Hippocampal reactivation of planned trajectories is required for effective goal choice in an allocentric memory task

It still remains unclear how the brain replays stored neural information, and whether such replay merely reflects past experiences or also plans of future endeavours. Hippocampal activity provides a representation of the world around us and our movement and navigation within that world, but it is not known if and to what extent the chosen navigational reference frame can influence hippocampal representations during memory-based tasks, including those focused on future activity. Here, we develop and employ two naturalistic, carefully controlled variants of the everyday memory task to model the use of egocentric and allocentric coordinates in the same arena. By recording hippocampal neural activity through miniature microscopes in rats performing each of the two tasks, we uncover differences in the representation of space, and in the features of memory-based action planning. By also deploying optogenetic inactivation during navigational decision making, we find that hippocampal representations observed during the planning phase are necessary for solving the allocentric, but not the egocentric version of the task. Overall, our findings reveal a functional link between non-local hippocampal representations and allocentric navigation.