Thermal images of the mice during a social behavior experiment, showing a urine trail (white trace). Image credit: Peles et al. (CC BY 4.0)
Scientists conduct behavioral experiments on animals to study brain mechanisms that govern social behavior and how these may be affected by various conditions. For example, in rodents, urination and defecation are important social activities used for communication and territory marking, and they are influenced by the emotional state of an individual.
In the past, these activities were analyzed at the end of an experiment by shining ultraviolet light on a filter paper placed on the floor of the cages. However, this method does not provide information on when urination or defecation occurred. Also, in many cases, urine drops are smeared on the filter paper due to the animal's movement during the experiment, which reduces the accuracy of this method. To bridge this gap, Peles et al. developed a computer-vision algorithm – named DeePosit – to automatically track mice's urination and defecation activities during social behavior experiments recorded with a thermal camera.
To examine the efficiency of the tool, the researchers analyzed the urination and defecation activities of mice during several social behavior tests. They then tested whether these activities changed over time and if there were differences between male and female mice, or between different strains of laboratory mice.
The analysis revealed that the tool could identify the time and location of each urination and defecation event with an accuracy similar to that of a human observer. Using this tool, Peles et al. demonstrated that urination and defecation activities changed during a social encounter, for example, urination became more frequent. They observed that males urinated more often than females, which may be attributed to differences in their territorial behavior. It also revealed differences between laboratory strains.
Peles et al. are confident that this rapid, unbiased and cost-effective tool can improve the analysis of social behavior in animals, particularly rodents. This will be especially relevant for researchers investigating the effect of treatments in mouse models of various disorders. The tool can also be trained and adapted to different behavioral and experimental contexts. It may allow a comparison of an additional important aspect of social behavior in treated and non-treated animals, and in health and disease.
