A clinical neuroscience investigation into flashbacks and involuntary autobiographical memories

Recurrent and intrusive distressing recollections of trauma are a hallmark symptom of Posttraumatic Stress Disorder (PTSD). The term ‘flashback’ is used in this thesis to refer to vivid, sensory perceptual (predominantly visual images), emotional memories from a traumatic event that intrude involuntarily into consciousness. Furthermore, intrusive image based memories occur in a number of other psychological disorders, for example, bipolar disorder and depression. Clinically, the presence and occurrence of flashbacks and flashback type memories are well documented. However, in terms of the neural underpinnings there is limited understanding of how such flashback memories are formed or later involuntarily recalled. An experimental psychopathology approach is taken whereby flashbacks are viewed on a continuum with other involuntary autobiographical memories and are studied using analogue emotional events in the laboratory.
An initial review develops a heuristic clinical neuroscience framework for understanding flashback memories. It is proposed that flashbacks consistent of five component parts – mental imagery, autobiographical memory, involuntary recall, attention hijacking and negative emotion. Combining knowledge of the component parts helped provide a guiding framework, at both a neural and behavioural level, into how flashback memories may be formed and how they return to mind unbidden.
Four studies (1 neuroimaging, 3 behavioural) using emotional film paradigms were conducted. In the first study, the trauma film paradigm was combined with neuroimaging (n = 35) to investigate the neural basis of both the encoding and the involuntary recall of flashback memories. Results provided a first replication of a specific pattern of brain activation at the encoding of memories that later returned as flashbacks. This included elevation in the rostral anterior cingulate cortex, insula, thalamus, ventral occipital cortex and left inferior frontal gyrus (during just the encoding of scenes that returned as flashbacks) alongside suppressed activation in the left inferior frontal gyrus (during the encoding of scenes that returned as flashbacks in other participants, but not that individual). Critically, this is also the first study to show the brain activation at the moment of flashback involuntary recall in the scanner. Activation in the middle and superior frontal gyri and the left inferior frontal gyrus was found to be associated with flashback involuntary recall.
In the second study, control conditions from 16 behavioural trauma film paradigm experiments were combined (n = 458) to investigate commonly studied factors that may be protective against flashback development. Results indicated that low emotional response to the traumatic film footage was associated with an absence of flashbacks over the following week. The third study used a positive film to consider the emotional valence of the emotion component of the framework. Positive emotional response at the time of viewing the footage was associated with positive involuntary memories over the following week. The fourth study aimed to replicate and extend this finding, comparing the impact of engaging in two cognitive tasks after film viewing (equated for general load). Predictions were not supported and methodological considerations are discussed.
Results may have implications for understanding flashbacks and involuntary autobiographical memories occurring in everyday life and across psychological disorders. Further understanding of the proposed components of the clinical neuroscience framework may even help inform targeted treatments to prevent, or lessen, the formation and frequency of distressing involuntary memories.

Keywords: mental imagery
Posttraumatic stress disorder
intrusive memory
trauma film paradigm
neuroimaging
flashbacks
autobiographical memory
Advisor: Holmes, E
Mackay, C