Effects of environmental enrichment on exploratory behavior, win-stay and lose-shift performance, motor sequence learning, and reversal learning during the three-lever operant task in mice.

Beneficial effects of environmental enrichment (EE) on the central nervous system have been demonstrated. Although the effects of EE on spatial learning have been extensively studied, studies on reward-based motor learning are limited. In this study we examined the effects of EE on the performance of operant tasks using three levers (A-C). Mice were divided into two groups and housed either in the control condition or in the physical EE condition. The mice were trained in three types of operant tasks in sequence. First, mice were trained to press one of the active levers for a food reward (one-lever task). Second, mice were trained to press the three levers in the order of A, B, and C (three-lever task). Third, the lever order was reversed to C, B, and A (reverse three-lever task). We found some behavioral differences between control and EE mice. When all three levers were active in the one-lever task, mice tended to press the three levers equally at first, then shifted to press one lever preferentially. This behavioral shift from exploration to exploitation was delayed in EE mice. When only one lever was active, EE mice showed a higher lose-shift performance. In the three-lever and reverse three-lever tasks, EE mice pressed three levers more often and acquired more food rewards, compared to control mice, although the success rate in both tasks was not different between the two groups. These behavioral features observed in EE mice (higher lose-shift performance and higher trial and error activity) might be advantageous when circumstances are not stable.