Unifying spatial and episodic representations in the hippocampus through flexible memory use

A key question in neuroscience is why the hippocampus is essential for episodic memory in humans, while dominantly exhibiting spatial representations in a number of other species. Some accounts suggest that spatial representation is the primary hippocampal function. Here, we propose that the primary function is storing and retrieving episodic memories, and spatial representations emerge due to this memory function. To demonstrate this, we adopt a computational model that autonomously learns to store information in memory and retrieve it to solve a variety of tasks. In memory tasks, the model develops associations and categorical representations akin to concept cells. In navigation tasks, the model forms representations of the spatial structure, performs geometric computations, and even learns representations of unique events similar to recently discovered barcodes. Our model predicts that the hippocampus represents any task-relevant variable, if the animal learns the task, suggesting that space is not special for the hippocampus.