max Ortiz Catalan, an engineer at Chalmers University of Technology in Gothenburg, Sweden, thinks may be caused by neurons trying to adjust to the sudden lack of function. All that neural circuitry once dedicated to a hand or foot gets tangled up and misfires, but by replacing missing limbs with sensory prostheses, Ortiz Catalan says amputees can effectively fill the void and overcome that condition.
“We’re trying to use all those neural networks again for something purposeful,” says Ortiz Catalan, who built Niska’s bionic arm. “Rather than … randomly firing and entangling with pain, we give those neural circuits back a job that was lost when the limb was lost.”
Most bionic hands use sensors placed on the skin to pick up signals from the muscles underneath. Flexing the forearm one way may elicit the bionic hand to open. Flexing it the other way would cause it to close. But skin is thick and can make it tough to pick up a strong signal, so this method can be unreliable.
Ortiz Catalan and his colleagues instead place the electrodes inside the body, connecting them to nerves and muscles. They surgically fix a titanium mount into the patient’s bone, then fasten the prosthesis to a rod that pokes out of the stump. Electrodes attached to the patient’s nervous system allow for seamless control over the bionic limb, and, for Magnus Niska, enable him to feel his surroundings.
Niska’s bionic arm might sound like a device ripped from the pages of Neuromancer, but it’s hardly the most advanced prosthesis around. Where Ortiz Catalan places electrodes inside the body to bypass the skin, other engineers want to take the signal even closer to the source and plug their prostheses directly into the body’s natural infrastructure.
At Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland, biomedical engineer Silvestro Micera uses a technique that implants the electrodes into nerves themselves. In 2014, he and his team restored real-time sensory feeling into an amputee’s bionic hand in the lab for the first time.
“The nerves are kind of a highway, which link the periphery to the brain,” he says. “After amputation, we can use artificial sensors and electrodes implanted around or inside the nerve to kind of mimic the natural situation.”
Where Ortiz Catalan places the electrodes on and around muscles and nerves, Micera implants them into the nerves. To visualize the difference between these two techniques, imagine a room full of people. Now imagine you have to deliver a message to one of those people. In Ortiz Catalan’s approach, you might pipe that message through a speaker—it’s effective but not the most direct method. There’s a lot of excess noise. In Micera’s approach, you enter the room and deliver the message directly to the intended recipient—it’s direct but more demanding.
Both have their advantages and drawbacks. For Micera, the signal is more acute and may allow for more refined sensory perception, but it’s more invasive and may be less durable in the long run (the longest an amputee has worn Micera’s device is for six months). For Ortiz Catalan, the operation may be long lasting (one of his patients has worn the same implant for nearly two decades), but doesn’t allow for as acute communication between the prosthesis and the brain.
Since receiving his sensory prosthesis a year and a half ago, Niska has found himself reclaiming aspects of his past life. “I can use my prosthesis more now,” he says. “I don’t crush things. I can use more of my right hand, and save my left hand. I work 100 percent as a truck driver, and drive [80,000 miles] per year. That’s not possible with other prosthetics.”
But few people have access to such advanced devices. Ortiz Catalan estimates that a commercial product like the one Niska wears would cost $100,000 or more. Micera put that figure in the tens of thousands. Either way, it’s prohibitively expensive and will likely take years to make it to the commercial market.
In the meantime, researchers like EPFL’s Giulio Rognini are developing techniques to assist amputees who suffer from phantom limb syndrome, which can make prostheses feel so disorienting that people abandon them entirely.
To increase what he calls “prosthetic embodiment,” Rognini uses augmented reality, training amputees to sense and visualize their prosthesis as belonging to their body.
“Research shows that your perception of your body is grounded in the way the brain integrates different multi-sensory signals,” he says. “What we’re trying to do is restore this coherent multi-sensory input from this prosthetic device, so that it’s perceived as your own body. What’s crucial is that one sense is not enough to recreate the sensation of a cohesive body. We combine two senses—vision and touch.” In a recent study, patients felt higher prosthetic embodiment for up to 10 minutes after the session.
Ortiz Catalan uses augmented reality and machine learning to match up what a patient sees with what she feels. “It’s non-invasive,” he says. “And you only require a computer. It’s safe, there are no side effects, and it’s easy to distribute.” Patients from Canada to Chile to Australia have already benefited from this technique.
Science fiction predicted a future fitted with humanoid robots, sentient A.I., and lifelike bionic limbs. That future is soon. Thanks to advanced prosthetics and new treatment options, amputees are in ever closer contact with the world around them. They no longer crush eggs, but simply make breakfast.