Navigation without landmarks: Can rats use a sense of direction to return to a home site?

Abstract

The primary objective of this work was to test whether rats could return to a home site using an internal sense of direction. In two experiments, rats were trained to retrieve a food reward from a central dish on a circular maze. The rats' task was to leave one of eight 'home' locations on the maze periphery, retrieve their food reward and return to the same home box location. In experiment 1 we sought to find out how the rats' navigated to their home boxes by testing: (1) in darkness; (2) in darkness following slow rotation of the rat; and (3) in darkness following rotation of the maze itself. In experiment 2, a new group of rats was tested and extra-maze landmarks were added to the environment. In experiment 1, the rats readily returned to their home box in darkness after being confined to the central dish, and appeared to do so in part by using (non-olfactory) maze surface cues. In experiment 2, rats likewise returned to their home box readily, but did not use the extra-maze cues. When these cues were made ambiguous, the rats returned to their home location: (1) following rotation of the actual home box; (2) following rotation of the maze; and (3) following slow rotation of the rats in the centre dish. The rats displayed an impressive ability to navigate in the absence of landmarks, or when the landmarks were made ambiguous. However, we found little evidence for the use of an internal sense of direction in guiding this navigation.