The Open Field Test is a measure of rodent anxiety-like behavior. The rodent’s natural “anxious” tendency is to spend time in the outer borders of the chamber, close to the walls; this is called thigmotaxis. A rodent exhibiting decreased anxiety will spend more time in the center of the chamber, where it is unprotected by the walls. If only measuring anxiety-like behavior, measure time spent in the outside of the field and time spent in the center of the field (in this case, “center” refers to the 33cmx33cm square shape in the center of the field). You can also use the Open Field Test to look at locomotion (distance traveled and velocity), as well as exploratory behaviors (rearing).
This protocol is adapted from Tye, et al., 2013 (doi: 10.1038/nature11740) and was originally designed to be used with optogenetic stimulation. If you are performing an Open Field Test without stimulation, you can decrease the time to 10 minutes.