This study aimed to investigate the psychophysiological correlates and the effectiveness of different dual-attention tasks used during eye movement desensitization and reprocessing (EMDR) (1)
“Abstract – Sixty-two non-clinical participants with negative autobiographical memories received a single session of EMDR without eye movements, or EMDR that included eye movements of either varied or fixed rate of speed. Subjective units of distress and vividness of the memory were recorded at pre-treatment, post-treatment, and 1 week follow-up. EMDR-with eye movements led to greater reduction in distress than EMDRwithout eye movements. Heart rate decreased significantly when eye movements began; skin conductance decreased during eye movement sets; heart rate variability and respiration rate increased significantly as eye movements continued; and orienting responses were more frequent in the eye movement than no-eye movement condition at the start of exposure. Findings indicate that the eye movement component in EMDR is beneficial, and is coupled with distinct psychophysiological changes that may aid in processing negative memories.
An extensive body of literature has demonstrated efficacy of eye movement desensitization and reprocessing (EMDR) for the treatment of posttraumatic stress disorder (PTSD). Meta-analyses that have examined efficacy of EMDR have concluded that it is as effective as traditional exposure therapy (Bisson et al., 2007; Bradley, Greene, Russ, Dutra, & Westen, 2005), and many international clinical practice guidelines recommend both therapies for the treatment of PTSD (Foa, Keane, Friedman, & Cohen, 2009; National Institute for Clinical Excellence, 2005). However, processes that operate in EMDR remain unclear…
EMDR is a complex therapy with many elements (Solomon & Shapiro, 2008). Processes identified in EMDR include mindfulness, somatic awareness, free association, cognitive restructuring, and conditioning. These processes may interact to create the positive effects achieved through EMDR (Gunter & Bodner, 2009; Solomon & Shapiro, 2008). However, the mechanism of change in EMDR that has received most attention in the scientific literature is the eye movements (EMs) and other bilateral stimulation (i.e., tones and tapping) that are used as a dual-attention task within the procedure.
It has been demonstrated that a single session of EMDR-with EMs leads to greater reductions in distress compared to EMDR-without EMs (Lee & Drummond, 2008; Wilson, Silver, Covi, & Foster, 1996).
… literature demonstrates that EMs have various effects on cognitive, neurological, and physiological processes that aid in memory processing. Laboratory research on non-clinical samples has demonstrated that when negative memories are recalled induced EMs decrease the emotionality and degree of vividness associated with them (Andrade, Kavanagh, & Baddeley, 1997; Barrowcliff, Gray, MacCulloch, Freeman, & MacCulloch, 2004; Gunter & Bodner, 2008; Kavanagh, Freese, Andrade, & May, 2001; Maxfield, Melnyk, & Hayman, 2008; van den Hout, Muris, Salemink, & Kindt, 2001).
Induced saccadic EMs have also been shown to affect cognitive processes such that they enhance episodic memory retrieval (Christman, Garvey, Propper, & Phaneuf, 2003; Christman, Propper, & Dion, 2004; Propper & Christman, 2008), increase the accuracy of memories recalled (Christman et al., 2004; Lyle, Logan, & Roediger, 2008; Parker, Relph, & Dagnall, 2008), induce cognitive and semantic flexibility, and facilitate attentional orienting (Kuiken, Bears, Miall, & Smith, 2001-2002). Research investigating the neurological effects of EMs has demonstrated that saccadic EMs create changes in brain activation that enhance memory processing (Christman et al., 2003; 2004; Christman, Propper, & Brown, 2006).
EMs produce distinct psychophysiological effects, with most studies suggesting that they are associated with psychophysiological dearousal (for a review, see Söndergaard & Elofsson, 2008). For example, Barrowcliff et al. (2004) found that when participants brought-to-mind negative autobiographical memories EMs, compared to an eyes stationary condition, consistently reduced physiological arousal as indicated by significantly lower skin conductance. They concluded that their findings offer support for the orienting response theory of EMDR (McCulloch & Feldman, 1996).
The orienting response (OR) was first described by Pavlov (1927) as “a “what-is-it” reflex which brings about the immediate response in man and animals to the slightest change in the world around them, so that they immediately orientate their appropriate receptor organ in accordance with the perceptible quality in the agent bringing about the change, making full investigation of it” (p. 12). Russian physiologist Eugene Sokolov (1963) proposed that the OR has two distinct phases: first, an alerting reaction in response to a novel stimulus in the environment; and second, habituation that leads to a reduction of the OR with repeated stimulus presentations in the face of no danger or threat. The OR is a well defined reflex and it is one of the most heavily investigated topics in psychophysiology (Sokolov & Cacioppo, 1997). The psychophysiological profile of the OR is characterized by an increase in parasympathetic tone (reflected by bradycardia and increased heart rate variability), decreases in respiration rate, and an increase in sympathetic tone (reflected by skin conductance increases and skin temperature reductions) (Öhman, Hamm, & Hugdahl, 2000). This reaction is a short-term (less than 10 seconds) response that habituates quickly.
Shapiro (1995) has proposed that desensitization of trauma memories occurs in EMDR through possible mechanisms such as the orienting response, and other mechanisms such disruptions in working memory and reciprocal inhibition.
The EM component in EMDR is thought to aid in the processing of memories by taxing working memory (Maxfield et al., 2008). Working memory theories of EMDR are based on Baddeley and Hitch’s (1974) model that states that working memory is a capacity limited system that is responsible for consciously maintaining information in the face of ongoing information processing and/or distraction. Working memory theory proposes that targeted memories are held in working memory during EMDR. Concurrently engaging in EMs during EMDR overloads working memory capacity and, in turn, the memories held in mind become less vivid. Working memory theory predicts that the more complex the dual-attention task in EMDR, the greater the reductions in vividness and distress associated with negative memories
A third account of EMDR proposes that counter-conditioning through reciprocal inhibition (Wolpe, 1991) is a mechanism underlying EMDR. The theory of reciprocal inhibition posits that two incongruent responses (relaxation and anxiety) cannot coexist. Research suggests that the EMs in EMDR, through inducing ORs that dissipate, create a state of physiological dearousal while patients simultaneously think about the traumatic memory (Wilson et al., 1996). Thus, a relaxation response is paired with the distress associated with the traumatic memory and, in turn, the association between the traumatic memory and the distress response weakens. Studies using EMDR have found that psychophysiological dearousal occurs from before to after successful treatment (Aubert-Khalfa, Roques, Blin, 2008; Forbes, Creamer & Rycroft, 1994; Sack, Lempa, & Lamprecht, 2007). Surprisingly, however, very little empirical research has examined psychophysiological changes during treatment sessions in patients with PTSD.
The first published study to have examined the mechanisms of EMDR by investigating the autonomic responses during EMDR was by Wilson et al. (1996). Eighteen subjects with distressing memories of traumatic events were treated with a single session of either EMDRwith EMs or two comparison treatments (EMDR-with tapping, or EMDR-with no EMs). EMDR-with EMs, but neither of the comparison conditions, led to significant physiological dearousal from before to after treatment. Onset of the EMs was associated with a relaxation response, suggesting that reciprocal inhibition is at least one of the mechanisms underlying EMDR.
More recently similar autonomic changes have been reported during EMDR intervention in naturalistic treatment settings with PTSD clients (Elofsson et al., 2008; Sack et al., 2008). Both studies provide support for a dearousal model of EMDR, as the authors demonstrated that EMDR resulted in significant physiological dearousal across the treatment session, reflected by a shift in autonomic balance as indicated by lowered heart rate (HR), respiration rate (RR), skin conductance (SC), and increased heart rate variability (HRV). Analysis of the within session physiological processes also indicated that the EM component in EMDR was associated with certain physiological changes… HR significantly decreased within the first 10 seconds, and HRV increased, together indicating decreased sympathetic and increased parasympathetic activity respectively.
Findings to follow…
- Schubert, S.J., Lee, C.W. and Drummond, P.D. (2011) The efficacy and psychophysiological correlates of dual-attention tasks in eye movement desensitization and reprocessing (EMDR). Journal of Anxiety Disorders, 25 (1). pp. 1-11..
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