A computer monitor in the lab of Dr. Miguel Nicolelis shows the brain activity of a monkey using a brain-machine interface.
Image credit: Shawn Rocco/Duke Health
The research is part of the "Walk Again Project" in São Paulo, Brazil, working with people that have experienced spinal cord injury as a result of car crash impact, falls, and other trauma that paralyzed their lower limbs. The program aims to help participants regain strength, mobility, and independence.
The Walk Again Project is a collaboration of more than 100 scientists from 25 countries. Their combined effort enabled a man with paralysis to kick a soccer ball during the opening ceremony of the 2014 World Cup in São Paulo using a brain-controlled robotic exoskeleton.
Led by Duke University neuroscientist Dr. Miguel Nicolelis, co-director of the Duke Center for Neuroengineering, the research follows on from previous studies by Dr. Nicolelis investigating how populations of brain cells represent sensory and motor information and how they generate behavior, including movements of upper and lower limbs.
Previous studies paved the way for brain-machine use in humans
In one study, Dr. Nicolelis recorded brain activity of rats trained to pull a robotic lever to get a sip of water with the use of brain-implanted microelectrodes. Using a brain-machine interface allowed the rats to learn to control the lever using only their brain activity.
Another study saw rhesus monkeys learning to control robotic limbs and an animated version of themselves on a digital screen, as well as move wheelchairs toward a bowl of grapes with brain activity alone. The rhesus monkeys also learned to walk on a treadmill with robotic legs controlled by their brains.
These experiments with rats and primates established a model for work in human patients whereby brain activity was recorded in patients when they used a hand to grip a ball with varied force.
"It's important to understand how the brain codes for movement," says Dr. Nicolelis. "We discovered principles of how the brain operates that we wouldn't have discovered without getting inside the brain."
"Nobody expected we would see what we have found, which is partial neurological recovery of sensorimotor and visceral functions," he adds.
The goal of the new research was to pave the way for improved prosthetics and brain-controlled devices for people that are severely physically challenged.
Recovery previously unseen in long-term paralysis patients
Using brain-machine interfaces, including a virtual reality system, the patients used their brain activity to simulate full control of their legs. At the beginning of rehabilitation, five participants had been paralyzed for at least 5 years, and two had been paralyzed for more than a decade.
"What we're showing in this paper is that patients who used a brain-machine interface for a long period of time experienced improvements in motor behavior, tactile sensations and visceral functions below the level of the spinal cord injury," explains Dr. Nicolelis.
"Until now, nobody has seen recovery of these functions in a patient so many years after being diagnosed with complete paralysis," he adds.
According to Dr. Nicolelis, the participants wore a sleeve equipped with touch-technology called haptic feedback to enrich the experience and train their brains. Haptics use varied vibrations to offer tactile feedback, much like the buzzing jolts or kickbacks gamers feel through a handheld controller.
"The tactile feedback is synchronized, and the patient's brain creates a feeling that they are walking by themselves, not with the assistance of devices," says Dr. Nicolelis. "It induces an illusion that they are feeling and moving their legs. Our theory is that by doing this, we induced plasticity not only at the cortical level, but also at the spinal cord."
Diagnosis improved from complete to partial paralysis
The eight patients spent at least 2 hours a week using brain-machine interfaces, or devices controlled by their brain signals. After months of training, the scientists observed the brain activity that they expected when patients thought about moving their legs.
"Basically, the training reinserted the representation of lower limbs into the patients' brains," says Dr. Nicolelis.
After a year of training, the sensation and muscle control of four patients changed significantly enough that doctors upgraded their diagnoses from complete to partial paralysis.
Bladder control and bowel function also improved in the patients, which reduced both their reliance on laxatives and catheters and risk of infections that are common in patients with chronic paralysis and a leading cause of death.
"One previous study has shown that a large percentage of patients who are diagnosed as having complete paraplegia may still have some spinal nerves left intact," says Dr. Nicolelis.
"These nerves may go quiet for many years because there is no signal from the cortex to the muscles. Over time, training with the brain-machine interface could have rekindled these nerves. It may be a small number of fibers that remain, but this may be enough to convey signals from the motor cortical area of the brain to the spinal cord."
Dr. Miguel Nicolelis
The scientists have provided videos of the technology and patients to illustrate their progress.
Future trials will focus on patients with recent spinal cord injury to determine if quicker treatment can lead to faster and better results.