A lighter shade of trauma.

On the morning of Monday, August 29, 2005, Hurricane Katrina made landfall in southeast Louisiana. The levee system of New Orleans failed catastrophically. Storm surges penetrated the entire city and lingered for weeks. Hurricane Katrina became known as one of the most intense, costliest, and deadliest natural disasters ever recorded in the history of the United States. Almost exactly 3 years later, on August 31, 2008, Hurricane Gustav made landfall along the still recovering Louisiana coast. Lessons learned from Hurricane Katrina prompted one of the largest evacuations in U.S. history, with 1.9 million people leaving southern Louisiana, including 200,000 residents of New Orleans. The levees held, and although the winds crippled the power system and blew off many rooftops and trees, the damage and death toll were significantly lower than the devastating consequences of Hurricane Katrina. A recent study by Weems et al. (1) examined the course of traumatic memories in youth in New Orleans attending school in a neighborhood that sustained massive flooding during Hurricane Katrina. Their findings were unintuitive. A group of youth studied 1 month after Hurricane Gustav recalled fewer negative memories of Hurricane Katrina and demonstrated reduction in symptoms of posttraumatic stress disorder (2). Why would exposure to another devastating storm improve psychological well-being rather than aggravate it? The authors speculated this has to do with a phase of memory called reconsolidation. Memories form through a consolidation process in which longterm structural changes occur in synaptic connections of nerve cells. For the most part of the 20th century, the prevailing hypothesis was that consolidation is a one-time process for storing memories in a fixed and unchangeable form (3). During the last decade, however, robust evidence is indicating an alternative view: Not only the first formation of memory but every recall of it initiates a consolidation-like storage process, that is, reconsolidation (4). In this issue of Biological Psychiatry, Liu et al. (5) report new findings on reconsolidation of laboratory-made threat memories, which might provide a mechanistic explanation for the fading memories of individuals who survived the two hurricanes. According to the reconsolidation theory, an active memory undergoing reconsolidation might be vulnerable in two ways. At the biological level, pharmacologic agents, such as protein synthesis inhibitors (6), or cruder manipulations, such as electroconvulsive shock stimulation (7), could block various stations in the cascade of synaptic, cellular, or molecular events of reconsolidation. At the behavioral level, new information or different experiences taking place at the time of reconsolidation might infiltrate the reconsolidating memory (8). Physiologic blockade typically renders the memory inaccessible (perhaps even erased).