Amygdala response in patients with acute PTSD to masked and unmasked emotional facial expressions

OBJECTIVE: This study used functional magnetic resonance imaging to investigate amygdala response in patients with acute posttraumatic stress disorder (PTSD) to emotional expressions. METHOD: Thirteen medication-free individuals with acute PTSD and no axis I psychiatric comorbidity were scanned while viewing pictures of fearful or happy faces, presented above or below consciousness, with backward masking. RESULTS: There was a significant positive correlation between the severity of PTSD and the difference in amygdala responses between masked fearful and happy faces and a corresponding negative correlation for the difference between unmasked fearful and happy faces. CONCLUSIONS: These findings suggest that functional abnormalities in brain responses to emotional stimuli observed in chronic PTSD are already apparent in its acute phase.

A number of neuroimaging studies have reported enhanced activity in the amygdala—a key brain structure for emotional processing (1)—in individuals with posttraumatic stress disorder (PTSD) in relation to healthy comparison subjects in response to pictures (2), trauma-related scripts (3), and masked fearful faces (4). However, these studies were conducted on participants with long-standing chronic PTSD, which is typically associated with pharmacological treatment and significant psychiatric axis I comorbidity, including major depressive disorder and alcohol and substance abuse (5). Thus, it remains to be determined to what extent the observed results are specific to PTSD as opposed to other factors (6).

In addition, the majority of PTSD studies to date to our knowledge have focused on negative emotions; therefore, it is not known whether there are any abnormal patterns of activity in PTSD associated with positive stimuli. Thus, in this study, we examined amygdala responses to faces depicting happy and fearful expressions, presented above and below awareness, in recently traumatized individuals suffering from acute PTSD. In particular, we tested whether there were any differential responses to positive and negative emotional expressions as a function of stimulus awareness and the severity of PTSD.