An fMRI investigation of memory encoding in PTSD: influence of symptom severity

Previous studies have shown memory deficits in Post-Traumatic Stress Disorder (PTSD) patients, as well as abnormal patterns of brain activity, especially when retrieving trauma-related information. This study extended previous findings by investigating the neural correlates of successful memory encoding of trauma-unrelated stimuli and their relationship with PTSD symptom severity. We used the subsequent memory paradigm, in the context of event-related functional magnetic resonance imaging, in 27 PTSD patients to identify the brain regions involved in the encoding of fearful and neutral faces. Symptom severity was assessed by the Clinically Administered PTSD Scale (CAPS) scores. It was found that memory performance was negatively correlated with CAPS scores. Furthermore, a negative correlation was observed between CAPS scores and ventral medial prefrontal cortex (vmPFC) activity elicited by the subsequently forgotten faces. Finally, symptom severity predicted the contribution of the amygdala to the successful encoding of fearful faces. These results confirm the roles of the vmPFC and the amygdala in PTSD and highlight the importance of taking into account individual differences when assessing the behavioural and neural correlates of the disorder.