Habituation of self-reported anxiety and cortical hyper-vigilance during image-based exposure to spiders

Background and objectives: The aim of the study was to examine habituation of subjective anxiety and electrophysiological correlates of cortical hyper-vigilance during exposure to spider images among high (n = 12) and low (n = 11) spider fear groups.

Methods: Participants viewed a six-stage hierarchy of spider images. The images used at stage 1 and stage 6 were the same. Subjective anxiety was rated at four intervals during each three-minute exposure stage (0, 60, 120, and 180 s) and event-related potentials (ERPs) were averaged across these epochs (0-60, 60-120, 120-180).

Results: High spider fearfuls demonstrated greater habituation of self-reported anxiety within and between exposure stages compared to low fearfuls. Consistent with attentional hyper-vigilance, the high-fear group also demonstrated greater P1 amplitude in response to spider images. In both groups, habituation of P1 amplitude was found at later relative to earlier stages, but increased at stage six when the stage 1 image was re-presented, despite low subjective anxiety.

Limitations: While the passive viewing paradigm mirrored image-based exposure, it was not possible to determine whether participants engaged in avoidance strategies. In addition, further research is needed to assess the relevance of habituation and reinstatement of P1 amplitude to therapeutic outcome.

Conclusions: Habituation of subjective anxiety during image-based exposure is not necessarily accompanied by a reduction in measures of cortical hyper-vigilance. The reinstatement of the P1 response may indicate either re-activation of previous associations, less avoidance, or a more generalised dishabituation mechanism.