The effect of emotional context on cognitive inhibition and attentional processing in dissociative identity disorder
Introduction
Being broadly characterised as breakdowns in integrated psychobiological processing and operating (American Psychiatric Association, 2000; Nijenhuis, van der Hart, & Steele, 2002), episodes of dissociation (e.g., dissociative symptoms) would be expected to have an impact on executive functioning in working memory. Executive functions are involved in attention, coordination of cognitive systems, planning, volition and action (Baddeley, 1996; Lezak, 1995). A fundamental question is whether pathological dissociative symptoms, and those people with a dissociative disorder, display generalised and stable anomalies in executive functioning, or whether given the association between trauma and dissociative symptoms anomalous executive functioning is more state dependent, vacillating between typical and atypical functioning depending on variables such as emotional state or emotional context.
Previous work has shown a relationship between aspects of executive functioning in working memory and dissociation when tested with neutral (Freyd, Martorello, Alvarado, Hayes, & Christman, 1998) and emotional stimuli (e.g., DePrince & Freyd, 1999; Waller et al., 1995). This work has utilised an incongruent colour-word task (i.e., Stroop, 1935) and word naming tasks to examining interference and attentional bias in information processing in non-clinical dissociators. Initial findings showed evidence of general and stable deficits in executive functioning in high non-clinical dissociators in the form of greater Stroop processing interference (using traditional neutral Stroop stimuli) and more attentional bias (i.e., slower processing) to threat words. In a later study of Stroop interference it was revealed that high non-clinical dissociators displayed less interference compared to low dissociators when performing two simultaneous tasks (i.e., dividing attention), and thereby loading working memory (DePrince & Freyd, 1999). Together (see Freyd & DePrince, 2001, for review) these findings suggest that while dissociation may be related to executive deficits when tested under selective attention conditions, it is related to enhanced performance when tested under divided attention conditions. In short, interference effects in high and low non-clinical dissociators display state-like characteristics that are dependent on environmental demands.
Studies with dissociative identity disorder (DID) samples examining cognitive inhibition, an executive process involved in selective attention, have demonstrated differing performances using differing experimental stimuli. With reference to cognitive inhibition, Baddeley (1996) argues that “one important role of the central executive should be to act as an attentional controller, selecting certain streams of incoming information and rejecting others” (p. 8). In line with this function, cognitive inhibition refers to the ability to withhold the mental representations of distracting stimuli from attention so that target stimuli can be fully processed with only limited interference from competing information (Neill, 1977; Tipper, 1985). Cognitive inhibition is a central process in the ability to engage in selective attention. Johnson and Dark (1986, p. 44) describe selective attention as the “differential processing of simultaneous sources of information”. For differential processing of information at least two processes are required: the activation of relevant information and the inhibition of irrelevant information (Kane, May, Hasher, Rahhal, & Stoltzfus, 1997). In the laboratory cognitive inhibitory ability is often assessed via tasks of negative priming. Negative priming refers to the retardation in response time compared to baseline for a target stimulus presented as a distractor in the previous trial.
Using a negative priming task (the flanker task—see method for overview) to infer cognitive inhibitory ability, Dorahy, Irwin, and Middleton (2002, study 2) found no evidence of negative priming (i.e., weakened cognitive inhibition) in a sample of DID participants when words were used as experimental stimuli. However, in studies that used single digit numbers as test stimuli (Dorahy, Irwin, & Middleton, 2004; Dorahy, Middleton, & Irwin, in press), DID samples displayed significant negative priming (i.e., effective cognitive inhibition). Dorahy, Irwin, and Middleton (in press) suggest that word stimuli may create a more anxiety provoking experimental context than number stimuli because of the uncertainty surrounding the possible threatening quality of even emotionally neutral words for individuals with DID. The currently study was designed to directly address this issue by presenting participants with a single digit number negative priming task in two distinct emotional contexts. Single digit numbers were used in the negative priming task because, as mentioned above, DID samples have shown effective cognitive inhibition when using them. The emotional contexts were manipulated through specific experimental instructions and the use of neutral and emotionally charged negative words. In the first test session participants were told they would see neutral words and were presented with a single neutral word between a set of negative priming trials. In the second test session participants completed the same task but half the neutral stimuli were replaced with emotionally charged words and they were told that negative words would be presented. Along with the DID sample, a control sample and non-dissociative psychiatric sample were utilised to provide more experimental control. Given the theoretical and empirical link between reduced negative priming and both dissociation (Dorahy et al., 2002) and schizotypy (e.g., Beech & Claridge, 1987), these constructs were also assessed.
The study aimed to examine cognitive inhibitory ability in both a neutral and emotionally aversive experimental context. From the suggestive but inconclusive indications of previous studies, it was predicted that the DID sample would display significant negative priming (i.e., effective cognitive inhibition) in the neutral context, but no evidence of negative priming (i.e., weakened inhibition) in the negative context. In addition, following the results from Waller et al. (1995) in a non-clinical sample, it was expected that the DID group would display an attentional bias (i.e., slower response times) to negative words compared to neutral words.
Section snippets
Participants
The DID sample comprised 11 participants (10 females; 1 male) with an Axis I diagnosis of DID from both a psychiatrist and an independent structured clinical interview assessment (i.e., Dissociative Disorders Interview Schedule; Ross et al., 1989). Ten of the 11 participants had taken part in at least one other study of information processing conducted several months before. Participants were aged between 20 and 46 years of age (M=33.7 years, SD=9.1) and had been in treatment for DID from
Results
There were no significant differences between groups for age [F(2,30)=1.64] or days between testing [F(2,30)=.96]. In addition, the total daily dosage of psychotropic medication did not differ for the DID and psychiatric comparison samples [t(20)=.07]. A two-way mixed ANOVA (context by group) on anxiety scores showed no main effect for context [F(1,30)=.94] or group [F(2,30)=.07]. However, the interaction between context and group was significant [F(2,30)=6.84, p<.01]. Post-hoc analyses show
Discussion
It was predicted that cognitive inhibitory processes in DID would display state-like characteristics when tested under differing emotional contexts. More specifically, it was expected that a DID sample would display effective inhibitory performance in a neutral, non-threatening context, but when tested in an emotionally negative context inhibitory ability would weakened. Support for this hypothesis was found in the form of significant negative priming in the DID sample in the neutral context,
Acknowledgements
This work was completed while Martin Dorahy was at the School of Psychology, University of New England, Armidale, N.S.W., Australia. The authors would like to thank Dean Davidson for his help in computer programming and an anonymous reviewer for their comments on an earlier draft of this paper.
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