Rutgers University researchers have found brain cells responsible for helping people overcome fear of things they once found scary. The finding, published in Nature, could pave the way for these so-called intercalated cells in the amygdala, a brain region that processes fear, to become drug targets for treating phobias (such as fear of heights and closed spaces) as well as post-traumatic stress disorder in soldiers and others. Scientists trained two rat populations--one with these cells intact and the other with them disabled--to fear a certain sound by giving them a mild shock every time it was played. After awhile, the animals would freeze in their tracks when they heard the noise, bracing for pain. The team then played the tone sans the shock. When they sounded the note again a week later, rats with healthy intercalated cells weren't bothered, whereas the others froze. The scientists believe that intercalated cells form "extinction memories," which associate something previously feared (such as an air raid siren or a car backfiring) with a harmless outcome.