Passive or subliminal re-exposure is sufficient for fear modulation in eye-movement intervention

Bilateral eye movement (EM) intervention-the core component of eye movement desensitization and reprocessing (EMDR) therapy-has been implemented as a dual-task procedure that requires active retrieval and maintenance of traumatic memories during concurrent eye movements. However, it remains unclear whether explicit memory retrieval is essential for its therapeutic efficacy. To address this question, participants first acquired conditioned fear to snake/spider images and then received either passive (Experiment 1: N = 56) or subliminal (Experiment 2: N = 83) re-exposure to eccentrically presented conditioned stimuli for memory reactivation. Smooth-pursuit EMs were performed during re-exposure as the intervention. Results showed that passive re-exposure significantly reduced skin conductance responses (SCRs) to fear-conditioned stimuli during the intervention and 24 h later. In contrast, subliminal re-exposure did not alter immediate physiological responses, but it produced sustained reductions in both the frequency and emotional intensity of intrusive thoughts about the conditioned stimuli over the subsequent week, relative to control conditions lacking either EM intervention or subliminal re-exposure. Notably, participants reported significantly lower emotional distress during the intervention under unconscious than conscious re-exposure. These findings advance our understanding of the mechanisms underlying EMDR and suggest a promising noninvasive strategy for mitigating traumatic emotional responses without requiring active or conscious engagement with distressing memories.