Hørlyck, Lone Diana; (2018) Effects of post-encoding processing on deliberate and intrusive memory for traumatic material. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Following a traumatic event, some individuals might experience distressing involuntary thoughts and imagery, as seen in post-traumatic stress disorder. It is crucial to understand the complex factors that contribute to the occurrence and subsequent treatment of these intrusions. Whilst it has been shown that various factors during the immediate aftermath of an event can alter successful memory storage, little is known about how such post-encoding processes influence intrusive memories for traumatic material. Accordingly, unitary accounts suggest that intrusions behave like strong voluntary memories, whereas a dual representation view predicts that they behave in a complementary way. This thesis investigated post-encoding processing for traumatic material using behavioural and functional magnetic resonance imaging (fMRI) methods. First, I examined methodologies for assessing intrusive memories in a laboratory setting, demonstrating that short video clips as an analogue trauma induced more intrusions than negative static images. Utilising this method in Chapter 3, I investigated memory for videos immediately followed by either a short break or a second, unrelated video. In two similar experiments, differences between conditions were non-significant. However, when collapsing data across the two studies to gain more power, I showed that deliberate memory performance was significantly reduced for videos immediately followed by another video compared to videos followed by a short break, suggesting disrupted consolidation for the first video. Chapter 4 examined the effects of brief wakeful rest following viewing of traumatic material, a technique thought to enhance consolidation. Here, I demonstrated that, compared to a working memory task, brief wakeful rest decreased intrusive memories and had different effects on deliberate and intrusive memory. In Chapter 5, I used fMRI to show that activity in medial temporal lobe structures, during encoding and its immediate aftermath, predicts deliberate memory, whereas amygdala activity during encoding is associated with memory intrusions. The findings from this thesis highlight the importance of the period in the aftermath of trauma and how its modulation can alter deliberate and intrusive memory in different ways.

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