Robert Gaunt at the University of Pittsburgh in Pennsylvania and his colleagues placed electrodes in the brain of Nathan Copeland (pictured), whose legs and lower arms were paralysed 12 years ago. They positioned the electrodes in the somatosensory cortex — the brain region that receives sensory information from the body — and an area of the motor cortex that controls hand and arm movement. The implanted electrodes are connected by wire to a computer and robotic arm. When sensors on the fingers of the robotic arm were touched, Copeland could tell which fingers were being stimulated — and sometimes which regions of those fingers.
Putting the electrodes in different parts of the brain, or implanting more of them, could increase the sensitivity of the robotic hand.