New brain-machine interfaces that exploit the plasticity of the brain may allow people to control prosthetic devices in a natural way.
Imagine a piece of technology that would let you control an apparatus simply by thinking about it. Lots of people, it turns out, have dreamed of just such a system, which for decades has fired the imaginations of scientists, engineers, and science fiction authors. It’s easy to see why: By transforming thought into action, a brain-machine interface (BMI) could let paralyzed people control devices such as wheelchairs, prosthetic limbs, or computers. Further out in the future, in the realm of sci-fi writers, it’s possible to envision truly remarkable things, like brain implants that would allow people to augment their sensory, motor, and cognitive abilities.
But despite all the advances, we are still a long way from a really dependable, sophisticated, and long-lasting BMI that could radically improve the lives of the physically disabled, let alone one that could let you see the infrared spectrum or download Wikipedia entries directly into your cerebral cortex. Researchers all over the world are still struggling to solve the most basic and critical problems, which include keeping the implants working reliably inside the brain and making them capable of controlling complex robotic prostheses that are useful for daily activities. At the risk of losing its credibility, the field now needs to transform BMI systems from one-of-a-kind prototypes into clinically proven technology, like pacemakers and cochlear implants.
In the cover article of IEEE Spectrum’s March issue, Jose Carmena, an associate professor of electrical engineering, cognitive science, and neuroscience at the University of California, Berkeley, writes that it’s time for a new approach to BMI design. His team has zeroed in on one crucial piece of the puzzle that they feel is missing in today’s standard approach: how to make the brain adapt to a prosthetic device, assimilating it as if it were a natural part of the body. Most current research focuses on implants that tap into specific neural circuits, known as cortical motor maps. With such a system, if you want to control a prosthetic arm, you try to tap the cortical map associated with the human arm. But is that really necessary?
The group’s research has suggested–counterintuitive though it may seem–that to operate a robotic arm you may not need to use the cortical map that controls a person’s arm. Why not? Because a person’s brain is apparently capable of developing a dedicated neural circuit, called a motor memory, for controlling a virtual device or robotic arm in a manner similar to the way it creates such memories for countless other movements and activities in life. Carmena’s experiments demonstrated that learning to control a disembodied device is, for a person’s brain, not much different from learning to ski or to swing a tennis racket. It’s this extraordinary plasticity of the brain, they believe, that researchers should exploit to usher in a new wave of BMI discoveries that will finally deliver on the promises of this technology.