*2.5. Novel Object Recognition Test*

A novel object recognition (NOR) test was conducted after OFT. NOR is a commonly used behavioral assay for the investigation of various aspects of learning and memory level in mice. NOR is fairly simple and can be completed over 5 days: habituation (3 days), training (day 4), and testing day (day 5). During training, the mouse was allowed to explore two identical objects in the open field area (50 × 50 cm). On testing day, one of the training objects was replaced with a novel object. The exploring time of the novel object and familiar object was recorded within 5 min. The discrimination index (DI) was used to evaluate the learning and memory ability of animals. The DI calculation formula is as follows:

$$\text{DI} = (\text{N} - \text{F}) / (\text{N} + \text{F}) \times 100\%\_{\text{V}}$$

where N is the time spent on novel location/object exploration and F is the time spent on familiar location/object exploration.
