Novel object recognition

To assess non-social memory, a novel object recognition paradigm was used. All testing and habituation occurred in the dark and the behaviors were recorded using a camera equipped with an infrared detector. Rats were first habituated over 2 d to a plastic box (61 × 41 cm) for 10 min each day. On the third day, rats began the novel object recognition test by being familiarized with two identical objects placed in opposite corners of the box for 5 min. Rats were returned to their home cage, then returned 1 h later to the box with one of the objects switched for a new (“novel”) object. The time the rat sniffed the “familiar” object versus the novel object was determined. DI was calculated using the following equation: [(time sniffing novel object) – (time sniffing familiar object)]/[(time sniffing novel object) + (time sniffing familiar object)].