Anxiety disorders are thought to involve altered top-down regulation of the amygdala by the medial prefrontal cortex (mPFC), but the subset of neurons targeted have not been identified. Using various anatomical mapping methods, the authors showed that, in mice, there is a neuronal projection from the ventral mPFC (vmPFC) to the basomedial amygdala (BMA). Optogenetic activation of either vmPFC neurons or BMA neurons produced an anxiolytic effect in mouse models of anxiety, and the firing rates of BMA neurons differed between the anxiogenic and safe environment in these models. This revealed a vmPFC–BMA pathway involved in anxiety-like behaviours.