CanadianRealist writes: Current prosthetic arms are usually controlled by detecting signals from the user twitching muscles in the shoulder or arm. This allows only a limited number of possible movements, such as grasp and release. Researchers have developed a new technique that interprets signals from motor neurons in the spinal cord, allowing for a greater range of control of an arm. Signals from nerves associated with hand and arm movements were mapped to the corresponding movements. Test subjects were able to move a virtual prosthetic arm with greater freedom than has been achieved with muscle-controlled prosthetics. (Note: A virtual prosthetic arm was used rather than a real one as this work is still in the early stages.) The study has been published in the journal Nature Biomedical Engineering.