Swiss scientists say they have helped rats whose severed spinal cords left them completely paralyzed to walk again through electrical stimulation of the severed cord to move its limbs.

The experiment may one day lead to therapies offering rehabilitation for people who've suffered spinal cord injuries, scientists at the Swiss Federal Institute for Technology say.

Human trials of the technique could begin next summer, say the authors of a report on the study published in Science Translational Medicine.

Scientist have been seeking a way to mimic the signals from the brain that are blocked by the injured spinal cord and use them to directly stimulate the cord below the injury site with electrical pulses.

Experiments using this method have allowed some paraplegics to regain limited voluntary movement of their hips and legs, they say.

The drawback to this technique, the Swiss researchers not, is that it requires the frequency and amplitude of the electrical pulses to be continually adjusted, something difficult to accomplish during an attempt by a paralyzed individual to walk.

In the new study, the researchers came up with computer algorithms to automatically make those adjustments during locomotion.

In the rats, electrodes that had been surgically implanted delivered the impulses that were adjusted in real time, copying the way a brain's neurons would fire naturally.

"We have complete control of the rat's hind legs," neuroscientist Grégoire Courtine said, noting the rats could take a thousand steps and even climb staircases.

"The rat has no voluntary control of its limbs, but the severed spinal cord can be reactivated and stimulated to perform natural walking," he said.

It may be possible one day to decode signals for leg movement directly from a person's brain and use the data to stimulate a spinal cord with implanted electrodes, the researchers said.

A scaled-up human-size version of the rat experiment, dubbed the Gait Platform, will contain a treadmill with an overhead support system, plus cameras to acquire extensive information about body and leg movement, they said, and trials would begin on it next summer.

"It is a research laboratory where we will be able to study and develop new therapies using very specialized technology in close collaboration with medical experts here at the [Lausanne University Hospital], like physiotherapists and doctors."

The goal of the Gait Platform is achieve intelligent assistance and adaptive electrical spinal cord stimulation of the patient, the researchers said.