A new report in Nature gives hopeful news about how we could recover from paralyzing spinal cord injuries in the future.
Researchers describe a rhesus monkey regaining the use of its leg just six days after a paralyzing injury. The key is a wireless “brain-computer” interface, connecting an implant in the monkey’s brain to an electrical stimulator on its spine. By translating the monkey’s movement-related brain signals into electrical pulses on its spine, the technology helps the brain give the leg instructions to move — bypassing the injured part of the spinal cord.
The study’s lead researcher, Gregoire Courtine, thinks that humans could be testing a similar interface within a decade. And across the field of spinal cord injury research, human trials are already moving forward with additional technologies, including other brain-computer interfaces and stimulation techniques. What could the near future hold?
According to Susan Harkema, who directs spinal cord injury research at the University of Louisville, scientists have known for a long time that mammals can regain movement after spinal cord injuries, with the help of stimulation or drugs. But she says the Swiss study used this knowledge in novel ways.
“What's new about this, is, they recorded signals from the brain, and they used wireless technology to send those signals after they had cut the spinal cord, and then tell the other piece of technology to send signals to help the paralyzed part of the body reactivate,” she says.
Harkema’s own research also uses spinal cord stimulation to help patients with paralysis. In 2014, her team implanted electrical stimulators in the spines of two paralyzed men, helping them voluntarily move their legs for the first time in years. Harkema says they’ve now implanted 10 individuals, with similar results. What’s more, her team found that using stimulation to restore basic standing and walking functions may have some other upsides, which they’re now exploring in some new research.
“We found that other conditions such as cardiovascular deficits, respiratory, poor blood flow, lots of other secondary conditions — bowel and bladder — seem to be positively affected by the stimulation,” Harkema says.
But one problem Harkema’s team faces is that their stimulation technique can be hard to use outside of a clinical setting. “We need to couple that with the technology to make it useful in the home and community,” she says. “That’s one of the areas of research we’re working very hard on.”
They’re not alone. The field of spinal cord rehabilitation research is full of wires, and electrical pulses and the transmission of huge amounts of data between brain and limb — hardly portable, to say the least. But the new interface used in the Swiss study could be.
“I think the wireless technology is a breakthrough,” says Bolu Ajiboye, a biomedical engineer at Case Western Reserve University. Ajiboye is part of a team that’s also using brain-computer interfaces, this time to help patients with high-level spinal cord injuries regain hand and arm movements like reaching and grasping. One interface is currently in human clinical trials, but participants are wired to their brain-recording devices, making it difficult for them to use the technology in daily life.
“For them to be able to use the systems on a regular basis, we need a system which allows us to perform 24/7 recording and that's wireless, so that that's definitely a breakthrough,” Ajiboye says.
And for paralyzed humans to truly benefit from technology like a brain-computer interface, we’ll also need to be able to record tens of thousands of neurons at once — replicating, for example, the complex commands we give our hands to reach and grasp. Ajiboye says we’re not there yet.
“Most of the current work — my work included, and the work in the paper — are fairly limited in terms of the number of neurons you’re able to record from simultaneously,” Ajiboye says. “We need high-dimensional recordings that allow us to control these high-dimensional systems.”
Against the puzzle of restoring movement to a paralyzed limb, finding a way to record more neurons (almost) sounds easy. Here’s hoping that it is.