A man paralyzed by gunshot more than a decade ago can shake hands, drink beer and play “rock, paper, scissors” by controlling a robotic arm with his thoughts. In a clinical trial, researchers from Caltech and Keck Medicine of USC have successfully implanted a device in a patient with quadriplegia, giving him the ability to perform a fluid hand-shaking gesture using a separate robotic arm.Two years ago, a pair of tiny chips were implanted into the brain of Erik Sorto that decoded his thoughts to move the free-standing robotic arm. The 34-year-old has been working with researchers and occupational therapists to practice and fine-tune his movements.

It’s the latest attempt at creating mind-controlled prosthetics to help disabled people gain more independence. In the last decade, several people outfitted with brain implants have used their minds to control a computer cursor or steer prosthetic limbs.

The Study

Doctors at the University of Southern California implanted small chips into Sorto’s brain during a five-hour surgery in 2013. The sensors recorded the electrical activity of about 100 brain cells as Sorto imagined reaching and grasping.

Researchers asked Sorto to think about what he wanted to do instead of breaking down the steps of the movements, said principal investigator Richard Andersen at California Institute of Technology.

After weeks of imagining movements, Sorto trained with Caltech scientists and therapists to move the robotic arm, starting with a handshake and graduating to more complicated tasks. The sensors relayed their signals to the arm, bypassing Sorto’s damaged spinal cord.

Previous research targeted a region of the brain known as the motor cortex, which controls movement. The new work zeroed in on a different area of the brain — the posterior parietal cortex — that’s involved in the planning of movements. The hope is that this strategy will lead to smoother motions.

It’s unclear whether the new approach is better because no side-by-side comparisons have been made yet, but it gives researchers a potential new target in the brain.

In 2012, a Massachusetts woman paralyzed for 15 years directed a robotic arm to pick up a bottle of coffee and bring it to her lips. In another instance, a quadriplegic man in Pennsylvania used a robotic arm to give a high-five and stroke his girlfriend’s hand.

Using a brain-controlled robotic arm to help himself to a drink, Erik Sorto says, "This study has been very meaningful to me. As much as the project needed me, I needed the project. The project has made a huge difference in my life. It gives me great pleasure to be part of the solution for improving paralyzed patients' lives." Credit: Spencer Kellis and Christian Klaes, Caltech
Using a brain-controlled robotic arm to help himself to a drink, Erik Sorto says, “This study has been very meaningful to me. As much as the project needed me, I needed the project. The project has made a huge difference in my life. It gives me great pleasure to be part of the solution for improving paralyzed patients’ lives.”
Credit: Spencer Kellis and Christian Klaes, Caltech

Sorto’s Story

Since suffering a gunshot wound 13 years ago, he longed to drink a beer without help. The first time he tried with the prosthetic arm, he was so excited that he lost his concentration and caused the arm to spill the drink. On the second try, he directed the arm to pick up the bottle and bring it to his mouth where he sipped through a straw.

The beer tasted “like a little piece of heaven,” Sorto said.

The Future

Currently, wire connections run from a patient’s brain to outside the skull, increasing the risk of infections. Future systems need to be wireless and contained within the body like pacemakers, experts J. Andrew Pruszynski of Western University in Canada and Jorn Diedrichsen of University College London wrote in an accompanying editorial. Also, computer programs must run faster to interpret brain signals and the brain implants must be more durable.

Over time, the researchers hope to improve the system so that more meaningful and practical movements can be executed which will help patients perform daily activities.