Open field (animal test)

Animals such as rats and mice display a natural aversion to brightly lit open areas. However, they also have a drive to explore a perceived threatening stimulus. Decreased levels of anxiety lead to increased exploratory behavior. Increased anxiety will result in less locomotion and a preference to stay close to the walls of the field (thigmotaxis). == Experimental design ==

The open field is an arena with walls to prevent escape. Commonly, the field is marked with a grid and square crossings. The center of the field is marked with a different color to differentiate from the other squares. In the modern open field apparatus, infrared beams or video cameras with associated software can be used to automate the assessment process. Behavioral patterns measured in the open field test include: • Line crossings – Frequency with which the rodent crosses grid lines with all four paws (a measure of locomotor activity), sometimes divided into activity near the wall and activity in the center. • Center square entries – Frequency with which the rodent enters the center square with all four paws. • Center square duration – Duration of time spent in the central square. • Rearing – Frequency with which the rodent stands on its hind legs in the field. Rearing-up behavior in which the forepaws of the animal are unsupported and the similar behavior in which the forepaws rest against the walls of the enclosure have different underlying genetic and neural mechanisms and unsupported rearing might be a more direct measure of anxiety. The paper presents an early validation of an innovative animal tracking tool and a model-based approach to gait analysis. The methodology primarily leverages random walk class models, including fractional Brownian motion (fBm) and its modifications. These models have garnered significant attention in recent years for their applications in animal tracking and behavioral analysis. Unlike traditional approaches that rely on multiple movement parameters or artificial combinations of various models, the fBm-based models are characterized by a limited number of free parameters. These parameters are straightforward to interpret physically, making the models not only efficient but also intuitive. ==Criticisms==

The assumption that the test is based on conflict has been heavily criticized. Critics point out that when measuring anxiety each choice should have both positive and negative outcomes. This leads to more dependable observations which the OFT does not present. When the test was first developed, it was pharmacologically validated through the use of benzodiazepines, a common anxiety medication. Newer drugs such as 5-HT-1A partial agonists and selective serotonin reuptake inhibitors, which have also been proven to treat anxiety, show inconsistent results in this test. Different results can be obtained depending on the strain of the animal. == See also ==