Place cells on a maze encode routes rather than destinations.

Roddy M Grieves,Emma R Wood,Paul A Dudchenko

doi:10.7554/elife.15986

Abstract

Hippocampal place cells fire at different rates when a rodent runs through a given location on its way to different destinations. However, it is unclear whether such firing represents the animal's intended destination or the execution of a specific trajectory. To distinguish between these possibilities, Lister Hooded rats (n = 8) were trained to navigate from a start box to three goal locations via four partially overlapping routes. Two of these led to the same goal location. Of the cells that fired on these two routes, 95.8% showed route-dependent firing (firing on only one route), whereas only two cells (4.2%) showed goal-dependent firing (firing similarly on both routes). In addition, route-dependent place cells over-represented the less discriminable routes, and place cells in general over-represented the start location. These results indicate that place cell firing on overlapping routes reflects the animal's route, not its goals, and that this firing may aid spatial discrimination.

Highlights

A long-standing view of the hippocampus is that it contains a neural representation of space, a ‘cognitive map’ (Tolman, 1948), that encodes locations via the spatial receptive fields of place cells (O’Keefe and Nadel, 1978; O’Keefe, 1999)
When a rat repeatedly traverses the same location on its way to different destinations, the place fields of hippocampal place cells are strongly modulated by where the animal is going or where it has come from (Wood et al, 2000; Frank et al, 2000; Ferbinteanu and Shapiro, 2003; Bower et al, 2005; Ainge et al, 2007; Ji and Wilson, 2008; Pastalkova et al, 2008; Ferbinteanu et al, 2011; Allen et al, 2012; Catanese et al, 2014; Ito et al, 2015)
Rats (n = 8) were trained on a task in which they travelled from a start box to one of three goals boxes (Left, Centre, Right) to obtain a food reinforcement (Figure 1A,B)

Summary

Introduction

A long-standing view of the hippocampus is that it contains a neural representation of space, a ‘cognitive map’ (Tolman, 1948), that encodes locations via the spatial receptive fields of place cells (O’Keefe and Nadel, 1978; O’Keefe, 1999). When a rat repeatedly traverses the same location on its way to different destinations, the place fields of hippocampal place cells are strongly modulated by where the animal is going or where it has come from (Wood et al, 2000; Frank et al, 2000; Ferbinteanu and Shapiro, 2003; Bower et al, 2005; Ainge et al, 2007; Ji and Wilson, 2008; Pastalkova et al, 2008; Ferbinteanu et al, 2011; Allen et al, 2012; Catanese et al, 2014; Ito et al, 2015) This suggests that place cells represent not just near instantaneous location (Muller and Kubie, 1989), and aspects of the animal’s goal directed behaviour. One interpretation of this ‘splitter cell’ pattern of firing (hereafter differential firing) is that it represents the animal’s intended destination

Methods

Results

Discussion

Conclusion