Photograph of the Utah Slanted Electrode Array, courtesy of OSU.
Patients with spinal cord injuries (SCIs) might one day regain use of arms and legs that have been paralyzed thanks to research that demonstrated how limbs can be controlled via a tiny array of implanted electrodes. The work focused on controlling electrical stimulation pulses delivered to peripheral nerve fibers. While this particular research focused on helping people with paralysis, a related research area involves patients with limb loss using neuroprostheses to control his or her prosthetic arm or leg.
When a patient has paralysis, one of the possible causes is damage to the spinal cord. The brain is working, and so are motor and sensory nerves in the peripheral nervous system, but electrical signals can’t flow between those nerves and the brain because of the SCI. That communication problem is what researchers sought to address through experiments that involved transmitting precisely controlled electrical pulses into nerves activating plantar flexor muscles in an ankle of an anesthetized cat.
V John Mathews, PhD, professor of electrical engineering and computer science in the Oregon State University (OSU) College of Engineering; lead researcher Mitch Frankel, then a doctoral student at the University of Utah; and three other researchers, all faculty members at Utah, conducted the study. Findings were recently published in the journal Frontiers in Neuroscience.
Researchers sent the pulses using an optimized proportional-integral-velocity controller and the cat’s nerves received them via a 100-electrode array whose base measures 16 square millimeters, known as the Utah Slanted Electrode Array. Due to specific electrodes being able to activate the right nerve fibers at the right times, the controller made the cat’s ankle muscles work in a smooth, fatigue-resistant way. The results suggest that someday a person with paralysis might be equipped with a wearable, smartphone-size control box that would deliver impulses to implanted electrodes in his or her peripheral nervous system, thus enabling at least some level of movement.
“Say someone is paralyzed and lies in bed all day and gets bed sores,” Mathews said. “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…. We can learn from the brain what the intent is and then produce the signals to make the movement happen.”
Editor’s note: This story was adapted from materials provided by OSU.
