Examining memory processes underlying intrusive trauma memories : the impact of retrieval suppression and associative learning

Field: Psychology (Social Sciences)

The global aim of this thesis was to examine the mechanisms underlying intrusive memories after traumatic events. As recent findings suggest that deficits in the ability to voluntarily inhibit memory retrieval are related to posttraumatic stress disorder (PTSD) symptom severity, the studies included in this work tested whether deficits in retrieval suppression constitute a potential cognitive risk factor that leads to an increase in intrusive memories after traumatic events. Furthermore, these studies investigated whether the same neural process that mediates retrieval suppression is also associated with fewer trauma memories. Since current research indicates that intrusive trauma memories can occur as conditioned responses to trauma reminders, another aim of this thesis was to further examine the role of conditioning in the development and maintenance of intrusive trauma memories. Specifically, the temporal stability of conditioned reactions was investigated. An additional aim of this thesis was to test whether conditioned responses are reduced after imaginal exposure, as has been suggested by current models of PTSD.\nStudy 1 was designed to test whether pre-existing deficits in memory control constitute a potential cognitive risk factor for intrusive memories after traumatic events, and whether the neural processes underlying memory control are also involved in controlling intrusive trauma memories. Suppression-induced forgetting, an index of memory control, was found to be associated with subjective distress experienced during intrusive memories of a traumatic film. Furthermore, the neural correlate of the inhibitory control process which is supposed to underlie suppression-induced forgetting (i.e. N2 ERP component) was also associated with a reduction in the degree of distress of intrusive memories, as well as a reduction in other analogue PTSD symptoms. These findings indicate that the pre-existing ability to suppress memory retrieval may be beneficial for recovering from intrusive memories after traumatic events. Furthermore, the findings indicate that the same inhibitory control process that was found to mediate retrieval suppression and stopping a prepotent motor response may also be involved in controlling the automatic retrieval of intrusive trauma memories.\nStudy 2 aimed to investigate whether conditioned responses to trauma-associated stimuli are stable over time and whether they are affected by imaginal exposure. Indeed, intrusive memories and subjective fear as a reaction to trauma-associated stimuli were observed and remained stable over the entire assessment period of one week, providing further evidence for the assumption that conditioning plays a crucial role in the development and maintenance of intrusive memories after traumatic events. Furthermore, conditionability of subjective indices was associated with subsequent ambulatory intrusive memories, however, physiological parameters assessing emotional arousal as a reaction to trauma reminders did not show these effects. Moreover, imaginal exposure had no impact on conditioned responses to trauma-associated stimuli or intrusive trauma memories.