آیا این فقط یک حواس پرتی صرف است؟ وظایف کلامی نیمه آسیب زا می تواند فلش بک آنالوگ را افزایش دهد اما باعث کاهش عملکرد حافظه داوطلبانه می شود

Abstract Several experiments have shown that we can reduce the frequency of analogue flashbacks with competing tasks presented during a trauma film (i.e. peri-traumatically). A “distraction” hypothesis suggests that any competing task may reduce flashbacks due to distraction and/or a load on executive control. Alternatively, a “modality” hypothesis based on clinical models of PTSD suggests that certain tasks will not protect against intrusions (Experiment 1) and could actually increase them (Experiment 2). Experiment 1 contrasted two concurrent tasks, Verbal Interference (counting backwards in threes) and Visuospatial tapping, against a no-task Control condition during trauma film viewing. The Visuospatial group had significantly fewer intrusions of the film over 1-week than the Control group. Contrary to a distraction account, the Verbal Interference group did not show this effect. Using a larger sample, Experiment 2 showed that the Verbal Interference group (counting backwards in sevens) had more intrusions (and inferior voluntary memory) than no-task Controls. We propose that this is in line with a modality hypothesis concerning trauma flashbacks. Disrupting verbal/conceptual processing during trauma could be harmful for later flashbacks.

1. Introduction ‘Flashbacks’ are a hallmark symptom of post-traumatic distress disorder (PTSD; American Psychiatric Association, [APA], 1994). In PTSD, vivid, intrusive, negative images of excerpts from a traumatic event “pop” into consciousness, apparently spontaneously, causing distress. The encoding stage has been deemed critical for the subsequent occurrence of flashbacks (for a review see Brewin & Holmes, 2003). Both contemporary theories of PTSD and cognitive memory models conceptualise flashbacks and intrusive memories as reflecting instances of ‘faulty information processing’ at the time of the trauma i.e. peri-traumatically. Such models include Ehlers and Clark's (2000) cognitive theory of PTSD, dual representation theory (DRT; Brewin, 2001, Brewin, 2003 and Brewin et al., 1996), and Conway's model of autobiographical memory (Conway et al., 2004 and Conway and Pleydell-Pearce, 2000), see also Dalgleish (2004). Whilst these theories differ in other respects, in relation to intrusion formation they make similar predictions (see Holmes et al., 2004 and Holmes and Bourne, 2008): that is, extreme emotional responses at points in a traumatic event can cause a shift in processing style away from “conceptual” or “verbal” processing of events (focussing on the situation's meaning) towards more “data-driven”, “sensory-perceptual”, or “visuospatial” processing (focussing on sensory impressions). This peri-traumatic shift in processing style is theorized to cause those events encoded relatively more perceptually/visuospatially to become intrusive. The view we describe above leads to two interesting predictions, which we shall refer to as the “modality” hypotheses. First, peri-traumatic disruptions to conceptual/verbal processing should increase later flashbacks. Second, peri-traumatic disruptions to sensory/visuospatial processing should reduce later flashbacks. While there is now accumulating evidence for the latter prediction, evidence for the former is sparse. The experimental method used to investigate the impact of peri-traumatic processing on subsequent flashbacks is the trauma film paradigm (for a review see Holmes & Bourne, 2008). Healthy individuals are exposed to an event analogous to trauma, namely a film depicting stressful or traumatic events such as actual or threatened death or serious injury (PTSD Criterion A; APA, 1994). Any analogue flashbacks to the film (that is, intrusive image-based memories) are recorded in a diary. Participants sometimes find that verbal thoughts about the film may also intrude (Hagenaars, Brewin, van Minnen, Holmes, & Hoogduin, 2010). However our primary interest concerns intrusive images, as an analogue of the vivid, sensory nature of clinical flashbacks. It is the image-based memories in the diary that are analysed accordingly in this study, and referred to henceforth as intrusions. Predictions about impact on intrusion frequency can be tested by manipulating conditions at encoding, for example by using modality specific dual tasks. Several studies have shown that peri-traumatic visuospatial tasks reduce the frequency of later intrusions. Complex spatial key tapping was used in Holmes et al. (2004, Expts. 1 & 2) and Brewin and Saunders (2001), and clay modelling in Stuart, Holmes, and Brewin (2006). Moreover, such tasks have also been shown to be effective soon post-trauma (Holmes, James, Coode-Bate, & Deeprose, 2009). In contrast, only one study has shown that a peri-traumatic verbal-interference task can increase later intrusions. Holmes et al. (2004, Expt. 3) found that counting out-loud backwards in threes increased the number of intrusions relative to a no-task control group. However, Krans, Naring, and Becker (2009) found that a similar task decreased rather than increased intrusions. According to a general attention and memory approach, it is possible that any dual task at encoding will interfere with film processing and thereby simply reduce intrusions by distraction (see Gunter and Bodner, 2008 and Krans et al., 2009). This alternative account we shall refer to as the “distraction” hypothesis. It should be noted that Gunter and Bodner (2008) used a different experimental paradigm in which (non-clinical) participants were asked to recall unpleasant autobiographical memory concurrent to eye movements (see also: Andrade et al., 1997, Kavanagh et al., 2001 and van den Hout et al., 2001). Two visuospatial tasks (eye movements as well as a drawing task) and an auditory shadowing task led to reductions in vividness and emotionality. Gunter and Bodner suggested that any distractor task that taxes the central executive could produce benefits when simultaneously holding a memory in mind irrespective of the specific modality of the task. In contrast, results in PTSD patients indicated that modality may be important since concurrent eye movements reduced emotionality and vividness of recalled trauma images relative to no task whereas a verbal counting task did not (Lilley, Andrade, Turpin, Sabin-Farrell, & Holmes, 2009). In the current paper we are interested in the encoding rather than the recall stage, but a similar argument can be posited for distraction versus modality views (Baddeley and Andrade, 2000 and Kemps and Tiggemann, 2007). Other research appears relevant to this debate. A more perceptual encoding style predicted increased intrusions after a film relative to a more conceptual encoding style (Halligan, Clark, & Ehlers, 2002), with related results via a manipulation of these processing styles post-trauma (Kindt, van den Hout, Arntz, & Drost, 2008). A verbal distraction condition post-film (a semantic naming task which could be thought of as interrupting conceptual processing) led to more intrusions than concrete thinking (Ehring, Szeimies, & Schaffrick, 2009). Also, increased conceptual processing has been related to improved outcome in PTSD patients following therapy (Kindt, Buck, Arntz, & Soeter, 2007). However, studies are lacking which compare manipulations of both perceptual versus conceptual processing at encoding to test impact on later intrusions. Returning to trauma encoding, according to a “distraction hypothesis”, the modality of the peri-traumatic dual task would be irrelevant to its effect on intrusions. However, in contrast, our formulation of PTSD theories suggests that peri-traumatic tasks interfering specifically with sensory/visuospatial processing would selectively protect against later intrusions, whereas other tasks would not. We therefore sought to test, within the same experiment, whether a visuospatial, but not a non-visuospatial task, would reduce later intrusions of a trauma film. In a second study, we sought to test the stronger prediction that a verbal/conceptual interference task rather than being distracting would actually increase (not decrease) intrusions.