Surviving threats: neural circuit and computational implications of a new taxonomy of defensive behaviour

Animals exhibit a variety of different responses to threatening stimuli, including both innate and instrumental behaviours. LeDoux and Daw describe a new taxonomy of defensive behaviours and review what we know about the underlying neural circuits and computational processes. Research on defensive behaviour in mammals has in recent years focused on elicited reactions; however, organisms also make active choices when responding to danger. We propose a hierarchical taxonomy of defensive behaviour on the basis of known psychological processes. Included are three categories of reactions (reflexes, fixed reactions and habits) and three categories of goal-directed actions (direct action–outcome behaviours and actions based on implicit or explicit forecasting of outcomes). We then use this taxonomy to guide a summary of findings regarding the underlying neural circuits.