According to new research, a tiny injectable implant that is smaller than a grain of rice might one day take the place of large neural stimulators used to treat chronic pain and other neurological disorders. Scientists say the new device works similarly to spinal-cord stimulators that use electrical jolts to override the neural pain signals being transmitted to the spinal cord. The new device is still in its very early stage of testing on rats, and some scientists are skeptical that the device...