Evidence for a shift from place navigation to directional responding in one variant of the Morris water task.

Previous work from our laboratory has demonstrated that rats display a preference for directional responding over place navigation in a wide range of procedural variants of the Morris water task (Hamilton, Akers, Weisend, & Sutherland, 2007; Hamilton et al., 2008). A preference for place navigation has only been observed when the pool is reduced as a cue by filling it with water.

The relative influence of place and direction in the Morris water task.

Previous work from our laboratory has demonstrated that rats display a preference for directional responding over true place navigation in the Morris water task. The present study evaluated the range of situations in which this preference is observed and attempted to identify methods that favor navigation to the precise location of the escape platform in the room. A preference for directional responding over place navigation was observed in a wide range of procedures that included providing extensive training (Experiment 1), providing only platform placement experience in the absence of active swim training (Experiment 2), training navigation to multiple platform locations in a moving platform variant of the task (Experiment 3), and explicitly training navigation to a precise location in the room, versus navigation in a particular direction, regardless of the pool's position in the room (Experiments 4-5).

Preweanling rats solve the Morris water task via directional navigation.

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).