Multimodal evidence for delayed fear extinction in adolescence and young adulthood.

Previous research in rodents and humans points to an evolutionarily conserved profile of blunted fear extinction during adolescence, underpinned by brain structures such as the amygdala and medial prefrontal cortex (mPFC). In this study, we examine age-related effects on the function and structural connectivity of this system in fear extinction in adolescence and young adulthood. Younger age was associated with greater amygdala activity and delayed mPFC engagement to learned threat cues as compared to safety cues. Furthermore, greater structural integrity of the uncinate fasciculus, a white matter tract that connects the amygdala and mPFC, mediated the relationship between age and acceleration of mPFC engagement during extinction. These findings suggest that age-related changes in the structure and function of amygdala-mPFC circuitry may underlie the protracted maturation of fear regulatory processes, rendering younger individuals more vulnerable to anxiety disorders, which emerge during development.