Network Analysis of Rat Spatial Cognition: Behaviorally-Established Symmetry in a Physically Asymmetrical Environment

Abstract

BackgroundWe set out to solve two inherent problems in the study of animal spatial cognition (i) What is a “place”?; and (ii) whether behaviors that are not revealed as differing by one methodology could be revealed as different when analyzed using a different approach.MethodologyWe applied network analysis to scrutinize spatial behavior of rats tested in either a symmetrical or asymmetrical layout of 4, 8, or 12 objects placed along the perimeter of a round arena. We considered locations as the units of the network (nodes), and passes between locations as the links within the network.Principal FindingsWhile there were only minor activity differences between rats tested in the symmetrical or asymmetrical object layouts, network analysis revealed substantial differences. Viewing ‘location’ as a cluster of stopping coordinates, the key locations (large clusters of stopping coordinates) were at the objects in both layouts with 4 objects. However, in the asymmetrical layout with 4 objects, additional key locations were spaced by the rats between the objects, forming symmetry among the key locations. It was as if the rats had behaviorally imposed symmetry on the physically asymmetrical environment. Based on a previous finding that wayfinding is easier in symmetrical environments, we suggest that when the physical attributes of the environment were not symmetrical, the rats established a symmetric layout of key locations, thereby acquiring a more legible environment despite its complex physical structure.Conclusions and SignificanceThe present study adds a behavioral definition for “location”, a term that so far has been mostly discussed according to its physical attributes or neurobiological correlates (e.g. - place and grid neurons). Moreover, network analysis enabled the assessment of the importance of a location, even when that location did not display any distinctive physical properties.

Network analysis of exploratory behaviors of mice in a spatial learning and memory task

“…In the dynamic node generation, a node was generated at the coordinates of each point where a particular action occurred [ 31 ]. In the present analysis, stopping behavior was picked as a representative action, and other criteria were also based on a previous analysis [ 31 ]. When the traveling distance within five successive frames was less than the threshold, one stopping coordinate was generated at the centroid of the points during the frames.…”

“…The threshold was set at 20 pixels, which was approximately half of the average mouse’s body length. Then, a node was generated on a centroid of stopping coordinates set using the City Clustering Algorithm (CCA) [ 31 , 32 ]. In short, the CCA recursively processed data using the following three steps until a convergence condition was satisfied.…”

The GLP-1 receptor agonists exendin-4 and liraglutide alleviate oxidative stress and cognitive and micturition deficits induced by middle cerebral artery occlusion in diabetic mice

“…In the conditioning session, the animals were placed individually in a conditioning chamber (60 × 60 × 60 cm) for 2 h. Each chamber contained 2 objects: sawdust (nontarget object) and feed (target object). For the test session, the animal was placed in the same chamber for 15 min, and activity was recorded using a high-throughput-screening top-view camera (STD-CA67D-IR; Sony, Tokyo, Japan) and ObjectScan behavior analysis software (Clever Sys Inc., Reston, VA, USA) [ 3 , 47 ]. Time spent exploring each object was recorded to assess cognitive behavior.…”

Obsessive-compulsive disorder: Insights from animal models

“…In those studies, behavior was regarded as intervals of travel that are interrupted by stops (stationary episodes). Accordingly, the analysis was based on scoring: (i) the sets of movements that rats perform when they are stationary in a specific locale; and (ii) the trajectories of the routes connecting these locales, assuming that during locomotion rats cannot perform movements like rearing and grooming that they perform when stationary (Eilam and Golani, 1989; Eilam et al, 1989; Weiss et al, 2012). Notably, the application of this approach revealed numerous similarities between spatial behavior in humans and in rodents (for a comprehensive review, see Eilam, 2014).…”