Slanted electrode implant restores movement to paralyzed limbs

Two examples of the Utah Slant Electrode Array that could help restore movement to those suffering limb paralysis as a result of spinal cord injury(Credit: Oregon State University)

Once the realm of science fiction, the ability to restablish a link between the brain and the limbs after it's been severed as a result of spinal cord injury is slowly becoming a reality. Now a team of researchers at Oregon State University (OSU) is working on a way to restore movement to paralyzed patients by means of tiny arrays of implantable electrodes. The team has demonstrated the electrodes' potential in a cat, which provides hope not only for those with spinal cord injuries, but also people with prosthetic limbs.

According to OSU, the frustrating thing about most paralysis cases is that the brain, muscles, and nerves are still healthy, but the connection with the brain has been severed – usually at the spinal cord. Since the nerves in the cord can't heal, the next best thing is to find a way to work around the break to restore movement.

OSU's approach involved sending precisely controlled electrical impulses to the plantar-flexor muscles in an ankle of an anesthetized cat using a 16 mm2 (0.02 in2) 100-electrode array called a Utah Slanted Electrode Array (USEA). This array is slanted to connect to different nerve layers and was embedded in the muscle nerves of the cat's ankle.

The electrode was then connected to an optimized Proportional-Integral-Velocity (PIV) controller (a form of servo controller that allows for precise output control) to send the impulses. According to the team, the PIV controller was able to send specific impulses to specific nerves, allowing the scientists to make the cat's ankle move with smooth, effortless motions.

The hope is this system could be adapted so a patient could wear a smartphone-sized control box that would provide impulses to the peripheral nerves and restore some movement.

"Say someone is paralyzed and lies in bed all day and gets bed sores," says V John Mathews, professor of electrical engineering and computer science. "Early versions of this technology could be used to help the person get up, use a walker and make a few steps. Even those kinds of things would have an enormous impact on someone's life, and of course we'd like people to do more. My hope is in five or 10 years there will be at least elemental versions of this for paralyzed persons."

Other applications could be to use the system with direct brain implants that could not only control paralyzed limbs, but also to operate mechanical prostheses. In addition, it could be used as a diagnostic tool to determine the health of nerves and muscles.

The research was published in Frontiers in Neuroscience.

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