Representations of stimulus features in the ventral hippocampus.

Discriminating and categorizing the meaning of environmental stimuli and responding accordingly are essential for survival. The ventral hippocampus (vHPC) controls emotional and motivated behaviors in response to environmental cues and is hypothesized to do so in part by deciphering the positive or negative quality of these cues. Yet, what features of the environment are represented in the activity patterns of ventral CA1 (vCA1) neurons and whether the positive or negative meaning of stimuli is present at this stage remain unclear. Here, using two-photon calcium imaging across six experimental paradigms, we examined which features of salient stimuli are represented by vCA1 ensembles and found that identity, sensory features, and intensity-but not valence-are robustly encoded. These results offer a reappraisal of the vCA1 function, wherein information corresponding to individual stimulus features, and not their meaning, predominates. This organizational scheme may support flexible updating of stimulus value as internal states and environmental demands change.