At age 16, German Aldana snaped his spine just below his neck. For the next five years, he could move only his neck, and his arms a little. Researchers with the Miami Project to Cure Paralysis carefully opened Aldana's skull and, at the surface of the brain, implanted electrodes. Then, in the lab, they trained a computer to interpret the pattern of signals from those electrodes as he imagines opening and closing his hand. The computer then transfers the signal to a prosthetic on Aldana's forearm, which then stimulates the appropriate muscles to cause his hand to close. The entire process takes 400 milliseconds from thought to grasp.