EMDR: eye movements superior to beeps in taxing working memory and reducing vividness of recollections.

Posttraumatic stress disorder (PTSD) is effectively treated with eye movement desensitization and reprocessing (EMDR) with patients making eye movements during recall of traumatic memories. Many therapists have replaced eye movements with bilateral beeps, but there are no data on the effects of beeps. Experimental studies suggest that eye movements may be beneficial because they tax working memory, especially the central executive component, but the presence/degree of taxation has not been assessed directly. Using discrimination Reaction Time (RT) tasks, we found that eye movements slow down RTs to auditive cues (experiment I), but binaural beeps do not slow down RTs to visual cues (experiment II). In an arguably more sensitive "Random Interval Repetition" task using tactile stimulation, working memory taxation of beeps and eye movements were directly compared. RTs slowed down during beeps, but the effects were much stronger for eye movements (experiment III). The same pattern was observed in a memory experiment with healthy volunteers (experiment IV): vividness of negative memories was reduced after both beeps and eye movements, but effects were larger for eye movements. Findings support a working memory account of EMDR and suggest that effects of beeps on negative memories are inferior to those of eye movements.