Cued fear conditioning in humans using immersive Virtual Reality

Virtual Reality (VR) is a promising tool for the study of cued fear conditioning in humans because it allows the use of complex and realistic experimental situations. The present study aims to validate a task for the acquisition and extinction of cued fear learning through VR with ecologically relevant Unconditional Stimuli (USs). In a first experiment (n = 69), we evaluated the effectiveness of six USs specially created to be presented in a virtual environment and to provoke physiological and affective reactions of fear. The two stimuli that evoked significantly higher than baseline electromyographic responses during three trials were then selected to be used as the USs in a second experiment. Experiment 2 (n = 51) aimed to determine if the previously selected US could generate a conditioned response (CR) when associated with another visual stimulus (Conditioned Stimulus; CS) in a differential conditioning paradigm, and subsequently go through extinction. We measured physiological, subjective and behavioral responses of fear, and evaluated their relationship to trait anxiety. This study showed that visual CSs in a VR environment can potentiate a startle reflex during acquisition, but we observed no discrimination between stimuli that signaled the US (fear cues CS+) and stimuli that signaled the absence of the US (safety cue CS-). Nevertheless, differential learning was observed in subjective measures (US expectancy and retrospective anxiety ratings) during acquisition, where participants responded differently to fear and safety cues. Subjective CRs, but not physiological, were reduced during extinction. No changes were observed in response suppression presented with CS, and no relationship was found between trait anxiety and fear responses. We conclude that VR is an appropriate model to elicit valid unconditioned fear responses (URs). The results of the present experiments are particularly important given that subjective CRs (observed in Experiment 2) account for an important part of the clinical experience of anxiety-related disorders, which may help to translate the use of VR to exposure therapy. Future research could improve the task to effectively generate differential physiological and behavioral responses with greater sensitivity to individual differences.