If you woke up one morning and found yourself paralyzed, what would you miss? Since the day a gunshot wound rendered him unable to move 13 years ago, quadriplegic Erik Sorto has missed the little things most. “I joke around with the guys that I just want to be able to drink my own beer,” he says. “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.”
Now, thanks to an incredible collaboration between scientists at CalTech, USC’s Keck School of Medicine and Rancho Los Amigos National Rehabilitation Center, the now-34-year-old can drink on his own again. He has become the first person in the world to have a neural prosthetic device implanted into the region of his brain where intentions are formed, allowing him to control a robotic arm with his imagination.
“What we’ve done is shift our attention from the motor cortex, which controls movement execution, to the posterior parietal cortex (PPC), which controls movement planning,” says Keck School of Medicine neurosurgeon Dr Charles Y. Liu, who was lead surgeon on Sorto’s case. “Now we have an entirely new area in the brain that can potentially be very useful in perfecting the brain-machine interface to give patients who have suffered neurological injuries their lives back.”
Previous attempts at neural implants have often resulted in slow, jerky motions by the robot limbs they connect to. This is because we don’t really think through every detail of moving. Take drinking for example: when you drink from a bottle, do you think about bending your elbow? Not really.
“These finer details are carried out, in a way, automatically,” says Dr. Richard Andersen, who developed the algorithm that decodes Sorto’s thoughts. “If we had to think through each step, we wouldn’t have fluid movement either.”
To translate thoughts into more natural movement, a pair of micro-electrode arrays were implanted into Sorto’s PPC. Once in place, these electrodes record directly from the pattern of firing neurons, which is essentially the brain’s instruction manual. “By focusing on the intention to move, rather than movement itself we remove some of those automatic details, resulting in more natural, fluid movements,” says Andersen. Think of it like the difference between building a cabinet from scratch, and putting together one of those godforsaken (no really, though) IKEA sets. Each step along the way is still complicated, but the project as a whole has been streamlined.
“This was new territory for us,” says Andersen. “If you look at the posterior parietal cortex, it’s very complex … it looks something like spaghetti with very large noodles. And just like our fingerprints, the layout of those noodles changes from person to person.”
“Taking my first drink on my own –
that was amazing.”
Each of the arrays in Sorto’s brain contains 96 precisely-placed electrodes that, in turn, record from a different neuron in the PPC. Astoundingly, just sixteen days after surgery, he was ready to begin his training at Rancho Los Amigos, where a computer was attached directly to the ports extending from his skull, to translate the data from brain to arm.
“Some activities take more concentration than others,” says Sorto. “For some, we’ve found that having small conversations while I’m thinking helps the activity move along smoother. For some I have to be very quiet and focus. If I get frustrated, everything goes downhill really fast. Taking my first drink on my own – that was amazing. And I‘m sure everyone can relate to that, like imagine what it would feel like after thirteen years to just pick up a cold beer by yourself.”
Much to the surprise of Rancho Los Amigos staff, Sorto was able to move the limb on day one. After weeks of thinking, he has since refined his control of the arm, moving on to advanced tasks like controlling a computer cursor, making a hand-shaking gesture, and operating a blender.
“People come here with devastating injuries and loss of independence,” says neurologist Dr Mindy Aisen, who has worked closely with Sorto throughout his rehabilitation. “When they see extraordinarily complex technologies on the campus working, they are very excited. Erik’s perseverance, his general health, his mood, his ability to do things with his thoughts – they’ve helped and inspired everyone.”
“It’s giving me a new outlook at life,” adds Sorto. “To be part of this stuff, and to see there is hope out there for us. I might someday get to see this helping so many people.”
The research was published today in Science.