Image credit: Courtine Lab/Ecole Polytechnique Federale de Lausanne
By Sarah Fecht
Like a severed telephone line (from back in the days when phones had wires), a spinal cord injury can cut off communication between the brain and the rest of the body — leaving a victim unable to move some or all of his or her limbs. It’s one of the leading causes of paralysis in the United States, and the debilitating effects often can be permanent.
But over the past few years, scientists have begun to overcome some kinds of paralysis using epidural electrical stimulation, or EES for short. With this technique, researchers implant two electrode arrays onto the spine: one above the injury, and one below. Then the top array reads the electrical commands from the brain and beams them to the lower array. The lower array then relays the message to the nerves that control the limbs. Essentially, the EES is a bridge that bypasses the spinal cord injury. The technology has already given paralyzed rats — and even people — the ability to walk again.
The trouble with current EES technology is that the arrays send out an electrical signal that never varies unless it’s manually adjusted. This lack of variation appears to cause the nerves to fatigue after a while. Eventually they just stop firing, and the person stops walking once again. Now scientists from the École Polytechnique Fédérale in Lausanne, Switzerland, have found a wayto vary the EES signal so that patients — or in this case, rats — can walk longer and with greater control of their steps.
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