A woman paralysed in all four limbs has shown that she can move a prosthetic arm with unprecedented precision using only her brain to control the arm.

Credit: THE LANCET/ELSEVIER

Andrew Schwartz at the University of Pittsburgh in Pennsylvania and his colleagues implanted two microelectrodes into the woman's motor cortex, the part of the brain responsible for initiating movement. The devices recorded cortical activity associated with her desire to move the robotic arm. An external decoder connected to the electrodes and the arm converted these signals into electronic instructions for the limb.

The woman began training to use the arm (pictured) — which has wrist-joint movement comparable to that of a human hand — less than two weeks after implantation. Within two days she could make simple movements, and within 13 weeks she could grasp and move objects almost as fast, smoothly and accurately as an able-bodied person.

Lancet http://dx.doi.org/10.1016/S0140-6736(12)61816-9 (2012)