A critical analysis of the Working Memory model of Eye Movement Desensitization and Reprocessing

Abstract

Eye Movement Desensitization and Reprocessing (EMDR) is one of the foremost interventions for posttraumatic stress disorder (PTSD). Treatment aims to desensitise and reprocess trauma memories by combining imaginal exposure to the trauma with concurrent bilateral stimulation, usually in the form of eye movements (EMs). Multiple explanations have been proposed to account for therapeutic effect of EMs in EMDR. This thesis examined a leading theoretical account: the working memory (WM) hypothesis.

To investigate the theory that EMs desensitise negative imagery in EMDR by taxing visuospatial WM, a series of experiments were conducted in which healthy subjects formed a visual image depicting a negative autobiographical memory while performing an EM task, an auditory task - designed to place similar demands on the central executive – and/or keeping both eyes stationary. We reliably found that EMs did not reduce image vividness and emotionality more than auditory interference. Evidence was mixed regarding the effect of EMs compared to fixation, although null-results may be explained by the use of a less powerful between-subjects design. These findings challenge the view that EMs interfere with distressing imagery in EMDR by taxing visuospatial WM, and are more consistent with the view that the general cognitive load of EMs can fully explain their desensitising effect on imagery in EMDR.

An important gap in current understanding of EMDR is how the WM interference created by EMs contributes to the reprocessing of trauma memories. A novel procedure was developed for use in laboratory settings to test the prediction that EMs facilitate memory reprocessing. In an initial study, healthy participants allowed their mind to wander between sets of negative recall with concurrent EMs, or fixation. Preliminary results showed that EMs did not facilitate mind wandering, although this may have reflected limitations in the study design. This novel procedure provides an avenue for future research on a revised model of how WM interference contribute to important processes in EMDR, beyond the immediate desensitisation of imagery.