SPATIAL-LEARNING BY RATS ACROSS VISUALLY DISCONNECTED ENVIRONMENTS

Two Spatial tasks were designed to test specific properties of spatial representation in rats. In the first task, rats were trained to locat e an escape hole at a fixed position in a visually homogeneous arena. This arena was connected with a periphery where a full view of the roo m environment existed. Therefore, rats were dependent on their memory trace of the previous position in the periphery to discriminate a posi tion within the central region. Under these experimental conditions, t he test animals showed a significant discrimination of the training po sition without a specific local view. In the second task, rats were tr ained in a radial maze consisting of tunnels that were transparent at their distal ends only Because the central part of the maze was non-tr ansparent, rats had to plan and execute appropriate trajectories witho ut specific visual feedback from the environment. This situation was i ntended to encourage the reliance on prospective memory of the non-vis ited arms in selecting the following move. Our results show that acqui sition performance was only slightly decreased compared to that shown in a completely transparent maze and considerably higher than in a tra nslucent maze or in darkness. These two series of experiments indicate (1) that rats can learn about the relative position of different plac es with no common visual panorama, and (2) that they are able to plan and execute a sequence of visits to several places without direct visu al feed-back about their relative position.