Trauma and Disorders of Memory

This chapter describes conditions under which people remember traumatic events: most quite clearly, some barely at all, while a minority remembers such events pathologically well. The account outlined here is based on the central premise that acute and chronic stressors, acting through the sympathetic-adrenal-medullary (SAM) and hypothalamic-pituitary-adrenal (HPA) systems, modulate brain systems to change the ways in which experience is transduced, distributed, stored, retrieved and integrated, reaggregated, and used. We start with a discussion of contextualized remembering, separating the concept of context into two distinct entities: settings and situations. We argue that a person's perception of setting and situation is filtered through individual differences reflecting genetic predispositions (traits), acquired characteristics (habits), and acute motivational states. We then outline remembering under normal circumstances. We then disambiguate the concepts of fear, stress, and trauma. Fear, we claim, is a state triggered through extant traits, states, and acquired characteristics mediated through the SAM axis. Once triggered, fear can bleed into stress, mediated through the HPA axis, which, under specific circumstances, bleeds into trauma. We discuss the neural bases of settings, situations, fear, and stress and discuss the representational structures the brain generates under both normal and stressful conditions. These considerations offer a way of understanding the nature of memory for trauma and suggest a resolution of recent debates in the trauma memory literature.