“We want to galvanize people’s imaginations,” says Miguel Nicolelis, the Brazilian neuroscientist at Duke University who is leading the Walk Again Project’s efforts to create the robotic suit. “With enough political will and investment, we could make wheelchairs obsolete.”
Mind-controlled leg armor may sound more like the movie “Iron Man” than modern medicine. But after decades of testing on rats and monkeys, neuroprosthetics are finally beginning to show promise for people. Devices plugged directly into the brain seem capable of restoring some self-reliance to stroke victims, car crash survivors, injured soldiers and others hampered by incapacitated or missing limbs.
A sip of water
Nicolelis is a pioneer in the field. In the 1990s, he helped build the first mind-controlled arm. Rats learned that they could manipulate the device to get a drink of water simply by thinking about doing so.
In that project, an electronic chip was embedded in the part of each rodent’s brain that controls voluntary muscle movements. Rows of wires that stuck out from the chip like bristles on a brush picked up electrical impulses generated by brain cells and relayed those signals to a computer.
Researchers studied the signals as the rats pushed a lever to guide the arm that gave them water, and they saw groups of neurons firing at different rates as the rats moved the lever in different directions. An algorithm was developed to decipher the patterns, discern the animal’s intention at any given moment and send commands from the brain directly to the arm instead of to the lever. Eventually, rats could move the arm without pushing the lever at all.
Using similar brain-machine interfaces, Nicolelis and his colleagues learned to translate the neural signals in primate brains. In 2000, they reported that an owl monkey connected to the Internet had controlled an arm located 600 miles away. Eight years later, the team described a rhesus monkey that was able to dictate the pace of a robot jogging on a treadmill half a world away in Japan.
Small groups of neurons, it seemed, were surprisingly capable of communicating with digital devices. Individual cells learn to communicate with computer algorithms more effectively over time by changing their firing patterns, as revealed in a study of a mouse’s brain published last year in Nature. “You can count on this plasticity when designing a prosthetic,” says Jose Carmena, a neuroscientist at the University of California at Berkeley. “You can count on the brain to learn.”