Maintained Directional Navigation Across Environments in the Morris Water Task Is Dependent on Vestibular Cues

An experiment was designed to test the hypothesis that an internally generated sense of spatial orientation contributes to navigation by rats in the Morris water task and to determine whether this strategy is dependent on vestibular cues. Rats were trained in a standard hidden platform procedure in which they received 8 daily swim trials. In a probe test, rats were carried in an opaque box to a pool located in a novel adjacent environment. During transport, 1 cohort of rats received a disorientation procedure, composed of gentle rotation in the box, while a second cohort served as transport controls. Upon being placed in the pool in the novel room, controls displayed a preference for the pool quadrant predicted by a retained directional response across rooms, whereas disoriented rats failed to display a preference for the same quadrant. Furthermore, control rats swam faster and more directly toward the target quadrant. Together, these findings suggest that rats retain a directional response based on vestibular cues across environments, which can be used to disambiguate geometrically equivalent locations in a novel room and apparatus.