Researchers will soon be testing the Modular Prosthetic Limb (MPL) system on human subjects, using a brain-controlled interface. Scientists and engineers developed the underlying technology under an ambitious four-year U.S. government-funded effort to create a prosthetic arm that would by far eclipse the World War II era hook-and-cable device used by most amputees. The program has already produced two complex prototypes, each advancing the art of upper-arm prosthetics.