Zero maze for testing anxietylike behaviors. The zero maze is elevated approximately 18 in above the floor, and it consists of two open and two closed areas. Mice are permitted free exploration of the maze for 5 min. Illumination of the maze is critical and should be maintained between 40 to 60 lux. Anxious mice remain in the closed areas and do not venture onto the open areas of the maze. The percent time spent in the open areas is taken as an index of anxiety in the mouse.