Spatial learning by rats across visually disconnected environments

Abstract

Experiments were designed in which some properties of spatial representations in rats could be examined. Adult subjects were trained to escape through a hole at a fixed position in a large circular arena (see Schenk, 1989). The experiments were conducted in the dark, with a limited number of controlled visual light cues, in order to assess the minimal cue requirement for place learning. Three light cues identical in shape, height, and distance from the table were used. Depending on the condition, they were either permanently on or alternatively on or off, contingent on the position of the rat in the field. Two questions were asked: (1) How many identical visual cues were necessary for spatial discrimination in the dark, and (2) could rats integrate the relative positions of separate cues, under conditions in which the rat was never allowed to perceive all three cues simultaneously. The results suggest that rats are able to achieve a place discrimination task even if the three cues necessary for efficient orientation can never be seen simultaneously. A dissociation between the discrimination of the spatial position of the goal and the capacity to reach it by a direct path suggests that, with a reduced number of cues, prolonged locomotion might be required for accurate orientation in the environment.