Disentangling eye movement desensitization and reprocessing mechanisms of action: The impact of eye movements in the eye blink conditioning task.

Objectives: Eye movement desensitization and reprocessing (EMDR) is an effective evidence-based treatment for post-traumatic stress disorder. However, the therapeutic mechanisms underlying eye movements (EM) remain unclear. This study aimed to investigate the effect of horizontal EM on fear extinction learning in healthy individuals, using an Eye Blink Conditioning (EBC) task. This experimental paradigm has been widely used to explore associative fear learning and memory as a form of classical conditioning.

Methods: Healthy participants were included to the study protocol and divided randomly into two groups. The EM group (n = 20) were asked to follow horizontally the experimenter's moving finger at the beginning of the extinction phase and the control group (n = 19) did not engage in any specific task. Sociodemographic and clinical information was collected. Percentage of conditioned response (CR) occurrence, time of onset and intensity between and within groups over longitudinal time were analysed using generalized multilevel mixed effects for repeated measures.

Results: Results showed accelerated extinction learning in the EM group, with an 18.2% probability of CR occurrence in the first block of extinction, compared to the control group (40.9%) (p-value = .007).

Conclusions: The findings indicate that horizontal EM accelerates the extinction process in the EBC task. Therefore, this paradigm, used for studying associative learning and memory, could serve as an objective measure to investigate the mechanisms of action involved in desensitizing traumatic experiences during EMDR treatment.