Landmark discrimination in the rat: a measure of allocentric spatial ability.

A landmark discrimination task similar to that previously used with monkeys was adapted to measure allocentric spatial ability in rats. Rats were trained to approach one of two food wells, placed 36 cm apart, based on the proximity of the landmark. During initial training, the landmark was adjacent to the baited food well (0 cm). As training progressed, the distance of the landmark from the baited food well was increased in 1.25-cm increments. Results show that rats were able to successfully use a landmark as an external referent up to a distance of 11 cm (when the midpoint between food wells was 18 cm). Following the stepwise training phase, a 64-trial test of mixed distances was administered, and performance was above 80% up to and including 12.5 cm from the near landmark. The results suggest that this landmark discrimination task provides a means to assess allocentric spatial ability in rats and to explore underlying neural mechanisms across species.