Characteristically arising in response to overwhelmingly terrifying events, post-traumatic stress disorder (PTSD) is a disorder of memory: sufferers seemingly relive their trauma in the form of involuntary recollection. Prominent cognitive abnormalities, especially in memory functioning, have motivated research designed to elucidate the mediating mechanisms that produce PTSD symptoms, especially those involving involuntary recollection. Recent developments suggest a pathophysiological model of PTSD which includes hyporesponsive prefrontal cortical regions and/or a hyper-responsive amygdala. Other work has also identified above-average cognitive ability as a protective factor and below-average hippocampal volume as a vulnerability factor for PTSD among the trauma-exposed. These attempts to elucidate the mediating mechanisms of PTSD have been both cognitive and, more recently, cognitive-neuroscientific in emphasis.