Landmark geometry and identity controls spatial navigation in rats

Abstract

In three experiments, a new reference memory procedure was used to examine how male rats search for consistently located food in a cue- controlled spatial environment. The animal searched the tops of 24 poles for six hidden baits in an enclosed circular arena containing a fixed configuration of six object landmarks. In Experiment 1, acquisition was faster and overall perform new better for the consistent group (10 rats), in which the six baited poles were fixed relative to the landmarks for each session, than for the random group (4 rats), in which baited poles were randomly configured. Cue-control tests and computer simulations suggested that the consistent group relied on the landmarks to directly go to the baited poles, whereas the random group used them to employ a response strategy for searching the arena. Experiment 2 and 3 revealed that the number, identity, and geometric configuration of the landmarks were important to the consistent group search performance. Overall, these results are most consistent with the use of a geometric representation only male rats which includes information about both the identity and the relative geometry of discrete landmarks in the surrounding spatial environment.