Object and object-memory representations across the proximodistal axis of CA1

Episodic memory requires information about objects to be integrated into a spatial framework. Place cells in the hippocampus encode spatial representations of objects that could be generated through signaling from the entorhinal cortex. Projections from lateral (LEC) and medial entorhinal cortex (MEC) to the hippocampus terminate in distal and proximal CA1, respectively. We recorded place cells in distal and proximal CA1 as rats explored an environment that contained objects. Place cells in distal CA1 demonstrated higher measures of spatial tuning, stability, and closer proximity of place fields to objects. Furthermore, remapping to object displacement was modulated by place field proximity to objects in distal, but not proximal CA1. Finally, representations of previous object locations were closer to those locations in distal CA1 than proximal CA1. Our data suggest that in cue-rich environments, LEC inputs to the hippocampus support spatial representations with higher spatial tuning, closer proximity to objects, and greater stability than those receiving inputs from MEC. This is consistent with functional segregation in the entorhinal-hippocampal circuits underlying object-place memory.

Automated summary

Episodic memory relies on integrating object information into a spatial framework, with place cells in the hippocampus representing spatial aspects of objects through inputs from the entorhinal cortex. The study found that in cue-rich environments, inputs from the lateral entorhinal cortex (LEC) to the hippocampus led to higher spatial tuning, closer proximity to objects, and greater stability compared to inputs from the medial entorhinal cortex (MEC). In particular, place cells in distal CA1 demonstrated superior spatial tuning and stability, as well as modulated remapping based on proximity to objects.