Fear extinction: from engrams to circuits
At the recent Federation of European Neuroscience Societies (FENS) meeting in Copenhagen, I chaired a session entitled “Fear extinction: from engrams to circuits”. In my talk, I reviewed what is known about the neural circuits responsible for extinction (or reduction) of learned fear associations that involve inhibition of the amygdala by the prefrontal cortex. A new approach is to study the extinction of active avoidance responses, which are excessive in anxiety disorders. Extinction of avoidance requires projections from the ventral hippocampus to the prefrontal cortex releasing the growth factor BDNF. Blocking BDNF production in hippocampal neurons with the CRISPR-Cas9 system impairs extinction. Clinical reduction of avoidance behaviors in patients would allow them to overcome their fears through fear extinction.