Amygdala intercalated neurons are required for expression of fear extinction

Tripping the 'fear switch' For many animals, an ability to switch from a 'normal' bold or exploratory approach to a situation to a more defensive approach when prudent is an important survival aid. Much is known about the role of entire brain areas in such processes, but what happens at the level of neuronal circuits is less well understood. 'Fear extinction' and 'renewal', two processes in which learned fearful responses to stimuli associated with unpleasant consequences are unlearned, then renewed, are effective models for probing mechanisms associated with changes in behavioural state. Herry et al. show that changes in the balance of activity of two distinct neuronal populations in the basolateral amygdala can trigger transitions between states of high and low fear in mice. Likhtik et al. report another mechanism for 'unlearning' fearful memories, this time in rats. Amygdala cells known as intercalated neurons, which receive information from the basolateral amygdala, appear to be responsible in this case. This work suggests possible new avenues for the treatment of anxiety disorders.