Preweanling rats solve the Morris water task via directional navigation

Abstract

Adult rats show a preference for directional navigation over place navigation in the Morris water task. Here, the authors investigated whether preweanling rats with a newly developed ability to perform the water task also solve the task via directional navigation. After 24-day-old rats were trained to find a hidden platform in a fixed spatial location, a no-platform probe trial was conducted with the pool either in the same position as that used during training (no shift group) or shifted to a new position in the room (shift group). The authors found that rats in the shift group did not search for the platform at its absolute spatial location but rather navigated in the same direction that the platform was located during training and searched at the correct distance from the pool wall, resulting in a search at a location that was never trained. This pattern of results suggests that young rats learn to solve the water task by navigating in a particular direction rather than navigating to a precise place--a finding that may have implications for understanding hippocampal development.