Think About It: Converting Brain Waves to Operate a Prosthetic Device

The Johns Hopkins' Revolutionizing Prosthetics team is enhancing the design and natural performance of prosthetic limbs using nerve-controlled technology.

Following an electrical accident as a teenager, Les Baugh lost both arms to amputation. When he heard about a revolutionary surgery that would give him the ability to operate a prosthetic device using his thoughts, Baugh stepped forward as a volunteer.

Developed by The Johns Hopkins University Applied Physicals Laboratory, the pioneering surgical technique is called targeted muscle reinnervation or TMR. TMR is an innovative surgical procedure providing easier and more intuitive control of prosthetic arms.

Les Baugh hands a ball to Albert Chi, M.D. Image Credit: Johns Hopkins University Applied Physics Laboratory

In 2013, surgeons performed TMR on Baugh to access nerves in his upper torso. These nerves, when connected to the limbs, also developed by the laboratory, would control their movement. With training, Baugh learned to control the prosthetic simply by thinking about an action he wanted to perform. His thoughts engaged the nerves in his upper torso, which activated the prosthetic. For instance, he would think about lifting an empty cup from a counter-shelf height to a higher shelf and the prosthetic arm obeyed.

“We take the brain’s customary electrical impulses to control a human arm and use those impulses to control something else, in this case a prosthetic arm,” Michael McLoughlin, chief engineer for research and exploration development at the Johns Hopkins laboratory, explained.

While the nerve-controlled technology is an extraordinary breakthrough, McLoughlin is quick to warn that the technology is still in its early stages.

“We’re the Wright Brothers right now in all of this brain-computer interface technology, flying from one end of Kitty Hawk to the other,” he said. “But the benefits for people with paralysis are real. The missing link between brain and limb will be replaced.”

From Battlefield to Laboratory

The Johns Hopkins’ Revolutionizing Prosthetics team—comprised of neural scientists, clinicians, technology developers, and academic and commercial partners across the U.S., Canada, and Europe—have been researching the potential in the design and natural performance of prosthetic limbs for a dozen years.

The Defense Advanced Research Projects Agency (DARPA) first funded this research because large numbers of soldiers in the wars in Iraq and Afghanistan were losing their limbs to an improvised explosive device or IED. Of the more than 50,000 U.S. troops wounded in action, approximately 2.6 percent suffered a major limb amputation, most because of an IED.

“We’re the Wright Brothers right now in all of this brain-computer interface technology, flying from one end of Kitty Hawk to the other.  But the benefits for people with paralysis are real. The missing link between brain and limb will be replaced.”
—Michael McLoughlin, Chief Engineer for Research and Exploration Development, Johns Hopkins University Applied Physicals Laboratory

The initial research focused on making a better prosthetic. The team created a prototype that allowed for eight degrees of freedom (such as up, down, to the left or right) in its natural movements, compared to the 27 degrees of freedom in the human arm. This was a marked increase beyond the existing prosthetic arms.

Tests with patients recorded and configured artificial limb movements, as well as the electrical signals used to control it. Ultimately, the Johns Hopkins team created an artificial Modular Prosthetic Limb (MPL) with 180 sensors embedded, providing 26 degrees of freedom. The MPL also had more natural control—individual finger movements—that mirrored those of a biological human hand.

Developing Dexterity

After achieving major strides in physical dexterity, the next phase of development was to control the prosthetic limb through brain commands.

The Johns Hopkins team developed a small wireless device with 100 electrodes, each capable of measuring signals from individual neurons in the brain. The device was then implanted into the cranium of a monkey to access the animal’s cortical signals. Scientists decoded the signals to determine the corresponding action and then translated them into directions that could operate the robotic arm.

When the monkey thought about moving its own arm, the robotic arm moved in the way its mind had suggested. The tests proved the ability of the device to decode motor control signals from the brain and recreate natural sensations in external devices.

Wanting to assist the lab in the next stage of its research and development, Jan Scheuermann, a Pittsburgh mother of two, volunteered to have surgery to implant the neural transmitter into her brain. Scheuermann had a genetic disease that had paralyzed her from the neck down, disrupting the neural connection between her mind and limbs. The implanted electrodes allowed her brain’s messages to maneuver a robotic arm and even conduct a flight simulation.

Another research volunteer, Nathan Copeland, also stepped forward. Copeland was paralyzed from the chest down in a car accident.

“We wired the robotic arm to Nathan’s brain, providing him with two-way electrical feedback,” McLoughlin said. “He not only could operate the device by thinking, he also received signals coming from the robotic arm, such as the feeling that his fingers had been touched. It was a real `Star Wars’ moment.”

The next goal was to attach the prosthetic limb to a person to receive information directly from the brain. A single arm amputee, Johnny Matheny, volunteered to have the prosthetic connected to remaining bone in his arm. Again, the experiment was a rousing success. Matheny’s natural-like use of the prosthetic arm drew the attention of 60 Minutes, which featured him in a segment.

A Final Round of Applause

To honor the volunteers and the Revolutionizing Prosthetics team, The Johns Hopkins University board of trustees held a meeting whereby they brought Baugh to the podium to award him with a special coin. As the board members broke into applause, he dropped the coin.

The room became uncomfortably silent for a few seconds, until Baugh explained: “I thought about clapping myself.” Simply thinking about applauding caused his hand to open and drop the coin as it moved toward a clap.

Additional research and development is underway involving both invasive and non-invasive thought-controlled devices. The latter might be embedded into a hat that would, as one would imagine in a Hollywood sci-fi movie, receive wireless messages from the brain.

“We’re in a pilot program with Facebook at the moment exploring the idea of thought-to-text,” said McLoughlin. How “Star Wars” is that, he joked. “Use the force, Luke, to text your sister.”

Russ Banham is a Pulitzer-nominated journalist and author of the book, “Defining Innovations: A History of The Johns Hopkins University Applied Physics Laboratory.”