How does EMDR work?
Hout, van den, M. & Engelhardt, I. (2012).
 Journal of Experimental Psychology, 3 (5), 724-738.

Abstract

Eye movement desensitisation and reprocessing (EMDR) is an effective treatment for alleviating trauma symptoms. Eye movements or other ‘dual tasks’ are necessary for this. Bilateral situation is not needed. It is important that the dual task taxes working memory.

History and effects of EMDR

Eye movement desensitisation (EMDR) is used to treat posttraumatic stress disorder. A crucial part of the producer involves the patient recalling traumatic memories while simultaneously making horizontal eye movements Increasingly, these eye movements have been replaced by other intermitted bilateral stimulation.

A model of EMDR

The procedure of EMDR involves: 1) Volunteers recall unpleasant memories for a few seconds. they rate those memories in terms of vividness and emotionality. 2) They recall those memories for a second, longer time, while making eye movements by visually tracking a white circle that moves from side to side on a computer screen. 3) After a break, the memory is recalled under the same conditions as the first time and is again rated in terms of vividness and emotionality.

Hypothesis 1: EMDR works by recalling aversive memories and eye movements do not contribute anything

Studies show that: eye movement matter, the effects cannot be explained by exposure alone.

Hypothesis 2: EMDR works by stimulating ‘Interhemispheric communication’

Research dismisses this hypothesis.

Hypothesis 3: EMDR works by taxing working memory during recall

When simultaneously do two tasks that each tax WM, the tasks compete for the limited capacity of working memory. During recall, a memory becomes ‘labile’, events during recall influence how the memory is restored and may be recalled in the future. The ‘recall + eye movements’ combination will lead to ‘imagination deflation’.

Other tasks

An implication of the working memory theory is that not only eye movements, but any task should attenuate the vividness and hence the emotional tone of the memory. This has been found.  

Positive memories

According to the working memory theory, all emotional memories should lose their vividness when working memory is taxed during recall.

Findings showed that making eye movements during activation of positive thoughts rendered these thoughts less vivid and less positive.

Prospective memory and flash-forwards

Therapist have begun to use EMDR to treat a wide range of disorders. They assume that for many patients psychological complaints have been caused or intensified by an unpleasant event, and this event becomes the focus of EMDR sessions.

The working memory theory says that flash-forwards can be stripped of their impact in the same way as flashbacks. Research supports this theory.

How do we know if and how much working memory is taxed?

A traditional method for determining whether and how much cognitive capacity a mental task requires is the reaction time (RT) task. Task A is administered, where the participant responds as quickly as possible to a probe, and the RT is measured Task B is added to A. The degree to which the RT to task A slows down produces an index of the amount of cognitive capacity required by B.

Research shows that EMDR taxes working memory.

Low working memory capacity? Benefits from EMDR

There are individual differences in working memory capacity in general. For individuals who have a stronger delay during RT task when they make eye movements, eye movements have a large impact. The working memory theory suggests that, because of this big impact, people with low working memory capacity should benefit a lot from making eye movements.

Inverted U

The working memory theory states that the competition between recall and the distracting task leads to a decrease in vividness and emotionality. For this to happen, there needs to be a minimum degree of taxing. If this taxing exceeds a certain level there will be too little room for recall. This would mean that the link between working memory and the memory-effects has the form of an inverted U, too little and too much taxing both have little or no effect.

The effect of beeps

Theories about how a procedure works influences how the procedure is applied.

According to the working memory theory, little effects can be expected from ‘beeps’, as they are a passive task that may not even tax working memory.

Mindfulness and mindful breathing

Mindful breathing taxes working memory to the same extent as eye movements.