Brain implant senses 'intent' to move robotic arm

A new kind of brain implant senses a patient's intent to move a robotic arm, offering new promise to people who are paralyzed or have lost limbs, researchers said Thursday.

Erik Sorto, 34, is "the first person in the world to have a neural prosthetic device implanted in a region of the brain where intentions are made," said the study in the journal Science.

Sorto, who was paralyzed from the neck down at age 21 after a gunshot wound, can now make a hand-shaking gesture, grab a cup to drink from and even play "rock, paper, scissors" with his robotic arm.

Previous attempts to use brain implants to control prosthetics have been placed in the motor cortex, which controls motion.

This experiment was done by placing two micro-electrode arrays in the posterior parietal cortex, or PPC. This part of the brain processes plans for movements including reach and grasp.

"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," said principal investigator Richard Andersen, professor of neuroscience at Caltech.

"Instead, you think about the goal of the movement, for example, 'I want to pick up that cup of water.' 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 a myriad of components."

-- More fluid movement--

The result is a more fluid movement than the jerky kind of motions seen in previous experiments, scientists said.

Sorto received the brain implant in 2013 and has been practicing with it at Rancho Los Amigos National Rehabilitation Center ever since, learning to control a robotic arm that is not attached to his body.

He was able to control the arm in his very first attempt, about two weeks after his brain surgery.

Video images released by the science team show Sorto controlling a computer cursor, drinking a beverage and making a hand-shaking gesture with the arm.

"I was surprised at how easy it was," said Sorto, a single father of two.

"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. I really miss that independence," he added.

"I think that if it were safe enough, I would really enjoy grooming myself -- shaving, brushing my own teeth. That would be fantastic."

The clinical trial was a collaboration between Caltech, the Keck School of Medicine of the University of Southern California (USC) and Rancho Los Amigos National Rehabilitation Center.

"These very important early clinical trials could provide hope for patients with all sorts of neurologic problems that involve paralysis such as stroke, brain injury, ALS and even multiple sclerosis," said co-author Christianne Heck, associate professor of neurology at USC.