"We've always wondered why some people who are exposed to traumatic experiences go on to develop anxiety disorders like post-traumatic stress disorder and others do not," says Mohammed Milad, PhD, a research fellow in the MGH Department of Psychiatry, the study's lead author. "We think this study provides some potential answers."
In the classical model of conditioned fear, individuals respond with physical and emotional distress to situations that bring back memories of traumatic events. Such responses are normal and usually diminish over time, as those situations are repeated without unpleasant occurrences. But some people continue to respond with what can be overwhelming fear and may develop post-traumatic stress disorder (PTSD).
For example, it would not be unusual for a soldier who experienced a traumatic battlefield situation to become distressed when hearing noises that bring back those memories, such as the sound of a helicopter. Most commonly, repeated exposure to such sounds without additional trauma reduces or extinguishes the fearful response a phenomenon called "extinction memory." But some individuals continue to experience anxiety, along with other symptoms characteristic of PTSD, when hearing the sounds.
Prior studies in animals have suggested that the ventromedial prefrontal cortex (vmPFC) an area on the lower surface of the brain may be involved in extinction memory. The vmPFC may help to quell potentia
'"/>
Contact: Sue McGreevey
smcgreevey@partners.org
617-724-2764
Massachusetts General Hospital
11-Jul-2005