2.6. Novel Object Recognition Test

The day following the Open Field Test SED (n = 9), LOW (n = 10), and HI (n = 7) mice were acclimated to the test area for 20 min. The next day each mouse was subjected to a sample trial and a test trial. The objects consisted of 6 each of glass votive size candle holders and similar sized small metal baskets that had been determined to be of equal interest in a broad object screening with a test group of mice in pilot studies [15]. Presentation of the votive or basket as the novel object and side of novel object was counterbalanced across groups. During the sample trial, the mouse was exposed to two identical objects placed in opposite corners of the test area for 10 min. The mouse was then returned to his cage for 50 min. Following the delay, the mouse was put back into the test area for 10 min with one of the objects from the sample trial replaced with a novel object. The test area and objects were cleaned with 70% ethanol after each trial. All sessions were recorded using Any-Maze software. Time spent investigating each object was timed manually from the recordings using a stopwatch. Active investigation was defined as the mouse facing the object within close proximity (2 cm) and/or touching the object with forepaws.