The Neurocircuitry Underlying Additive Effects of Safety Instruction on Extinction Learning

Social support and fear-inhibition: an examination of underlying neural mechanisms

Recent work has demonstrated that reminders of those we are closest to have a unique combination of effects on fear learning and represent a new category of fear inhibitors, termed prepared fear suppressors. Notably, social-support-figure images have been shown to resist becoming associated with fear, suppress conditional-fear-responding and lead to long-term fear reduction. Due to the novelty of this category, understanding the underlying neural mechanisms that support these unique abilities of social-support-reminders has yet to be investigated. Here, we examined the neural correlates that enable social-support-reminders to resist becoming associated with fear during a retardation-of-acquisition test. We found that social-support-figure-images (vs stranger-images) were less readily associated with fear, replicating prior work, and that this effect was associated with decreased amygdala activity and increased ventromedial prefrontal cortex (VMPFC) activity for social-support-figure-images (vs stranger-images), suggesting that social-support-engagement of the VMPFC and consequent inhibition of the amygdala may contribute to unique their inhibitory effects. Connectivity analyses supported this interpretation, showing greater connectivity between the VMPFC and left amygdala for social-support-figure-images (vs stranger-images).

Neurocircuitry of Contingency Awareness in Pavlovian Fear Conditioning

In Pavlovian fear conditioning, contingency awareness provides an indicator of explicit fear learning. A less studied aspect of fear-based psychopathologies and their treatment, awareness of learned fear is a common cause of distress in persons with such conditions and is a focus of their treatment. The present work is a substudy of a broader fear-conditioning fMRI study. Following fear conditioning, we identified a subset of individuals who did not exhibit explicit awareness of the CS-US contingency. This prompted an exploratory analysis of differences in "aware" versus "unaware" individuals after fear conditioning. Self-reported expectancies of the CS-US contingency obtained immediately following fear conditioning were used to differentiate the two groups. Results corrected for multiple comparisons indicated significantly greater BOLD signal in the bilateral dlPFC, right vmPFC, bilateral vlPFC, left insula, left hippocampus, and bilateral amygdala for the CS+>CS- contrast in the aware group compared with the unaware group (all p values ≤ 0.004). PPI analysis with a left hippocampal seed indicated stronger coupling with the dlPFC and vmPFC in the aware group compared with the unaware group (all p values ≤ 0.002). Our findings add to our current knowledge of the networks involved in explicit learning and awareness of conditioned fear, with important clinical implications.