Biological models propose that post-traumatic stress disorder (PTSD) reflects a failure of extinction of the conditioned fear response. Animal models and recent human imaging studies suggest that ventromedial prefrontal (vmPFC) regions inhibit amygdala fear networks during fear extinction (Rauch et al. 2006; Phelps et al. 2004). Accordingly, PTSD is associated with a failure of vmPFC activity in response to threat. Exposure-based treatments are thought to facilitate the extinction of conditioned fear. No imaging studies have examined the neural correlates of symptom improvement following exposure-based treatment in PTSD. Eight individuals with PTSD underwent functional magnetic resonance imaging (fMRI) scanning while viewing fearful and neutral facial expressions in a passive viewing task adapted to a 1.5T scanner. fMRI assessments were conducted before and after treatment. Amygdala and vmPFC (anterior cingulate) activity was examined before and after treatment in a repeated-measures, fixed-effects ANOVA and changes in these regions were correlated with changes in PTSD severity. Consistent with predictions, findings show that anterior cingulate activity increased and amygdala activity reduced to fear following exposure treatment in PTSD, and symptom improvement was correlated with increased anterior cingulate activity and reduced amygdala activity to fear. These findings provide initial support for a role of reduced vmPFC activity in PTSD that recovers following exposure treatment.
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