Title: Hippocampal Memory as a Limited Resource in an Uncertain World

Abstract: Neuroscience research has demonstrated that the hippocampus is critical for episodic memory and spatial learning, and recent work has led to widespread acceptance of the idea that the hippocampus systematically maps physical space and possibly any kind of state space. These kinds of theories, however, rest on the unrealistic assumption that human memory is somehow photographic. Episodic memory can sometimes be quite precise, it can sometimes be quite inaccurate, and it can sometimes be difficult to distinguish from imagination. To better understand the paradoxical nature of human memory, we have used functional magnetic resonance imaging, intracranial electroencephalography, and computational modeling to understand encoding and recall of stories, movies, and meaningful places encountered in virtual reality environments. Contrary to the current zeitgeist in neuroscience, our work converges with a long history of findings suggesting that the hippocampus does not comprehensively map human experience. Instead, neocortical networks appear to compositionally and schematically map the structure of events, actively maintaining a generative model that is used to support prediction and reconstructive memory. The hippocampus, in contrast, functions as a limited resource, rapidly caching salient or significant experiences and reinstating past experiences at critical moments. Rather than conceptualizing memory in terms of static maps or memory systems, episodic memory and navigation may dynamically emerge through temporally gated cortico-hippocampal interactions.