Thought is many things—a jumble of ideas, feelings, and words—but in our daily lives, its primary purpose is to relay neural information to move our bodies through space. For people living with paralysis, that particular purpose is lost. But as a team of neuroscientists, physicians, and engineers working in the multi-institutional research collaboration BrainGate (now known as BrainGate2) has discovered, when these patients think about or imagine moving, their brains still fire in the same way. By relaying this neuroactivity to a computer program designed to interpret it, patients are able to alter and move the world around them with their minds.
Initially, the team focused on overcoming neural disconnects in order to translate thought into movement. In early trials, patients had a tiny sensor about the size of a baby aspirin implanted in their motor cortex, the part of the brain that controls body movement. Instead of neural activity firing muscles as it once did, through communication between the implanted sensor and a computer that decoded neural activity, patients could mentally control a computer cursor to open emails or play a simple video game. As the technology evolved, patients began to control more complex movements, like guiding a prosthetic robotic arm.
By 2012, BrainGate had appeared in Nature demonstrating how Cathy Hutchinson—a tetraplegic patient who had been unable to move her arms or legs for 15 years—mentally steered a robotic arm toward a bottle, lifted it to her lips, and drank some coffee from a straw.
That sort of complex thought control over the physical world was a monumental landmark for the team, though the accomplishment wasn’t without its shortcomings. (The robotic arm is clunky and the sensor must be connected by wire to a computer, making it all still very tethered to the lab). As described by BrainGate2 trial director Leigh R. Hochberg, M.D., PhD, from Brown University and Massachusetts General Hospital, the true dream for the technology is reconnecting a nervous system within the body in order to give someone who has suffered a spinal cord injury renewed control over their own limbs without burdensome wires looping from head to computer to prosthesis.
Dr. Robert Kirsch is chair of Case Western’s biomedical engineering department and executive director of the VA Center for Excellence in Functional Electrical Stimulation. He’s also part of a Cleveland-based consortium on functional electrical stimulation (FES), members of which have developed brain-computer interfaces that send electrical impulses to electrodes implanted in the arm of a patient, in turn stimulating muscles that make it possible to raise a hand or grasp a cup.
While BrainGate2 developed the software to interpret thoughts of movement into action more than a decade ago, researchers in Cleveland are attracting notice for their work restoring movement to paralyzed individuals using FES directly implanted into the body. But they haven’t yet been able to help people with profound paralysis, who have difficulty giving commands to their FES systems.
The ultimate goal in Cleveland is to bridge these two approaches. It will mean both better understanding brain-recording technology and better decoding participants’ intent as they think through moving a virtual arm to brush their teeth, for example. Then it will be a matter of translating these thoughts into the FES system so that patients can again use their arms and hands for simple tasks, just by thinking about them.
“When we ask patients with tetraplegia their number one priority, they tell us they want to rub their nose and eyes,” said Kirsch in a statement. “It’s the simple things they can’t do. They rely on caregivers for everything, and these technologies could restore some independence.”
