Invited essayA cognitive neuroscience account of posttraumatic stress disorder and its treatment
Section snippets
Features of PTSD requiring explanation
What distinguishes the type of response to trauma that we label as PTSD? Among the most interesting features of PTSD are the disorganization and incompleteness of the trauma memory, the reexperiencing of the traumatic event in the form of spontaneous “flashbacks”, the time distortion typical of flashbacks, the unpredictable time course of intrusive memories connected with the trauma, and the sense of unreality that typically surrounds the traumatic event. We also know that many effective
Dual representation theory
In order to explain these phenomena a cognitive theory based on multiple memory systems was proposed by Brewin et al. (1996). According to their dual representation theory, memories of a personally experienced traumatic event can be of two distinct types, stored in different representational formats. One type of format (“verbally accessible memory” or VAM) supports ordinary autobiographical memories that can be retrieved either automatically or using deliberate, strategic processes. VAM
Cognitive neuroscience and fear
Much of our understanding of the brain mechanisms involved in the response to extreme fear comes from studies of conditioning. One important set of findings concerns the durability of fear conditioning. Consistent with observations about the frequent return of fear after successful psychotherapy (Rachman, 1989), it has been found that fear responses in animals can be easily reinstated following successful extinction, for example by placing the animal into a different context (Bouton &
Cognitive neuroscience and memory
For the purposes of this article the distinction between declarative and nondeclarative, or explicit and implicit, forms of memory is important to bear in mind even though it does not map exactly onto clinical observations of PTSD. Declarative memory involves representations of facts and events that are subject to conscious recollection, verbal reflection, and explicit expression (Eichenbaum, 1997, Squire, 1994). A prime example is autobiographical memory. Declarative memory is supported by a
The effects of fear on memory
From the foregoing review it may be inferred that the hippocampal processing of information about fear-evoking situations results in the laying down of integrated, coherent representations of conscious experience, located in the appropriate temporal and spatial context. These representations are available for deliberate recall. However, it is possible for information to reach the amygdala via a number of different routes, independently of the hippocampus. For example, the visual areas of the
The normal response to trauma
Having reviewed the relevant cognitive science findings, we are now in a position to amplify dual representation theory and put forward a more detailed model of the response to trauma. Consistent with proposals by several authors including Metcalfe and Jacobs (1998), Pitman et al. (2000) and van der Kolk (1996), a key component is the relative functioning of the amygdala and hippocampus. Owing to the stress-induced release of glucocorticoids and their effects on the hippocampus, verbally
What goes wrong in PTSD?
In the foregoing account a successful trauma response was related to the creation of detailed VAM representations that were fully integrated with pre-existing knowledge structures. Creating detailed VAMs can occur either during the trauma or afterwards, through deliberate focusing on flashback content and repeated conscious processing of detailed information about the trauma. The corollary is that failure to create these representations will result in a considerable amount of trauma information
Psychological treatment of PTSD
Standard treatment directed at PTSD symptoms generally involves two elements, which may be used separately or together: The detailed and repeated exposure to traumatic information, and the modification of maladaptive beliefs about events, behaviours or symptoms. Both exposure and cognitive methods have been demonstrated to be effective (Foa & Meadows, 1997). In accounting for the success of prolonged exposure, Foa and Rothbaum (1998) proposed that erroneous information in the trauma memory is
Conclusion
The study of trauma reveals many complex processes that are poorly understood. One of the most fascinating concerns the paradoxical nature of trauma memories, which may be vague or vivid, intrusive or quiescent, under or out of control, and experienced in the present or the past. There is now a large amount of converging evidence from clinical observation, neuroanatomy, and cognitive science to suggest that the many facets of trauma recall reflect the operation of two independent types of
Acknowledgments
I am very grateful for the comments of Bernice Andrews, Lucy Berliner, Anke Ehlers, Ann Hackmann, Allison Harvey, Mike Kopelman, John Morton and Mick Rugg on the ideas presented in this article.
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