Reduced Memory Coherence for Negative Events and Its Relationship to Posttraumatic Stress Disorder

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Posttraumatic stress disorder (PTSD) is characterized by disruptions in memory, including vivid sensory images of the trauma that are involuntarily reexperienced. However, the extent and nature of disruptions to deliberate memory for trauma remain controversial. A unitary account posits that all aspects of memory for a traumatic event are strengthened. In contrast, a dual-representation account proposes up-modulation of sensory and affective representations of the negative content and down-modulation of hippocampal representations of the context in which the event occurred. We take a neuroscientific approach and review the literature concerning the mechanisms required to produce coherent episodic memories and how they are affected in experiments involving negative content. We find, in healthy volunteers, that negative content can reduce associative binding and the coherence of episodic memories. Finally, we bring these findings together with the literature on PTSD to highlight how similar associative mechanisms are affected in patients, consistent with hippocampal impairment, supporting a dual-representation view of disrupted memory coherence.