Habituation of anxiety and cortical hypervigilance during image-based exposure

Habituation (decreased response to stimuli with repeated exposure) of attentional hypervigilance (preferential allocation of attention to feared stimuli) was investigated in specific fear. Participants with high (n=13) or low (n=13) spider fear passively viewed bird (neutral) images and progressively 'scarier' spider (fear-relevant) and snake (negative) images, in separate six-stage hierarchies. Stage six contained the image from Stage one repeated. Electrophysiological (EEG) activity was recorded throughout and the P1 event-related potential (ERP) was taken as a cortical measure of attentional hypervigilance. Participants rated their subjective anxiety (Subjective Units of Distress Scale; SUDS) at four timepoints for each stage (0, 30, 60, 90 seconds). Both groups showed reductions in P1 amplitude at Stage 3 compared to Stage 1 in the spider image hierarchy, and compared to Stages 1 and 2 in the snake image hierarchy. Both groups also demonstrated re-emergence of P1 amplitude at Stage 6 compared to Stage 3 of the spider and snake hierarchies. High but not low spider fear participants showed habituation of subjective anxiety within later spider image stages (4-6), but there was little evidence of habituation between stages. Together, findings do not provide evidence for a fear-specific neural mechanism during image-based exposure. Findings may otherwise reflect covert avoidance of, or dishabituation of visual attention towards, evolutionary threat images. It difficult to determine if participants attended to images given the use of a passive viewing paradigm and the graded task may have confounded arousal with habituation. Future research may employ eye-tracking technology and non-graded stimuli.