How do global and local geometries shape exploratory behavior in rats?

The present study examines how rats process object information in relation to other objects as well as to the global shape of an enclosure. Rats were introduced into either a round or a square arena with various arrays of freestanding portable corners (objects) that differed in spacing, orientation, and number. We found that the time spent at the objects was substantially higher in the round compared with the square arena. Rats in the square arena distributed their time evenly between arena perimeter and objects; however, they visited the objects more frequently than the perimeter. Rats tested in either round or square arena favored staying at the interior of the object regardless of its orientation in the arena. Finally, only geometric changes in the object array affected the rats’ level of activity. These findings demonstrate that the rats were able to detect the geometry of the enclosure, the array, and the objects. We suggest that the context of the global enclosure geometry affects the meaning of landmarks (objects) for the observer, which in turn results in a different distribution of activity. Specifically, an object's local geometry served mainly in the context of a safe place in the round arena, as manifested in extended duration of stay at the objects, however in the square arena served mainly as a place of interest, as manifested in the frequent visits, but without their staying there. Thus, the geometries of the enclosure, the object array, and the discrete objects, together shape exploratory behavior in rats.