title: Network analysis of rat spatial cognition: behaviorally-established symmetry in a physically asymmetrical environment.
abstract: BACKGROUND
  We 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  While 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
  The 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.
authors: Department of Zoology, George Wise Faculty of Life Sciences, Tel Aviv University, Tel-Aviv, Israel.
authors: Shahaf
authors: S
authors: Weiss
authors: Osnat
authors: O
authors: Yaski
authors: David
authors: D
authors: Eilam
authors: Juval
authors: J
authors: Portugali
authors: Efrat
authors: E
authors: Blumenfeld-Lieberthal
mesh_terms: D000818:Animals; D003071:Cognition / Q000502:physiology*; D004777:Environment; D008124:Locomotion / Q000502:physiology; D008297:Male; D008959:Models, Neurological; D009415:Nerve Net; D051381:Rats; D017208:Rats, Wistar; D013037:Spatial Behavior / Q000502:physiology*