Monkeys Regain Control Of Paralyzed Legs With Help Of An Implant 
 
 Enlarge this image toggle caption Alain Herzog/EPFL Alain Herzog/EPFL 
 
 A few months ago, neurosurgeon Jocelyne Bloch emerged from a 10-hour surgery that she hadn't done before. 
 
 "Most of my patients are humans," says Bloch, who works at the Lausanne University Hospital in Switzerland. 
 
 This patient was a rhesus macaque. 
 
 The monkey's spinal cord had been partially cut. So while his brain was fine and his legs were fine, the two couldn't communicate. 
 
 "Normally, the brain is giving commands, and the legs are responding to the commands through the spinal cord. When you have a spinal cord lesion, then this command is interrupted," says Bloch. 
 
 Bloch and her colleagues were testing a device that might circumvent the injured nerves and help the brain talk to the legs another way. 
 
 She placed electrodes in the part of the monkey's brain that controls leg movement, and docked a wireless transmitter on the outside of his skull. Then, she put another set of electrodes along the spinal cord, below the injury. She also implanted an instrument in one leg so they could record muscle activity there. 
 
 Six days later, Bloch and her colleagues switched on a device to pick up signals from the electrodes in the monkey's brain, pass them through a computer, and then send them to the electrodes in the spine. 
 
 "In a few seconds you saw the leg moving, and that's something that would not have happened naturally," she says. Without the procedure, it would've likely taken months before the leg was able to move at all, Bloch says. Within a few days, the monkey was back on its feet. 
 
 Walking With An Implant A monkey with a spinal cord injury walks first with the implant turned off, and then with it switched on. 
 
 Its balance wasn't so good, but its brain and leg were communicating enough for the monkey to walk on a treadmill. Bloch did the same surgery in a second monkey, with similar results after two weeks. 
 
 The findings were published Wednesday in the journal Nature. 
 
 In the past, researchers have focused on getting brain signals to control machines, like a robotic arm, but this experiment was about re-establishing control over the body itself. 
 
 The group worked with rodents for 10 years before moving to experiments in monkeys for another seven years. 
 
 "Here they're kind of closing the loop, where they're driving that stimulation based on activity decoded from the brain," says Jen Collinger, a bioengineer at the University of Pittsburgh whose work focuses on getting paralyzed patients to operate robotic arms. 
 
 "It seems the principles learned in rats are now translating into primates," says Collinger, who was not involved in the study. "And that gives more confidence that it might also translate into humans." But, she says, there are still some major hoops to jump through. For example, it's unclear if the technology would work long-term, or if it would support the balance and weight-bearing required with walking on two feet. 
 
 Researchers in the Swiss study agree. 
 
 Enlarge this image toggle caption Alain Herzog/Swiss Federal Institute of Technology (EPFL) Alain Herzog/Swiss Federal Institute of Technology (EPFL) 
 
 "It will take at least another decade in order to achieve the full translation in humans, with no guarantee whatsoever that it will be a successful endeavor," says Gregoire Courtine, a neuroscientist at the Swiss Federal Institute of Technology and a co-author of the study. 
 
 In an accompanying commentary, Andrew Jackson of the Institute of Neuroscience at Newcastle University in the U.K. pointed out that researchers have recently come up with some pretty incredible devices — like those allowing people to control computers and robots with their thoughts — but have not been able to create a self-contained, wireless connection between human brain and limb. 
 
 Still, Jackson points out, the pace of translating technology like this from primates to humans has been remarkably quick. 
 
 "It is therefore not unreasonable to speculate that we could see the first clinical demonstrations of interfaces between the brain and spinal cord by the end of the decade," Jackson wrote, especially because the components described in the study already are approved for human use in Switzerland. 
 
 The Swiss group has started a clinical trial in eight people with partial leg paralysis. Two participants are now recovering from surgery where, like the monkeys, they received electrode implants in the spinal cord. Researchers want to know if the electrodes could help speed up or augment natural recovery in people with partially damaged nerve connections. ||||| For more than a decade, neuroscientist Grégoire Courtine has been flying every few months from his lab at the Swiss Federal Institute of Technology in Lausanne to another lab in Beijing, China, where he conducts research on monkeys with the aim of treating spinal-cord injuries. 
 
 The commute is exhausting — on occasion he has even flown to Beijing, done experiments, and returned the same night. But it is worth it, says Courtine, because working with monkeys in China is less burdened by regulation than it is in Europe and the United States. And this week, he and his team report1 the results of experiments in Beijing, in which a wireless brain implant — that stimulates electrodes in the leg by recreating signals recorded from the brain — has enabled monkeys with spinal-cord injuries to walk. 
 
 “They have demonstrated that the animals can regain not only coordinated but also weight-bearing function, which is important for locomotion. This is great work,” says Gaurav Sharma, a neuroscientist who has worked on restoring arm movement in paralysed patients, at the non-profit research organization Battelle Memorial Institute in Columbus, Ohio. 
 
 The treatment is a potential boon for immobile patients: Courtine has already started a trial in Switzerland, using a pared-down version of the technology in two people with spinal-cord injury. 
 
 “This study helps to open exciting new pathways to clinical studies and new bioelectronic treatment options for patients living with paralysis,” says bioengineer Chad Bouton, who researches medical devices used to bypass spinal-cord injuries at the Feinstein Institute for Medical Research in Manhasset, New York. 
 
 From rats to primates 
 
 The experiments are more of a progression than a sudden breakthrough: they are based on a decade of work in rats, Courtine says, and the monkeys reacted in very similar ways. The team first mapped how electric signals are sent from the brain to leg muscles in healthy monkeys, walking on a treadmill. They also examined the lower spine, where electric signals from the brain arrive before being transmitted to muscles in the legs. Then they recreated those signals in monkeys with severed spinal cords, focusing on particular key points in the lower part of the spine. 
 
 Microelectrode arrays implanted in the brain of the paralysed monkeys picked up and decoded the signals that had earlier been associated with leg movement. Those signals were sent wirelessly to devices that generate electric pulses in the lower spine, which triggered muscles in the monkeys' legs into motion. 
 
 “The whole team was screaming in the room as we watched,” says Courtine, who has seen many failed experiments to restore walking ability. The rhythm of the leg movement was imperfect, but the monkeys’ feet were not dragging and the movement was coordinated enough to support the primates’ weight. 
 
 Adapted from A. Jackson Nature 539, 177–178 (2016) 
 
 Researchers have previously used brain-reading technology to enable paralysed people to move a robotic arm, give themselves a drink or to move their own hand and play a video game. The brain signals involved in activating muscles in a paralysed leg are less complex than those that guide the hand and all its digits, says Courtine. But researchers studying arm and hand movement have the advantage that even incremental improvements are useful. 
 
 “A small improvement in the ability to grasp changes your quality of life, but ‘almost walking’ doesn't help much,” Courtine says. “With the legs, it’s all or nothing.” He is now working with monkeys to try to ensure better leg-muscle control, so that the primates can not only support their own weight but also maintain their balance and avoid obstacles. 
 
 Human applications 
 
 Doing the same thing with humans will be more complex, says Courtine: the brain decoding is much more complicated. The primate study, for example, used electrical activity recorded from the spinal cord before the injury and “played it back” to restore movement, notes Bouton. “That’s an approach that wouldn’t be practical after an actual spinal-cord injury,” he says. 
 
 And Sharma says that further research will have to take into account other elements of walking. Rhythmic coordination of gait, for example — which the monkeys didn’t demonstrate — is controlled by a different group of neurons. Devices to enable human locomotion in paralysed patients would ideally include brain–computer interfaces, electrical stimulation for activating muscles, an exoskeleton-like device to help bear weight, and smarter electrical processing to enable gait control, he says. 
 
 Courtine has started a clinical trial at the CHUV University Hospital of Lausanne, geared towards rehabilitation by helping to stimulate coordinated walking in people who are paralysed. Two people have had the electric-pulse generators implanted in their lower spines. (The trial will not implant microelectrode arrays in the people's brains, however, so they will not be able to control the movement themselves.) 
 
 As clinical trials proceed in Switzerland, Courtine is still regularly travelling back to China. Although the positive results have allowed him to negotiate the use of five monkeys at a Swiss primate laboratory, some of his experimental work still takes place in Beijing. China’s welcoming attitude to primate research will reap benefits for the country, Courtine says. “This is going to provide China with a tremendous leverage for translational medicine.”
– In what could someday prove to be a major step forward for people with spinal cord injuries, scientists out of Switzerland are reporting in the journal Nature that they've gotten paralyzed monkeys to walk again. NPR describes the surgery on the rhesus macaques thusly: A neurosurgeon "placed electrodes in the part of the monkey's brain that controls leg movement, and docked a wireless transmitter on the outside of his skull. Then, she put another set of electrodes along the spinal cord, below the injury." The idea is that the brain device beams instructions to the spine, which tells the legs to move. Using this "brain-spine interface," they used electrical activity they recorded in the monkeys' spinal cords prior to the injuries and "played it back" to restore movement. "That’s an approach that wouldn’t be practical after an actual spinal-cord injury," says the lead researcher. "The whole team was screaming in the room as we watched," the lead researcher, who travels between Switzerland and China (where regulations are more lenient on experimenting with primates) tells Nature News. Experts around the world have seen many failed experiments to restore walking over the years, and while the rhythm of the leg movement wasn't totally natural, the monkeys were able to support their weight enough to walk on a treadmill without dragging their feet. A small clinical trial is already underway in Switzerland for two people with spinal cord injuries to further test the interface. "It will take at least another decade in order to achieve the full translation in humans, with no guarantee whatsoever that it will be a successful endeavor," says the lead researcher. (Meanwhile, a monkey's head has been successfully transplanted.)