The role of peri-traumatic visuo-spatial and verbal interference on the development of intrusions
Intrusions are regarded as a 'hallmark' symptom of Post-Traumatic Stress Disorder, yet relatively little is known about their formation and development. This thesis was an experimental examination of potential information processing factors implicated in intrusion development. The thesis begins with an examination of PTSD in the context of intrusions, followed by a review of the main theories of PTSD symptom development and the place of intrusion development within these. Recent theories of PTSD are examined, specifically Dual Representation Theory (Brewin, Dalgleish, and Joseph, 1996), which regards PTSD as a 'hybrid' disorder that involves two distinct yet parallel types of memory encoding one based in part on sensory, visual processing, the other on verbal/narrative based processes, the interaction of which can lead to intrusion development under certain conditions. This thesis attempted to replicate and extend research (Holmes, Brewin, Hennessy, 2004) founded on dual-representation theory, that explored the role of peri-traumatic visuo-spatial and verbal processing in the formation of intrusions based on a trauma analogue film. 40 non-clinical participants were involved either a control condition, or one of two dual-task interference conditions: a visuo-spatial interference condition (involving tapping out a key pattern of a hidden keyboard); and a verbal interference condition (involving counting backwards in threes). Participants were instructed to watch a trauma-analogue film designed to generate intrusions, whilst performing the task they were allocated. Diary measures were taken of subsequent intrusions experienced in the week following exposure to the analogue trauma film. Visuo-spatial interference appeared to significantly disrupt the formation of intrusions, while there was a trend for verbal processing to increase intrusions. The visuo-spatial interference task did not impact on attention to the film, or features of either recall or recognition of film material. For the verbal interference condition, there was also significantly more visual imagery type intrusions, more data driven processes reported, and a reduction in recall memory and attention to film. Increases in state dissociation were also implicated in higher reported intrusions. These findings were discussed in the context of current theories of intrusion formation, and in terms of clinical implications for the assessment and treatment of intrusions in PTSD.