Caltech is part of a team developing a “bionic suit” that will enable paraplegics to walk and feel movement by harnessing their brain waves

Loss of the ability to walk is one of the most devastating consequences of spinal cord injuries, destroying paraplegics’ independence and sense of agency. But all of that is about to change as fantasy becomes fact.
Scientists and physicians from three Southern California universities recently received an $8 million grant from the National Science Foundation (NSF) to collaboratively develop a mind-controlled “bionic suit,” similar in concept to Tony Stark’s Iron Man suit, enabling paralyzed people to walk and feel the movement.
Pasadena-based Caltech, USC’s Keck School of Medicine and UC Irvine share the five-year award, an NSF Cyber-Physical Systems Frontier grant, to fund development of an implantable brain-machine interface device designed to restore ability to walk and sensation in the lower extremities. The brain-machine device will transmit commands to a prosthetic exoskeleton for walking, enabling a paralyzed patient to walk by intention and loop sensory information back to the brain, thereby restoring lower extremity sensation information — or the feeling of walking — to the brain.
Caltech neuroscientist Richard Andersen, director of the new Caltech Tianqiao and Chrissy Chen Brain-Machine Interface Center (named for its Singapore-based benefactors), will lead the Caltech team in developing the brain-machine interface for controlling prosthetic legs. Andersen and colleagues first reported successfully implanting a device in the brain of a paralyzed man in 2015, which enabled the
patient to move a robotic arm with his mind. Andersen has devoted years of research to encoding the region of the brain that governs movement, including the posterior parietal cortex, a cognitive area that encodes the intention to move. He was unavailable for an interview, but he explained his team’s role in the revolutionary and innovative collaboration in a prepared statement about the NSF award:
“People with spinal cord injuries do not have sensation in their legs and must look at their feet when using manually controlled prosthetic legs since they do not receive normal sensory feedback,” said Andersen. “The brain-machine interface we are working on will be bidirectional: it allows neurons to control an exoskeleton and also gives neurons the feedback of sensation in the region of the brain’s cortex where the leg is represented. The stimulation-based sensory feedback is the main component of our lab’s involvement in the project.”
The first phase will involve decoding the brain signals that command the legs to walk, an effort that will be overseen by the principal investigator for the USC team, Dr. Charles Lui, professor of clinical neurological surgery and director of the USC Neurorestoration Center. To gather brain recordings of walking, Lui said, the study will recruit epilepsy patients who have undergone a presurgery workup that involves having electrodes implanted in their brain so doctors can locate where in the brain the seizures originate. Patients will be asked to walk for five minutes, Lui said, during which time their brain signals for walking will be recorded and collected for the project.
“This is a great opportunity to use some of these recordings of the brains to help more people,” Lui said in an interview. “It has to be decoded and the electronics have to be refined in a way so that paralyzed people are not walking around with a heavy cumbersome exoskeleton suit. This particular project, this robot exoskeleton, this whole concept is something teams of people have been working on for years.”
The decoded brain signals gathered from epileptic patients will be used to control a wearable robotic exoskeleton designed by the UCI team, led by principal investigator Payam Heydari, professor of electrical engineering and computer science, Zoran Nenadic, professor of biomedical engineering and Dr. An Do, assistant professor of neurology at the UCI School of Medicine. Heydari, an expert in analog circuit design, will be creating an implantable system that will enable people with spinal cord injuries to walk and regain the sensation of feeling in their legs by bypassing the damaged spinal cord.
“I am designing a revolutionary integrative circuit in nanoscale for brain-signal acquisition that can be implanted into the brain and that can send that signal from the brain to the prosthesis,” said Heydari, who added that healthcare for people with spinal cord injuries costs the U.S. $50 billion a year. “The size is important, obviously, but most important is being able to operate in the harsh environment of the brain where you have all these biochemical signals.”
Do, an expert in neurorehabilitation, will work on understanding how the brain governs walking and not walking. “My role is to understand — in those people who are paralyzed whose brain turns off during a period of time — if we can turn that brain back on with biofeedback,” said Do, who added that he will be conducting clinical testing after the brain device is implanted in paralyzed patients.
A proof-of-concept study conducted by the UCI team in 2015 helped the three universities win the $8 million award. The UCI team tested an electroencephalogram-based system on a man who had been paralyzed for seven years and whose brain was able to send messages directly to his legs, commanding them to walk. But the system was cumbersome, with the EEG-based system attached to his head via a cap; the man was suspended five centimeters from the ground to demonstrate walking motion without needing to bear weight.
“The idea is to think walk, and then the robotic exoskeleton does it,” said Lui, adding that the team expects to have a prototype in five years. “It is a really daunting engineering challenge to do this. The collaboration that exists between all of us had been ongoing for years, the walking project between USC and UCI and the artificial sensation with Caltech with the bidirectional brain-computer interface” that not only allows neurons to control the exoskeleton but also generates a signal of sensation in the brain’s cortex, which governs voluntary movement.
Until now, people living with paralysis have been able to relive walking and feeling their limbs only in vivid dreams. The creation of a neurally integrated bionic exoskeleton would be a life-changing assist for the 250,000 Americans currently living with spinal cord injuries. The National Institute of Neurological Disorders and Strokes reports that 12,000 people suffer these injuries yearly, and 80 percent of those stricken are men.
“This is an exciting emerging concept of neurorestorative medicine and this robot exoskeleton is an entirely new approach,” said Lui. “This exoskeleton is analogous to giving a human wings to fly.”