Current State of the Neuroscience of Fear Extinction and Its Relevance to Anxiety Disorders.

The elucidation of the functional neuroanatomy of human fear, or threat, extinction has started in the 2000s by a series of enthusiastically greeted functional magnetic resonance imaging (fMRI) studies that were able to translate findings from rodent research about an involvement of the ventromedial prefrontal cortex (vmPFC) and the hippocampus in fear extinction into human models. Enthusiasm has been painfully dampened by a meta-analysis of human fMRI studies by Fullana and colleagues in 2018 who showed that activation in these areas is inconsistent, sending shock waves through the extinction research community. The present review guides readers from the field (as well as non-specialist readers desiring safe knowledge about human extinction mechanisms) during a series of exposures with corrective information. New information about extinction-related brain activation not considered by Fullana et al. will also be presented. After completion of this exposure-based fear reduction program, readers will trust that the reward learning system, the cerebellum, the vmPFC, the hippocampus, and a wider brain network are involved in human fear extinction, along with the neurotransmitters dopamine and noradrenaline. Specific elements of our exposure program include exploitation of the temporal dynamics of extinction, of the spatial heterogeneity of extinction-related brain activation, of functional connectivity methods, and of large sample sizes. Implications of insights from studies in healthy humans for the understanding and treatment of anxiety-related disorders are discussed.