A modification of the block test was employed as previously described by Fleming et al. (2008). The block test evaluated the mouse’s ability to detect social scents and distinguish between familiar and novel scents, an ethologically important behavior in mice. In this test, individually housed animals were habituated to a stimulus by placing three small empty plastic tissue cartridges (Fisher Scientific, Pittsburgh, PA, USA) in each animal’s cage for 7 d. During this time, the cage bedding was not changed, so that the plastic cartridges took on the odor of that animal. On the day of the test, the stimulus was removed from the cage, and animals were transferred into a separate testing area where water bottles, food, and metal cage grids were removed and just the filtered cage lid remained on each cage. Animals were habituated to the room for 1 h. First, one familiar plastic cartridge was placed in the testing cage, and the animal adapted to this familiar stimulus for an additional 15 min. Second, another familiar plastic cartridge was placed in the testing cage, and behavior
