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Authors & Affiliations
Elena Faillace, Francesco Gobbo, Rufus Mitchell-Heggs, Adrian J. Duskiewicz, Patrick Spooner, Richard G.M. Morris, Simon R. Schultz
Abstract
A major challenge in studying spatial memory is understanding whether and how different navigational strategies influence hippocampal spatial representations of the environment.We designed a spatial recency memory task with two variants: one requiring allocentric representations of location, the other entailing egocentric representations. 10 freely-moving rats were trained over 34 daily sessions; each day, rats learned and then recalled the position of a food reward among six locations. Each trial, animals entered the arena from one of four start locations, generating distinct origin-goal trajectory combinations. CA1 neurons expressing GCaMP6f were recorded with miniature microscopes (~195 cells/animal) during 7 consecutive sessions at asymptotic performance.We compared calcium activity patterns between pairs of trajectories with the same origin-goal, finding increased neural correlation among trajectories closer in space, confirming hippocampus’s role in spatial selectivity. To measure neural correlations, we aligned neural manifolds with canonical correlation analysis (CCA), enabling comparison of recordings in different neural spaces. Notably, trajectories run by animals using allocentric navigation exhibited higher neural correlations than egocentric, suggesting that allocentric strategies induce a more consistent spatial encoding in CA1. Moreover, we compared combinations of symmetrical trajectories that, although differing in place, are equivalent in egocentric coordinates. We found that the neural similarity between pairs of symmetrical trajectories was lower than identical trajectories for allocentric animals, whereas for egocentric no difference was observed.Our study provides further evidence of the role of hippocampal spatial cognitive maps in action planning and execution, suggesting spatial selectivity is a consequence of navigational strategy.