By DAVID HELLERSTEIN, M.D."Did I tell you about my trip?" Hannah asked.Now several years into her psychiatric treatment, Hannah and I were meeting every few months. I didn't recall any recent mention of travel plans."It was my first plane ride, and we went to Mexico," she said. "It was beautiful. The turquoise water below us, all the white sand beaches ..."When I met Hannah in the early 1990's, panic attacks made it nearly impossible for her to leave her apartment. Our efforts to modify her brain's circuitry began slowly: we combined the antidepressant Zoloft with breathing and relaxation training, and challenged her catastrophic thoughts.Gradually, Hannah retook Manhattan. Getting past 34th Street, daring the subway, re-entering Bloomingdale's — her appointments became a catalog of firsts. Slowly she re-emerged into life, meeting Jorge, getting married, having two kids. Now there had apparently been another breakthrough.Given her lifelong and consuming fear of travel, I had assumed that Hannah would describe a weekend upstate, with a white-knuckled ride up the Taconic State Parkway. Instead, she was telling me how she had planned for the trip to Mexico: an extra dose of the anti-anxiety drug Klonopin that morning, diaphragmatic breathing, exercises to control her thoughts on the runway.Once aloft, she felt giddy with relief and excitement. In the successful treatment of mood and anxiety disorders, it is not uncommon, I find, for patients to take a trip. Not a harried business overnighter, not an obligatory weekend visiting parents. Instead, they book a trip that they've always dreamed about. These trips are hardly what we doctors used to call flights into health — desperate attempts to avoid suffering. Instead, they reflect one of the most mysterious phenomena encountered in psychiatry: recovery. In acute depression or panic disorder, escape may beckon, but such trips are miserable, anything but vacations. Severe symptoms usually make it necessary to hunker down at home. As recovery proceeds, though, adventures long yearned for become possible, and often irresistible.These trips, I suspect, reflect brain recovery, the reawakening of special circuits for well-being.For decades, neuroscientists have focused on the brain's fear center, the amygdala. In anxiety disorders and depression, the amygdala is hyperactive, hypersensitive, too easily sent into red alert. Fear-conditioning models (a mouse in a cage with an electrically wired floor) confirm the power of these systems.Recent research by Dr. Michael Rogan at Columbia shows that the brain also has a safety center. This center, in the region called the dorsal striatum, communicates a sense of security. While the amygdala sends off air raid sirens telling you to dive for safety, the dorsal striatum rings out, "All clear!" Dr. Rogan has re-envisioned the classic experiment. What if you condition a mouse by playing a tone when there is not going to be a shock? The mouse soon learns that it is safe when the tone sounds. Signals from the dorsal striatum's safety center connect to parts of the brain that, as Dr. Rogan puts it, "are dedicated to the processing of reward, reward contingencies or positive affective states," releasing neurotransmitters associated with pleasure like dopamine.How does this relate to travel? Normally, a mouse stays on the edges of its cage. It avoids open spaces where it would be vulnerable to predators. Only occasionally will it dart into the open, in quick forays for food. With fear conditioning, the mouse won't even dart — it hunkers down. But when a mouse gets the signal from the safety center, something very different happens. It runs into the middle of the cage, basking in its sense of freedom. It actually avoids the usually safer edges of the cage.Human analogies naturally come to mind — postgame celebrations at a football game, recess period at school. Bells ring, and we flood into usually forbidden zones.This, I believe, is where recovery from psychiatric disorders comes in. In acute disorders, people hunker down in fear, immobilized like fear-conditioned mice. As the symptoms fade, they often remain withdrawn, fearing the worst. Eventually, with encouragement, they may begin to roam freely, in what Dr. Rogan calls "appropriate adventurous exploration." Perhaps the dorsal striatum is slower to recover than the amygdala. But once it gives the all clear, the world becomes safe to explore. Now that we have imaging techniques like PET and functional magnetic resonance imaging scans, observations in therapy can lead directly to research. As Hannah put it, she was "feeling whole" and "feeling safe." Though Hannah planned and executed it on her own, her trip to Mexico was a culmination of years of psychiatric work — many therapy sessions and medication adjustments. It was indeed a flight into health, after which she — and I, her doctor — could see few limits to what she might do.