Radial maze type as a determinant of the choice behavior of rats.

Spatial memory of rats was examined in two types of radial mazes in which animals had to obtain food from 6-, 8-, or 12-different arms without repeating choices. In Maze 1 with tubular channels closed at the far end rats returned to the central platform by backing out from the just visited alley. In Maze 2 the tubular channels were equipped with one-way doors at both ends and the central platform was raised 5 cm above the floor. Rats leaving the far end of the alley returned to the central platform through a circular hole in its center. Performance was almost perfect in both apparatuses, but rats preferred to enter adjacent alleys in Maze 1 and widely separated alleys in Maze 2. These behaviors were significantly different from computer-simulated random choice from the set of correct solutions of the task. It is concluded that Maze 2 is better suited for repeated experiments with the same animal because the obligatory return to the center of the platform precludes the simplification of the task by response chaining.