Emotional mental imagery and the reduction of fear within the mind’s eye
Abstract: Mental imagery refers to sensory-perceptual experiences in the absence of external sensory input. Emotional mental imagery (i.e., imagery with emotional content) is a key feature in many mental disorders, such as the image-based intrusive memories of trauma in posttraumatic stress disorder (PTSD). However, mental imagery can also be a vehicle for emotional change. In imaginal exposure, fear-provoking events are revisited using mental imagery. Imaginal exposure is a core component in evidence-based therapies for anxiety and PTSD. Treatment development is needed, as effects are many times insufficient, accessibility is low, and the treatment is not well-tolerated by some patients. The aim of this thesis was to increase knowledge of underlying mechanisms of imaginal exposure and improve our understanding of emotional mental imagery. The thesis explored the neural underpinnings of imaginal exposure and investigated mechanisms that could enhance its effectiveness, accessibility and tolerability. To further our knowledge of intrusive memories in PTSD (i.e., involuntary mental imagery), the characteristics of trauma memory hotspots (worst moments) collected within the first hours after trauma were explored. Study I demonstrated that imaginal exposure to mental imagery of phobic (vs. neutral) stimuli robustly activated emotion-processing brain areas. Study I also revealed that a brief 10-minute session of imaginal exposure was associated with reduced fear one week later. Study II investigated the link between vividness (clarity and liveliness) of mental imagery during imaginal exposure and reduction of fear using an experimental analogue of imaginal exposure (imaginal extinction). No evidence was found that high imagery vividness during imaginal extinction was associated with better long-term reduction in physiological fear responses than lower vividness. Study III revealed that hotspots collected soon after trauma are expressed as motion-rich sensory-perceptual experiences (mental imagery) with little detail on emotion/cognition. The contributions of this thesis involve demonstrating that mental imagery has the power to elicit emotional responses at subjective, physiological and neural levels and suggesting new avenues for treatment development. Future studies should explore the benefits of briefer imaginal exposure sessions to improve the effectiveness and accessibility of imaginal exposure. Future studies should also examine if fear reduction can be obtained with less vivid imaginal exposure, which could help attenuate distress and thereby make imaginal exposure tolerable for more patients. Lastly, the dynamic and visuospatial nature of newly formed trauma memory hotspots may help elucidate mechanisms through which tasks conducted posttrauma can prevent intrusive memories.
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