More than 270,000 U.S. military service members are currently diagnosed with traumatic brain injuries that can cause memory loss. Last fall, the Defense Advanced Research Projects Agency (DARPA) asked neuroscientists to do something extraordinary: Develop an implantable device that can repair that damage and restore memory. Researchers at the University of California, Los Angeles, and the University of Pennsylvania are now gearing up to meet DARPA's challenge. Based on data collected from patients with epilepsy, they plan to develop sophisticated electrical neurostimulators that tickle regions of the brain involved in memory and return brain function back to normal. Some scientists warn that the approach may be immature, however.