Rearing environment and radial maze exploration in mice

The effect of an enriched rearing environment on exploration of 4- and 8-arm radial mazes was investigated in CD-1 mice. Subjects in enriched (EC) and standard (SC) environmental conditions were socially reared with the exception that various objects and a running wheel were added into the EC cages. Non-deprived subjects were allowed to explore individually an appropriate maze for 10-min periods on two successive days (Days 1 and 2 of the experiment). After the second exploration session subjects were deprived of water for 12 h before the test which was administered on Day 3 of the experiment. Subjects from both groups performed similarly in the 4-arm radial maze, finding the arm containing water with comparable latency and erroneous entries to other, not containing water, arms. However, the more complex, 8-arm radial maze significantly differentiated the behaviour of both groups. EC subjects showed faster habituation to the maze than SC subjects, decreasing significantly their locomotor behaviour during second exploratory session. During the test, EC subjects found and drank water within significantly shorter time, making fewer errors. It is suggested that subtle behavioural changes caused by different rearing environments might be more readily detectable in the early phases of solving more complex behavioural tasks by mildly motivated animals.