Studies using zebrafish models for fear and anxiety related disorders and behavior often focus on bottom dwelling and tank diving in novel tanks or light-dark boxes.
Bottom dwelling behavior and latency to start exploring the upper half of the tank are important indicators of inhibited exploration, which is considered indicative of stress and anxiety. These are useful parameters in the study of anxiolytic and anxiogenic properties of certain compounds. Side-view tracking is a practical approach to measure these parameters.
Set-ups such as open fields and light/dark boxes require a top-view approach to assess whether animals prefer certain sections of the tank.
The location of the fish in the tank, whether seen from a side or top view, is important and relatively straight-forward to measure. However, many researchers argue that anxiety and stress in fish are also indicated by reduced speed and more erratic movements. This is more diffcult to measure manually, but it is an easy task for video tracking software.
Some studies require an in-depth study of swimming behavior (for example those of a range of potential anxiogenic or anxiolytic substances). The challenge here is that fish swim in 3D. A true assessment of path shape, erratic movement, even velocity cannot be fully gained from a side or top view.
The analysis of 3D swim patterns offers a more detailed analysis of the effect of compounds. For example, at the Kalueff Lab (Tulane University, New Orleans, LA, USA) they found that when examining different effects from known anxiolytics and anxiogenics, 3D tracking revealed much more pronounced differences in zebrafish behavior. In addition, some behavioral effects were even undetected when observations were limited to 2D video tracking.
To analyze swim patterns in 3D, researchers can use the Track3D add-on to the video tracking tool EthoVision XT. Based on the calibration of the arena and subsequent combination of the top-view and side-view track from EthoVision XT, Track3D visualizes and analyzes the complete swim path of the fish.