Figure 1.

Schematic representation of experimental procedure. On day 1, for the familiar groups, mice were pre-exposed to the open field under dim light for 30 min. On the test day, novel groups were exposed to the open field for the first time in two lighting conditions: dim (Blue: 20–40 lux) and bright (Yellow: 400–500 lux). USVs were recorded for the first 5 min. Box without lines represents Novel and Box with the lines represents Familiar conditions. Each arrowed bar represents 30 min. A red bar represents 5 min. USVs: ultrasonic vocalizations.