The novel object recognition test was conducted with Cohort 2 mice in the open field arena, using methods previously described (Bevins and Besheer, 2006 (link)). The experiment consisted of two habituation sessions, a 10 min familiarization session, and a 5 min recognition test. On day 1, each subject was habituated to a clean empty open field arena for 30 minutes. Twenty four hours later, each subject was returned to the open field arena for a second habituation phase, this time for 10 min. The mouse was then removed from the open field and placed in a clean temporary holding cage for approximately 2 min. Two identical objects were placed in the arena. Each subject was returned to the open field in which it had been habituated, and allowed to explore freely for 10 min. After the familiarization session, subjects were returned to their holding cages, which were transferred from the testing room to a nearby holding area. The open field was cleaned with 70% ethanol and let dry. One clean familiar object and one clean novel object were placed in the arena, where the two identical objects had been located during in the familiarization phase. One hour after the familiarization session, each subject was returned to its open field for a 5 min recognition test, during which time it was allowed to freely explore the familiar object and the novel object. The familiarization session and the recognition test were videotaped and subsequently scored by two highly-trained investigators, uninformed of genotype, whose inter-rater reliability was ≥95%. Object investigation was defined as time spent sniffing the object when the nose was oriented toward the object and the nose-object distance was 2 cm or less. Recognition memory was defined as spending significantly more time sniffing the novel object than the familiar object. Total time spent sniffing both objects was used as a measure of general exploration. Time spent sniffing two identical objects during the familiarization phase confirmed the lack of an innate side bias.