The ventral hippocampus: computations, circuits and functions.

Recent advances in systems neuroscience are revealing how mammalian limbic circuits integrate information about the external world with internal state to shape learning and guide behaviour. This process is especially important for affective and motivated behaviours, in which the meaning of external cues depends on both learned associations and the organism's current state. As a central hub within limbic networks, the ventral hippocampus (vHPC) integrates external and internal signals and routes them to circuits that regulate avoidance, reward seeking, social behaviour and stress responses. In this Review, we examine the behavioural roles, response properties and local and long-range circuitry of the rodent vHPC and consider how its computations are distributed across projection-defined neuronal subpopulations. We interpret these findings through the framework of an affective-motivational map, in which learning and ongoing physiological and affective states flexibly update what salient stimuli and contexts predict and how they are read out downstream. Different uses of this common representational architecture are proposed to underlie fear, reward seeking, feeding, social behaviour and stress, allowing the vHPC to support flexible behaviour across affective and motivational domains.