A purely geometric module in the rat's spatial representation

Rats were tested in place finding tasks in a rectangular environment with distinct featural panels in the corners, such as the example in Figure 1A. When given a target place to seek, they made a systematic error both in a working memory paradigm and in a reference memory paradigm: they sometimes searched at the point located at 180° rotation from the target through the centre. In a working memory paradigm, these rotational errors were almost as numerous as correct searches. The target and its rotational equivalent have the same geometric relations to the arrangement of surfaces as surfaces, or the shape of the environment, but differ in their relations to non-geometric properties such as the brightness or texture of a surface. In making systematic rotational errors, the animal must have been using some record specifying only the target's geometric relations to the shape of the environment, and not its relations to the arrangement of non-geometric information. Further tests showed that rats could use the non-geometric information, but that they primarily checked features near a geometrically specified target address, that is, an address specified by its geometric relations to the shape of the environment alone. They did not seem to use the overall arrangement of non-geometric features. It is theorized that in orienting in space by using landmarks, the rat uses primarily a purely geometric module, which also serves as a basis for coordinating the locations of non-geometric data.