The role of consciousness in threat extinction learning

Extinction learning is regarded as a core mechanism underlying exposure therapy. The extent to which learned threats can be extinguished without conscious awareness is a controversial and on-going debate. We investigated whether implicit vs. explicit exposure to a threatened stimulus can modulate defence responses measured using pupillometry. Healthy participants underwent a threat conditioning paradigm in which one of the conditioned stimuli (CS) was perceptually suppressed using continuous flash suppression (CFS). Participants’ pupillary responses, CS pleasantness ratings, and trial-by-trial awareness of the CS were recorded. During Extinction, participants’ pupils dilated more in the trials in which they were unaware of the CS than in those in which they were aware of it (Cohen’s d = 0.57). After reinstatement, the percentage of fear recovery was greater for the CFS-suppressed CS than the CS with full awareness. The current study suggests that the modulation of fear responses by extinction with reduced visual awareness is weaker compared to extinction with full perceptual awareness.