Could a device possibly enable paralyzed patients to walk? It may be feasible according to Ralph Etienne-Cummings, an electronics and robotics expert at Johns Hopkins.
Etienne-Cummings along with UMCP professor Avis H. Cohen is developing a microchip implant that may someday aid paralyzed people.
A spinal cord injury results in a loss of mobility when the nerves connecting the brain to the nerve control centers are severed. The control centers are called central pattern generators, and they guide movement from the lower back.
The goal of this collaborative study is to develop microchips that would transmit signals to nerve centers which would induce movement of muscles. It is hoped that such a device would enable patients with spinal cord injury to walk one day.
Etienne-Cummings states that such an undertaking is a long term project. In order to create such a device, the team is investigating how the brain sends impulses along the spinal cord that coordinate movement of leg muscles.
The research team is studying the anatomy of the lamprey eel to determine the relationship between the nervous system and locomotion.
Cohen, who has been studying how electrical messages control swimming in lamprey eels, states that the coordination of motion is remarkably similar in both lamprey eels and humans. Cohen also adds that "the lamprey's nervous system is remarkably easy to study." After excision from the eel, the lamprey's spinal column can be kept alive in a solution. With the addition of chemicals, the spinal cord can be stimulated to produce nerve impulses identical to those produced when the live eel is swimming.
Collaborating with M. Anthony Lewis of Iguana Robotics, Inc, the research team recently reported that the use of a microchip mimicking the signal transmission of a central pattern generator produced ambulatory movement in a robotic leg.
Following the death of actor and research proponent Christopher Reeve, an increasing number of studies aims to remedy the damage caused by a spinal cord injury.
Most scientists are trying to regenerate nerves that have been cut off or directly stimulate the areas with loss of function. Etienne-Cummings and Cohen are pursuing an unconventional route in their study. They hypothesize that central pattern generators remain functional after nerves connecting them to the brain are severed.
Etienne-Cummings and Cohen believe that an implant would function like the brain by controlling the inactive central pattern generators. If such a microchip is developed, it would be possible for the control centers to send locomotion signals to leg muscles in paralyzed patients. "We want to take advantage of circuits that already exist in the body," Etienne-Cummings was quoted as saying. "Instead of stimulating the leg muscles directly, we want to go to the spinal cord and stimulate the nerves that control the muscles in the legs."
According to Etienne-Cummings, the device would consist of mixed-signal microchips. He also expects that the implant would be powered by a rechargeable battery and be relatively small and inexpensive.
When can we expect to see these implants being put to use in paralyzed patients? It may take up to ten years according to the Etienne-Cummings and Cohen. Etienne-Cummings states that much still needs to be done, before they can test such implants in small mammals. The devices may be approved for use in humans ten or more years from now.
This long-term study is being supported by a grant from the Office of Naval Research, the NSF and NIH.
