In 2008, a truck lost its large cargo while on the road. One of the tables on the back of it hit 21-year old Adam Fritz, and knocked him off his motorcycle and on to the freeway. Two days later, he was paralyzed from the waist down. Fritz’s spinal cord injury severed the nerves that transfer signals from his brain to his limbs.
In 2014, researchers at the University of California in Irvine started developing a system that helps paraplegic patients walk again using their brain waves. Fritz was their first test subject. He learned to use a Brain-Control-Interface (BCI) to send signals from his brain to electrodes on his knees. These signals bypass the severed region of his spinal cord to the healthy ones.
Fritz participated in a rigorous training session to master the use of BCI, and to rebuild his leg muscle tone. The BCI training went on for 19-weeks. In the training, Fritz practiced walking in a virtual reality world. He wore a special electroencephalogram (EEG) to navigate an avatar, while his brain waves were monitored. On Fritz’s 20th session, he walked a 3.5 metre course, with help from a walking frame.
Prior to this session, he practiced walking while suspended 5cm above ground. This allows him to move his legs freely without worrying about his weight. With the system, the wireless computer can differentiate Fritz’s brain wave commands. It knows when to stand still and when to walk. These commands are transferred to a micro-controller on his belt, and the nerves that trigger leg movement.
Dr. An Do, one of the researchers on this project, spoke to Radio 4’s Programmes about the process and development of this system.
“When the computer detects that a person is walking, based on these brain waves, it turns on the electrical stimulator, which starts creating muscle contractions in the right leg first, and then the left leg; right leg, left leg. And then it keeps on doing this automatically until he stops thinking about walking, then it shuts it off and keeps him in a standing position. So really he has the control of a general concept of walk or not walk.”
The team at Irvine are still working out a lot of the system’s problems. They want to expand their experimental subjects to help them understand ways to make it feel more natural, precise, and easier for its users. Eventually, they hope to invent an implant-that would fit beneath the skull-to replace the cap.
One of Do’s colleagues Zoran Nenadic added this, “We hope that an implant could achieve an even greater level of prosthesis control, because brain waves are recorded with higher quality. In addition, such an implant could deliver sensation back to the brain, enabling the user to feel their legs.”
This experiment made Fritz the first person with spinal cord injury to walk without the assistance of robotic prosthetics.