WASHINGTON - When one leg does the walking, it evidently does some talking to the other leg as well, U.S. researchers said on Friday.
They said patients whose spinal cords were severed were nonetheless able to move their legs with the help of therapists.
And when one leg moved, it stimulated the other to move -- all without input from the brain, the research team at the University of Michigan and the University of California at Los Angeles said.
Writing in the journal Spinal Cord, they said they had added to a growing body of research that shows patients with a severe spinal cord injury can generate the muscle activity necessary to walk, independent of brain signals.
Dan Ferris, an assistant professor of kinesiology at the University of Michigan, did the work with colleague Susan Harkema while both were postgraduate students at University of California at Los Angeles.
Ferris stressed that the five patients in his study were not really walking, but were moving on a treadmill with the help of a therapist.
“But what we can get is the beginning of muscle activity,” he said in a telephone interview.
''Like a mini-brain''
What is going on is somewhat akin to a chicken running around after its head has been cut off. While most muscles move only when told to do so by the brain, many reflexes can be coordinated by the spinal cord.
“Inside the spinal cord there are a bunch of neurons put together like a mini-brain,” Ferris said. These can act in a similar way to the brain to coordinate movement.
A conscious decision to move is not always needed, he added. Sensory feedback can stimulate movement.
“Every time you take a step, the skin on the bottom of your feet takes in information related to the foot hitting the ground, muscles take in information that they are being stretched, and this goes to the spinal cord,” he said.
But the patients, many of whom had been paralyzed for years and had severely atrophied muscles, were unable to do this on their own, Ferris cautioned.
“You need to start the legs moving. We have therapists that assist the patient,” he said.
“But then the sensory information from the foot hitting the ground and the leg moving through the swing phase sends information back to the spinal cord,” he added.
Electrodes showed that when one leg moved, the nerves were stimulated in the other leg.
“We were able to move one leg and the other leg was getting information,” Ferris said. “Nobody has been able to show that in humans before.”
Ferris said he will use the work to try and develop leg braces that could help a patient with spinal cord injuries to move.