REPRESENTATION OF FEAR MEMORY FEATURES IN THE VENTRAL HIPPOCAMPUS

Memories are often comprised of a multitude of different associations of emotional and motivational information that are bound across space and time. Specific aspects of memories have been extensively researched, such as spatial or time representations in the hippocampus, but how the brain disentangles and again reconnects different features to represent a unified experience remains unclear. A key brain area where different information is thought to become integrated into memory representations is the CA1 hippocampus. In particular the ventral CA1 hippocampus (vCA1) has been identified to be involved in processing emotional information. In our study we use a virtual reality setup for mice to create fear memories during virtual spatial navigation. During the testing of the fear memories we were able to disentangle spatial, temporal and emotional behaviors and record the underlying neural representations in vCA1. We found that the fear association lead to discriminative behavior and distinct spatial representations of the fear context. Cue-related memories were characterized by a mixture of discriminative and generalizing behaviors which were also reflected in the vCA1 activity. While different neural populations encoded the fear associated cue and a novel cue, temporal activity sequences related to the fear memory were preserved in population state space and also connected to the fear context. We suggest that the maintenance of neural geometry, possibly involving interneurons, could represent a principle mechanism of how some memory features are applied to new experiences.