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Paralyzed Patients Control Robotic Arm With Their Minds
16 May 2012 2:10 pm
A thought-powered robotic arm could put independence within reach for disabled patients, researchers report. In a new study, two people with almost-complete body paralysis were able to reach and grasp small foam balls and a thermos of coffee with a robotic arm using only their brain signals to direct the motion. The result, a first for human subjects, brings scientists a step closer to restoring mobility for people with spinal cord injuries, lost limbs, and other conditions that limit movement.
Mind-melding between animals and machines isn't new; researchers have been attempting it since the 1970s. Past studies in brain-machine interfaces have enabled monkeys to control robotic arms and paralyzed people to control cursors on a screen. But researchers didn't know if humans could control robotic arms to perform finer, more complex tasks, such as maneuvering in three dimensions and grasping a small object without moving it or knocking it over.
John Donoghue, a neuroscientist at Brown University who led the cursor-controlling experiment, and colleagues tested the idea on two patients with "locked-in" syndrome. "S3," a 58-year-old woman, suffered a brainstem stroke 15 years ago that left her without the ability to move any of her limbs or speak. "T2," a 66-year-old man who survived a brainstem stroke in 2006, can move only his eyes and head.
Each patient had an array of electrodes about the size of a baby aspirin implanted in his or her motor cortex, the part of the brain that controls voluntary movements. The array, called BrainGate, reads a pattern of brain signals and then sends them via wires to an external computer that translates it into a command. A certain pattern of activity might tell a robotic arm to move right or left; another might raise or lower it. Calibrating the device to patients' brain activity took about half an hour; they weren't trained to use the implant.
Using only their thoughts to control the robotic arm, S3 and T2 were able to reach out and touch a series of 6-centimeter foam ball targets 49% to 95% of the time in over 200 trials. Two-thirds of the reaches resulted in successful grasping. S3 was also able to lift a bottle from a table, bring it to her lips, and sip coffee from it through a straw.
"This was the first time in 15 years that she was able to drink on her own," says study co-author Leigh Hochberg, a neurologist at Massachusetts General Hospital in Boston. "And the smile on her face was something my colleagues and I won't forget." The results, reported online today in Nature, suggest the technology could help patients with brain or spinal injuries recover some of the movement everyday activities require. The study also quells concerns that the implants lose their signal-reading capabilities over time. The researchers acknowledge some deterioration in S3's array, which was implanted more than 5 years ago—but it is still fully capable of recording her brain activity for control of the robotic arm.
"This is quite a step forward," says Andrew Jackson, a neuroscientist at Newcastle University in the United Kingdom who was not involved in the study. "It's also a good demonstration of why basic science matters—because it can lead to applications that can significantly improve patients' quality of life."