Robust Conjunctive Item–Place Coding by Hippocampal Neurons Parallels Learning What Happens Where

TLDR

The hippocampus is known to support memory for events within their context, yet direct evidence that hippocampal neurons encode event–context conjunctions remains lacking. We show that during learning, hippocampal neurons develop place‑specific responses to items that differ in meaning across contexts, with conjunctive coding emerging as enhanced item‑specific activity within a subset of the existing spatial map, supporting the role of hippocampal conjunctive representations in context‑specific memory acquisition.

Abstract

Previous research indicates a critical role of the hippocampus in memory for events in the context in which they occur. However, studies to date have not provided compelling evidence that hippocampal neurons encode event–context conjunctions directly associated with this kind of learning. Here we report that, as animals learn different meanings for items in distinct contexts, individual hippocampal neurons develop responses to specific stimuli in the places where they have differential significance. Furthermore, this conjunctive coding evolves in the form of enhanced item-specific responses within a subset of the preexisting spatial representation. These findings support the view that conjunctive representations in the hippocampus underlie the acquisition of context-specific memories.