Neural correlates of recovery from post-traumatic stress disorder: a longitudinal fMRI investigation of memory encoding.

Post-traumatic stress disorder (PTSD) is characterized by a failure of psychological recovery from a traumatic experience. At a neural level, it is associated with abnormalities of the areas of the neural system that process threatening information, including the amygdala and medial-prefrontal cortex, as well as of that involved in episodic memory, including the hippocampus. However, little is known about how the function of these regions may change as one recovers from the disorder. In this investigation, PTSD patients underwent two functional magnetic resonance imaging (fMRI) scans, 6-9 months apart, while viewing fearful and neutral faces in preparation for a memory test (administered outside the scanner). At Time 2, 65% of patients were in remission. Current symptom levels correlated positively with memory-related fMRI activity in the amygdala and ventral-medial prefrontal cortex (vmPFC). In addition, the change in activity within the hippocampus and the subgenual anterior cingulate cortex (sgACC) was associated with the degree of symptom improvement (n=18). These results suggest differential involvement of structures within the fear network in symptom manifestation and in recovery from PTSD: whereas activity within the amygdala and vmPFC appeared to be a marker of current symptom severity, functional changes in the hippocampus and sgACC reflected recovery. These results underscore the importance of longitudinal investigations for the identification of the differential neural structures associated with the expression and remission of anxiety disorders.