Researchers enabled a quadriplegic patient to perform simple tasks with a robotic arm by implanting electrodes into a part of his brain where intentions form.
The experiment, by the California Institute of Technology (Caltech), the University of Southern California (USC) and Rancho Los Amigos National Rehabilitation Center, is the first of its kind, paving the way for further improvements in treatment of severely disabled people.
The patient, 34-year-old Erik Sorto, has been paralysed from neck down since the age of 21 when he was shot in the back. For the first time since the crippling injury, he can now perform simple tasks unassisted, such as drinking a beer or making a handshake gesture.
“I joke around with the guys that I want to be able to drink my own beer, to be able to take a drink at my own pace, when I want to take a sip out of my beer and to not have to ask somebody to give it to me,” Sorto said.
The study published in the latest issue of the Science Journal has provided him with means to reach his humble dream.
The scientist behind the project took a novel approach and unlike earlier attempts that implanted electrodes directly into those parts of the brain responsible for motion, they targeted areas in the posterior parietal cortex (PPC) where neurons exchange information about the intended motoric activity.
"The PPC is earlier in the pathway, so signals there are more related to movement planning - what you actually intend to do - rather than the details of the movement execution," said Richard Andersen, a neuroscience professor at Caltech.
"When you move your arm, you really don't think about which muscles to activate and the details of the movement - such as lift the arm, extend the arm, grasp the cup, close the hand around the cup, and so on. Instead, you think about the goal of the movement, for example, 'I want to pick up that cup of water.'”
In the experiment, which started in 2013 with a demanding five-hour surgery, the researchers proved they were able to decode the patient’s intentions by simply asking him to imagine a movement as a whole rather than breaking it down into individual components.
While the patient was imaging various types of movements, the researchers were monitoring his brain activity using magnetic resonance imaging.
This information was then used to steer a computer cursor or to direct a robotic arm situated next to the patient to the intended location.
The results were satisfying. Sorto was able to move the robotic arm much more smoothly than patients involved in earlier studies.
"I was surprised at how easy it was," said Sorto, a single father of two. "I remember just having this out-of-body experience, and I wanted to just run around and high-five everybody."
The route to this success was quite challenging. The surgery itself was quite demanding as it marked the first instance implants were being placed into this particular part of the brain.
“These arrays are very small so their placement has to be exceptionally precise, and it took a tremendous amount of planning, working with the Caltech team to make sure we got it right," said Charles Y. Liu, professor of neurological surgery at USC.
“Keep in mind that what we're able to do - the ability to record the brain's signals and decode them to eventually move the robotic arm - is critically dependent on the functionality of these arrays, which is determined largely at the time of surgery."
After the operation Sorto started his rehabilitation and training, learning with the help of therapists, how to correctly visualise the movements to make a computer connected to ports extending from his skull, to understand his intentions.
"It was a big surprise that the patient was able to control the limb on day one, the very first day he tried," Andersen said. "This attests to how intuitive the control is when using PPC activity."
The project is now entering its third year and the researchers are hopeful the technology could in the future help many people trapped in a failing body after devastating injuries, strokes or even due to degenerative diseases.
"This study has been very meaningful to me," said Sorto. "As much as the project needed me, I needed the project. It gives me great pleasure to be part of the solution for improving paralyzed patients' lives.”