Re: differential mechanism/ SUDS/ eye movements

Hi Shawn. Continuing with regard to the studies by Kavanaugh et al. (2001) and van den Hout et al. (2001) who found that eye movements decreased the vividness of, and affect related to autobiographical memories.

These were nonclinical studies that looked at EMs and imagery, and other task controls, in isolation. The findings were found to relate to images of experienced events, and not to laboratory pictures (Andrade et al. 1997). Andrade and Kavanaugh hypothesized that eye movements reduce image vividness, leading to reduced affect ; van den Hout hypothesized that eye movements reduce affect intensity which then leads to decreased vividness. Imagery/exposure showed a trend in increasing affect and vividness.

You describe a study by Malloy and Levis (citation please). This study seems to differ from the four component action studies of Andrade; Kavanaugh; Sharpley; and van den Hout -- these were not clinical analogue studies; they looked specifically at the effects of brief dual tasks. According to your description, Malloy and Levis conducted a study with snake images for students who were mildly snake phobic. Apparently as fear declined, image vividness increased. You stated that the researchers thought that low image vividness was an avoidance response, and that as fear decreased, avoidance decreased, and there was an increase in image clarity. You also point out that the study was not able to control for simple effects of practice on image clarity, and suggest another possibility -- imagery may have become more vivid because of practice and the relationship with fear reduction just an accidental correlation.

Actually I think the results of this clinical analogue study might be predictable: imagery improving with practice, and exposure decreasing fear. Perhaps we generally see these types of results with exposure therapy: more rich images, and less fear. Perhaps after EMDR the images are less vivid, but there is also less fear. There are a number of interesting related questions: What is the role of imagery in trauma therapy? How does imagery relate to information processing, memory, dissociation, and affect? Is there an optimal level of image vividness? And, what is the role of affect during the treatment process? How does affect relate to information processing, memory, dissociation, and imagery? Is there an optimal level of in session affect? Lots of interesting research topics ...

You wrote: “I'm still not firmly convinced the effect of eye movements is a substantial effect in explaining the efficacy of EMDR.” I would agree that there is to date no compelling evidence for the role of EMs in clinical dismantling studies. But that’s because there is still not one methodologically rigorous study that has investigated the differential effect of EMs in the treatment of civilian PTSD with an adequate sample. We really don’t know yet if the non-EM conditions have an effect equivalent to, greater than, or less than EMs, because the studies have been poorly conducted.

You wrote: “Your interpretation of how the Andrade/Kavanaugh mechanism may play itself out, if I'm understanding you correctly, boils down to one of titrating stimulus exposure.” This is their interpretation, not mine -- I’m wondering how to test the purported mechanism of action. I'd like to investigate if, and how, titration might enhance information processing.

You suggest that if the mechanism is titration, then there are CBT techniques that can be used to achieve the same type of effect. Have these CBT techniques been tested in PTSD? I am not aware of studies investigating the effect of titration, the efficacy of the specific procedures, or the impact of titration on PTSD outcome. If such studies exist, I’d appreciate citations, thanks. If not, I’m not sure what evidence you have that these may be superior to EMDR, which is a tested approach.

You wrote: “If you believe the actual mechanism of eye movements is to titrate the memory, shouldn't this be the explanation you offer your patients, rather than the standard EMDR explanation that it somehow physiologically triggers the adaptive processing mechanism? It seems disingenuous to believe the procedure works through one mechanism while telling the patient it works through a different mechanism.” Oh dear, why would you assume that EMDR clinicians do not provide good informed consent? What is difficult about telling clients that we don’t yet know why EMDR works?

You also say: “why not offer the patient a range of choices rather than imposing eye movements as the first tier and only going to others if problems with the eye movements arise?” It sounds like you are assuming that clinicians using EMDR don’t provide treatment choices, and that they impose EMDR. I hope that I am misinterpreting your post because its disturbing to think that you could make such assumptions. I can't understand why it would seem like this to you, as I doubt that such behaviors are common practice.

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