Anxiety and Beyond: Diversity in Ventral Hippocampus Circuits and Function.

The ventral hippocampus (vHPC), initially implicated in anxiety regulation, is now recognized for its broader role in integrating emotional, motivational, and contextual information. This review synthesizes recent insights from rodent research presented at our 2025 Society for Neuroscience minisymposium, detailing how local inhibitory microcircuits, long-range projection-defined pathways, and neuromodulatory inputs interact to shape fear, anxiety, and reward behaviors. We emphasize how distinct circuits segregate fear and anxiety, resolve approach-avoidance conflicts, and integrate reward history. Serotonergic modulation, particularly from the median raphe, emerges as a critical regulator of vHPC dynamics, with pronounced sex-specific functional implications. Finally, we examine how vCA1 ensemble activity encodes emotionally salient stimuli and supports latent state inference, thereby enabling flexible decision-making under uncertainty. Collectively, these findings recast the vHPC as a modular, computationally rich structure essential for adaptive behavior, which may provide new insights into circuit-level dysfunction in affective disorders.