In a collaboration that blends biology and robotics, researchers at Johns Hopkins and the University of Maryland are unraveling the circuitry in an eel's spinal cord to help develop a microchip implant that may someday help paralyzed people walk again.
After a spinal cord injury, many patients are unable to move because the brain is cut off from nerve control centers called central pattern generators, which are believed to be located in the lower back. The two-school research team's goal is to make a device that could mimic the signals sent by the brain and coax these nerve centers into sending "walking" instructions to muscles in a patient's legs.
"This is a challenging, long-term project, but we believe it has a good chance to succeed," said Ralph Etienne-Cummings, an electronics and robotics expert who is lead researcher on the project at Johns Hopkins. "Our first step is to learn how the brain transmits electrical messages along the spinal cord that tell the legs what to do. Then, we want to make microchips that replicate this process. We've started by modeling the way swimming signals move along the spinal cord of a lamprey eel."
Etienne-Cummings, an associate professor in the Department of Electrical and Computer Engineering at Johns Hopkins, specializes in designing robotic devices that operate in ways that resemble those found in biological organisms. In the spinal cord project, he is working with Avis H. Cohen, who has spent many years studying the lamprey's nervous system and how it directs swimming. Cohen is a professor in the Department of Biology, Neuroscience and Cognitive Science at the University of Maryland, College Park.
"Even though the lamprey is a very primitive vertebrate, we and others have shown that it's remarkably like humans in the ways it makes and controls its locomotion," Cohen said. "But unlike that of humans, the lamprey's nervous system is remarkably easy to study."
The recent death of actor and research advocate Christopher Reeve has increased the public's awareness of efforts to help people with spinal cord injuries. The team led by Etienne-Cummings and Cohen has already published a paper describing the use of a microchip version of a biological central pattern generator to produce a lifelike gait in a robotic leg. In this project, funded by the U.S. Office of Naval Research, the university researchers collaborated with M. Anthony Lewis of Iguana Robotics, Inc.
The researchers are now moving to expand their project by developing a neuroprosthetic implant that would connect to human central pattern generators to restore locomotion in patients with spinal cord injuries.