Re:Comments on Andrade et al., and Kavanagh et al.

You make an astute observation: There are many "theories" as to why eye movements, and other laterally alternating stimuli/dual attention, are a powerful component. Yet some of the ideas seem to contradict one another. The only two things these theories seem to have in common are (1) their alliance to the assumption that eye movements etc. are in fact an important part of the treatment and (2) a lack of evidence for the hypothesized role of eye movements.

The excpetion to this is the Andrade/Kavanagh group. They clearly have a theory about the disruptive effect of eye movements on processing in the visual-spatial sketchpad, and thus far their data support their hypotheses. However, what is missing a link between the effects of eye movements on imagery while the imagery is occurring, and how this translates into symptom reduction in the real world when people confront trauma reminders.

Sandra has repeatedly used the term "titration" to describe the role of eye movements. I understand this to mean that eye movements help patients reduce the distress of the image, presumably allowing them to stay with the image and associated thoughts/feelings rather than avoid it. Sandra, please correct me if I've misrepresented this. A titration function could easily be consistent with the Andrade/Kavanagh model. But "titration" in my mind implies that eye movements simply help to regulate the dose of exposure, but the "active ingredient" per se is still exposure to the trauma memory in the absence of harmful consequences. The advantage of the titration hypothesis is that we can generate hypotheses as to other ways in which titration could occur (e.g., creating a hierarchy of feared images that differ in level of detail, recalling the memory with eyes open vs. eyes closed, using the past tense rather than the present tenses, imagining the scene as if it is in the distance rather that as if it is happening right now, etc.). Theoretically, these strategies could all serve the same function. They could be tested to see if any of them are more or less effective, and to see if any are more or less accepted by patients.

Shapiro has been all over the map with regard to speculation about eye movements. In 1991, she offered five different hypotheses: "The apparent effect of the saccadic and tracking eye movements may involve the: (1) disruption of the complex of habitual physiological responses elicited by the traumatic memory (distortion of response stereotypy), (2) distraction value of the movements, (3) induction of a profound trance state (analogous to hypnogognic sleep state) in which the client accepts self-induced suggestions, (4) interference with the trace memory caused by neuronal bursts which typify eye-movement...and (5)neurophysiological aspects of eye movement effects such as REM-induced muscular inhibition by way of the reticular formation, parasympathetic involvement, or effect on cortical neural functions." (p. 134).

In the first edition of her book, Shapiro suggests the following rationale for eye movements: "The eye movements we use in EMDR seem to unlock the nervous system and allow your brain to process the experience. That may be what is happening in REM, or dream, sleep: The eye movements may be involved in processing the unconscious material." (p. 121)

Later in the book, she speculates that, based on animal findings that "have indicated that repetitive low-voltage currents change the synaptic potential that are directly related to memory processing" and that "eye movements may be essentially equivalent to a low-voltage current and therefore responsible for the same synaptic changes" (p. 315, 315-316).

Welch & Beere (2002), suggest that "EMDR, by stimulating both hemispheres, could possibly promote an integration of hemispheric functioning as well as normalization of brain activation patterns." (p. 171)

Others (I can't provide the citation off hand) think that eye movements will activate an orienting response that somehow improves processing the memory. And there are lots more theories.

Yet, there is precious little data to even support the idea that eye movements improve outcome, much less function in any particular way, with the exception of diminishing image intensity and possibly emotional intensity while engaging in imagery ala Andrade and Kavanagh.

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Re:Comments on Andrade et al., and Kavanagh et al., by client, 11/07/02

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