Brewin et al. (1996) have applied Brewin's (1989) dual representation theory (DRT) to post-traumatic stress reactions in general and to PTSD in particular. This approach endeavours to circumvent some of the difficulties of single-level theories discussed above by proposing two levels in memory at which trauma-related information can be represented. The first level of representation is of the individual's conscious experience of the traumatic event. This forms what Brewin et al. have called verbally accessible memories (VAMs), characterised by their ability to be deliberately retrieved and progressively edited by the traumatised individual. VAM representations, it is argued, as with Foa et al.'s fear network, comprise sensory, response, and meaning information centred on the traumatic event. The second level of representation proposed by Brewin et al. consists of what are called situational^ accessible memories (SAMs), containing information that cannot be deliberately accessed by the individual and that is not available for progressive editing in the same way as VAM information. In fact, SAMs, as the name suggests, are accessed only when aspects of the original traumatic situation cue their activation. DRT proposes that VAM and SAM representations are encoded in parallel at the time of the trauma and between them have the power to account for the range of PTSD phenomenology. For example, holistic, dissociative memories or "flashbacks" would be considered to be the result of the activation of SAM representations, whereas the person's ability to recount the trauma, for example in a therapeutic situation, would be a function of the accessibility of VAM representations. See Figure 6.10 for a schematic illustration of DRT.
Brewin et al. (1996) propose that successful emotional processing of VAM and SAM information related to the trauma may not always be possible. They suggest that in some circumstances, for example when the discrepancy between the trauma and prior assumptions is too great, emotional processing of trauma information will become chronic. Alternatively, emotional processing may be prematurely inhibited due to sustained efforts to avoid the reactivation of highly distressing information stored in VAM and SAM. In this situation, Brewin et al. suggest, there may be no active emotional processing, but the SAM information should still be accessible under certain circumstances and the individual is hence vulnerable to delayed-onset PTSD when those circumstances arise.
DRT offers a coherent account of the phenomenology of PTSD, and makes particularly clear statements concerning the more distinctive experiences such as flashbacks that traumatised individuals report. There is also considerable discussion of the various courses post-trauma, what Brewin et al. call the three endpoints of emotional processing, and the modi operandi of both cognitive and behaviour-based treatments are outlined in some detail. Finally, important processes such as attributions, social support, and attitudes to emotional expression are considered in tandem with the three endpoints of processing. One strength of Brewin et al.'s approach is the application of a coherent cognitive architecture which was developed as a general framework for understanding therapeutic processes (Brewin, 1989) to PTSD. It is
ENCODING IN VERBALLY ACCESSIBLE MEMORY (VAM)
INTRUSIVE MEMORIES AND EMOTIONS, SELECTIVE RECALL
CONTENTS OF AWARENESS
ENCODING IN SITUATIONALLY ACCESSIBLE MEMORY (SAM)
FLASHBACKS > DREAMS
Figure 6.10 A schematic illustration of dual representation theory a pplied to PTSD (based on Brewin et al., 1996).
perhaps too early to judge how much mileage the concepts of VAM and SAM will turn out to have, although Holmes, Brewin, and Hennessy (2004) have recently reported some interesting analogue-based support for the distinction. Some problems are immediately apparent; first, although credit is due to Brewin et al. for moving away from the single-level theories such as Foa et al.'s, VAMs and SAMs are still network-based representations, and the proposal of dual representations still leaves it unclear how higher-order models and assumptions about the world and the self might be represented (Dalgleish, 2004). Are these just one part of the VAM system? If so, then is it really true to say that the contents of such models are verbally accessible in their entirety? Furthermore, exactly how does the integration of information concerning the trauma into pre-existing VAM representations take place? And what functions do VAMs and SAMs serve in memory generally or are they merely systems for dealing with memory for emotional material? Overall, Brewin et al.'s ideas make considerable progress towards a coherent theory of mind which can account for the known variables of interest in PTSD; however, a number of important puzzles remain to be addressed.
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