Exaggerated amygdala response to masked facial stimuli in posttraumatic stress disorder: a functional MRI study.

BACKGROUND Converging lines of evidence have implicated the amygdala in the pathophysiology of posttraumatic stress disorder (PTSD). We previously developed a method for measuring automatic amygdala responses to general threat-related stimuli; in conjunction with functional magnetic resonance imaging, we used a passive viewing task involving masked presentations of human facial stimuli. METHODS We applied this method to study veterans with PTSD and a comparison cohort of combat-exposed veterans without PTSD. RESULTS The findings indicate that patients with PTSD exhibit exaggerated amygdala responses to masked-fearful versus masked-happy faces. CONCLUSIONS Although some previous neuroimaging studies of PTSD have demonstrated amygdala recruitment in response to reminders of traumatic events, this represents the first evidence for exaggerated amygdala responses to general negative stimuli in PTSD. Furthermore, by using a probe that emphasizes automaticity, we provide initial evidence of amygdala hyperresponsivity dissociated from the "top-down" influences of medial frontal cortex.