Last year, Erik Sorto (above) did something he hadn’t been able to do in more than a decade: he lifted a glass to his lips and took a sip. The feat represented an incredible advance not only for Sorto but also for neuroscience. Sorto is paralyzed from the neck down; with the help of a robotic arm and brain implants that assist him in turning his intentions into actual motions, he is now able to sip beverages, offer handshakes, and even play “rock, paper, scissors.”
“I was surprised at how easy it was,” says Sorto about the first time he was able to control a robotic limb. Sorto’s sipping success came as a participant in a clinical trial led by principal investigator Richard Andersen, Caltech’s James G. Boswell Professor of Neuroscience, who has developed implantable neuroprosthetics that create natural and fluid motions by using a person’s intent to move. The results of the trial were published in the May 22 edition of the journal Science.
“When you move your arm, you really don’t think about which muscles to activate and the details of the movement. Instead, you think about the goal of the movement. For example, ‘I want to pick up that cup of water,’” Andersen says. “So in this trial, we were successfully able to decode these actual intents, by asking the subject to simply imagine the movement as a whole, rather than breaking it down into myriad components.”
Andersen and his colleagues were able to improve upon current neuroprosthetics by implanting them in a different brain region—the posterior parietal cortex (PPC). Most current implants target the motor cortex instead. In the clinical trial—designed to test the safety and effectiveness of this new approach—Andersen’s Caltech team collaborated with surgeons at Keck Medicine of USC and the rehabilitation team at Rancho Los Amigos National Rehabilitation Center. The surgeons implanted a pair of small electrode arrays in two parts of Sorto’s PPC. The arrays were connected by cable to a system of computers that processed the signals, decoded what it was Sorto intended to do, and then sent those signals to output devices that included a robotic arm developed by collaborators at Johns Hopkins University.
Once he’d recovered from the surgery, Sorto began learning how to use his thoughts and intentions to control first a computer cursor and then the robotic arm. “This study has been very meaningful to me,” says Sorto. “It gives me great pleasure to be part of the solution for improving paralyzed patients’ lives.” —JSC