Mouse can recognize other individuals: Maternal exposure to dioxin does not affect identification but perturbs the recognition ability of other individuals

In traditional experiments, mice could discriminate between familiar and unfamiliar individuals. Herein, we report a novel “target-following task (TFT)” in the IntelliCage system to assess mice ability to identify and recognize a specific individual and its role under group-housed conditions. IntelliCage enables us to assign the correct out of four locations in the cage using drinking water as a reward. In the TFT, the correct location of the “follower” mouse was assigned as the location spontaneously chosen by the “target” mouse: the follower must identify its target mouse among multiple followers and targets (>10 mice in total). After training, the follower succeeded to identify its target after training. In the reversal phase, a novel target mouse from group-housed mice was assigned. The follower mice successfully adapted to the new target mouse, indicating that mice can recognize swapping of individual’s role. We next examined the effects of maternal exposure to dioxin, an environmental chemical reported to induce cognitive inflexibility in mice as well as an imbalance of cortical/subcortical activities. Dioxin-exposed mice showed lower performance in the reversal phase. These findings indicate that while maternal exposure to dioxin has no effect on identification, it perturbs the recognition ability of other individuals. The TFT could provide novel insights into investigating social behavior in mice.