Remote-controlled rats created by scientists who used electrical implants to mobilise the paralysed animals could lead to treatments for people with spinal injuries.
The rats were paralysed by having their spinal cords severed in the middle-back so that no signals from their brains were able to reach the lower spinal cord, but by sending an electric current into spinal nerves via surgical implants scientists were able to get them to walk while held upright on a treadmill.
The team from Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland discovered that the movements could be controlled by altering the electrical signal and the animals walked over 1,000 successive steps without failure, and negotiated stairs of various heights and lengths.
EPFL neuroscientist Grégoire Courtine said: "We have complete control of the rat's hind legs. The rat has no voluntary control of its limbs, but the severed spinal cord can be reactivated and stimulated to perform natural walking. We can control in real-time how the rat moves forward and how high it lifts its legs."
The team’s results were published yesterday in the journal Science Translational Medicine and the research is part of a European project called NEUWalk to develop therapies that could one day be used in rehabilitation programs for people with spinal cord injury.
In the rat study, the scientists realised that there was a direct relationship between how high the rat lifted its limbs and the frequency of the electrical stimulation from the flexible electrodes surgically implanted at the middle-back where the spinal cord had been severed.
Combined with careful monitoring of the rat's walking patterns – or gait – the researchers were able to modify the electrical stimulation to adapt the rat's stride in anticipation of upcoming obstacles, such as barriers or stairs.
"Simple scientific discoveries about how the nervous system works can be exploited to develop more effective neuroprosthetic technologies," said co-author and neuroengineer Silvestro Micera. "We believe that this technology could one day significantly improve the quality of life of people confronted with neurological disorders."
Courtine's team has created a human-sized version of the treadmill the rats were placed on that they call the Gait Platform. It features a body support system, as well as 14 infrared cameras that detect reflective markers placed on the patient's body and two video cameras, which record information about leg and body movement.
The project aims to test the epidural electrical stimulation (EES) technology developed in the rat study on human patients with incomplete spinal cord injury as early as next summer using the Gait Platform.
"The Gait Platform is not a rehabilitation centre," said Courtine. "It is a research laboratory where we will be able to study and develop new therapies using very specialised technology in close collaboration with medical experts here at the CHUV (Lausanne University Hospital), like physiotherapists and doctors."
Courtine and Micera, together with colleagues from EPFL's Centre for Neuroprosthetics, are also exploring the possibility of decoding signals directly from the brain about leg movement and using this information to stimulate the spinal cord.