Two paralyzed monkeys found themselves walking on treadmills thanks to a wireless brain implant developed by scientists in Switzerland. Rather than try to repair the damaged spinal cord pathways, scientists tried something different: creating a bridge of communication between the brain and the legs. The implant helps reestablish the lost connection through real-time, wireless technology.
Instead of trying to repair the damaged spinal cord pathways that usually deliver brain signals to the limbs, scientists tried an innovative approach to reverse paralysis: Bypassing the injury bottleneck altogether. The implant worked as a bridge between the brain and the legs, directing leg motion and stimulating muscle movement in real time, says Tomislav Milekovic, a researcher at Switzerland’s École Polytechnique Fédérale de Lausanne (EPFL). Milekovic and co-authors report their findings in a new paper published Wednesday in the journal Nature.
When the brain’s neural network processes information, it produces distinctive signals—which scientists have learned to interpret. Those that drive walking in primates originate in the dime-sized region known as the motor cortex. In a healthy individual, the signals travel down the spinal cord to the lumbar region, where they direct the activation of leg muscles to enable walking.
If a traumatic injury severs this connection, a subject is paralyzed. Although the brain is still able to produce the proper signals, and the leg’s muscle-activating neural networks are intact, those signals never reach the legs. The researchers managed to reestablish the connection thorough real-time, wireless technology—an unprecedented feat.
How does the system work? The team’s artificial interface begins with an array of almost 100 electrodes implanted in the brain’s motor cortex. It’s connected to a recording device that measures the spiking of electrical activities in the brain that control leg movements. The device sends these signals to a computer that decodes and translates these instructions to another array of electrodes implanted in the lower spinal cord, below the injury. When the second group of electrodes receives the instructions, it activates the appropriate muscle groups in the legs.
For the study, the two Rhesus macaque monkeys were given spinal cord injuries in the lab. After their surgeries, they had to spend a few days recovering and waiting for the system to collect and calibrate necessary data on their condition. But just six days after injury, one monkey was walking on a treadmill. The other was up and walking on post-injury day 16.
The success of the the brain implant demonstrates for the first time how neurotechnology and spinal cord stimulation can restore a primate’s ability to walk. “The system restored locomotor movements immediately, without any training or re-learning,” Milekovic, who engineers data-driven neuroprosthetic systems, told Smithsonian.com.
“The first time we turned the brain-spine interface on was a moment that I’ll never forget,” added EPFL researcher Marc Capogrosso in a statement.