Mice use start point orientation to solve spatial problems in a water T-maze

Behavioral work has demonstrated that rats solve many spatial problems using a conditional strategy based on orientation at the start point. The present study assessed whether mice use a similar strategy and whether the strategy would be affected by the poorer directional sensitivity of mice. In Experiment 1, mice were trained on a response, a direction or one of two place problems to locate a hidden platform in a water T-maze located in two positions. In the response task, mice made a right (or left) turn from two different start points located 180° apart. In the direction task, the maze was shifted (to the left or right) and the start points rotated by 180° across trials, but the platform was in a constant direction relative to room cues. In the translation place task, the mice were trained to locate the platform in a fixed location relative to extra-maze cues when the maze was shifted across trials, but the orientation of the start arm did not change. In the rotation place task, the mice were trained to locate the platform in a fixed location when the maze was shifted and the start points rotated by 90° across trials. As previously reported with rats, mice had difficulty solving the translation place problem compared with the other three problems. Unlike rats, mice learned the direction problem in significantly fewer trials than the rotation problem. This difference between acquisition of the direction and rotation problems was replicated in Experiment 2. The difficulty mice have in discriminating start point orientations that are 90° apart as opposed to 180° apart can be attributed to the broader firing ranges of HD cells in mice compared with rats.