Volumetric spatial behaviour in rats reveals the anisotropic organisation of navigation

Abstract

We investigated how access to the vertical dimension influences the natural exploratory and foraging behaviour of rats. Using high-accuracy three-dimensional tracking of position in two- and three-dimensional environments, we sought to determine (i) how rats navigated through the environments with respect to gravity, (ii) where rats chose to form their home bases in volumetric space, and (iii) how they navigated to and from these home bases. To evaluate how horizontal biases may affect these behaviours, we compared a 3D maze where animals preferred to move horizontally to a different 3D configuration where all axes were equally energetically costly to traverse. Additionally, we compared home base formation in two-dimensional arenas with and without walls to the three-dimensional climbing mazes. We report that many behaviours exhibited by rats in horizontal spaces naturally extend to fully volumetric ones, such as home base formation and foraging excursions. We also provide further evidence for the strong differentiation of the horizontal and vertical axes: rats showed a horizontal movement bias, they formed home bases mainly in the bottom layers of both mazes and they generally solved the vertical component of return trajectories before and faster than the horizontal component. We explain the bias towards horizontal movements in terms of energy conservation, while the locations of home bases are explained from an information gathering view as a method for correcting self-localisation.

Irregular distribution of grid cell firing fields in rats exploring a 3D volumetric space

“…Given previous findings that place cells express spatially localized firing fields in volumetric space 7 and that rats can navigate accurately in the lattice maze 17 , 18 , our results suggest that place cells and spatial mapping can perhaps function even when grid cell firing fields are irregularly distributed 18 . It may be that place cells do not require grid cell inputs for positioning when visual cues are available 28 , although future studies that simultaneously record place and grid cells in three dimensions, in the presence and absence of visual cues, are needed to fully explore this relationship.…”

“…We considered a ‘crossing’ to have occurred when the head of the rat moved from one unit to another. A detailed analysis of the behavioral data can be found elsewhere 17 and so only brief results related to grid cell activity are reported in the present study.…”

Human Navigation in a Multilevel Travelling Salesperson Problem

“…Taken together, our converging results from the structure mapping task as well as from the M-TSP task provide new behavioural evidence for a horizontal bias in volumetric spatial cognition and behaviour. This is in line with the literature from animal research (Grieves et al, 2021;Jedidi-Ayoub et al, 2021;Jovalekic et al, 2011). We have also…”

“…An alternative explanation is that there is a difficulty associated with externalising representations of 3D space on a 2D space medium. Overall this results supports the theory of anisotropy of organisation of cognitive maps (Brandt et al, 2015;Jedidi-Ayoub et al, 2021) and the theory of horizontal bias (Jovalekic et al, 2011).…”

On heights and plains: How rodents from different habitats cope with three-dimensional environments?

“…Rodents set their home-base near a salient landmark [ 19 ], which in an empty arena (open-field) is usually in one of the corners, perhaps due to the sense of safety [ 20 , 21 ]. In more complex environments, it was found that rats tend to set their home-base at a vantage point [ 22 ]. The majority of studies on spatial behavior in rodents was performed in two-dimensional laboratory environments.…”