“THE leg wasn’t bouncing all over the table, but there were substantial twitches,” says Matthew Schiefer, a neural engineer at Case Western Reserve University in Cleveland, Ohio.

Schiefer is describing an experiment in which pulses of electricity are used to control the muscles of an unconscious patient, as if they were a marionette. It represents the beginnings of a new generation of devices that he hopes will allow people with paralysed legs to regain control of their muscles and so be able to stand, or even walk again.

His is one of a raft of gadgets being developed that plug into the network of nerves that normally relay commands from the spinal cord to the muscles, but fall silent when a spinal injury breaks the chain. New ways to connect wires to nerves (see diagram) allow artificial messages to be injected to selectively control muscles just as if the signal had originated in the brain. Limbs that might otherwise never again be controlled by their owners can be brought back to life.
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