Figure 15. The Barnes maze consists of a circular surface with 40 holes around the perimeter.

An escape tunnel is located beneath one of the holes. Mice are trained to locate a hidden escape tunnel, and each trial starts by placing the mouse in the start cylinder (A). The trial starts by removing the start cylinder. Additionally, mice are trained to locate a visible escape tunnel, which changed locations each session, by placing a coloured object directly behind the hole containing the escape tunnel. Inset: close-up of the escape tunnel (B) the mouse is searching for.