The elevated plus maze is a well-characterized behavioral paradigm, one of the most used tests for anxiety research. The maze contains two open arms and two closed (wall-sheltered) arms and relies upon the animal’s natural tendency to stay in enclosed spaces and their unconditioned fear for open spaces and heights. In short, anxious animals will spend more time in the closed arms than less anxious animals.
The elevated plus maze is very easily automated because it is very suitable for video tracking technology. A camera mounted above the maze and video tracking software is all you need to make your research easier, more reliable, and more efficient. Noldus offers a complete package for the plus maze test, including the elevated plus maze, a camera, and a computer with EthoVision XT video tracking software pre-installed.
Software that's easy to work with
Software should make things easier. One way EthoVision XT does this is with the user-guided set-up. This is a wizard that guides you through selecting animal species, the test you are performing, and other basic settings. EthoVision XT includes a template for the elevated plus maze. With this template, basic settings for your experiment are already made. Of course, you can fine-tune these to your preferences. This way you can get your experiment up and running quickly.
Defining areas of interest: open and closed arms
The plus maze has obvious areas of interest: the open arms versus the closed arms. The amount of time that the animals spend in either of them is of course what you are after in these tests. Thus it makes sense that the variables that EthoVision XT provides (time spent, distance moved) are automatically coupled to these areas of interest. In EthoVision XT, this is called zone definition. You use a still of the video image to define the zones and other points of interest. Then you go about your experiment. After running the trial, EthoVision XT will combine the results with your zone definition.
Examples of results:
- Latency to first enter an open arm
- Time spent in the open arms versus the closed arms
- Total distance moved while in the open arms versus whilst in the closed arms
Automatic detection of behaviors
EthoVision XT detects the center point of each animal. For rats and mice, the software is also able to identify the tail base and nose point. This adds more detail to your data and allows for a more accurate measurement of animal position, enabling you to discriminate between the animal only poking its nose around the corner or moving its entire body into one of the open arms of an elevated plus maze.
Detecting multiple body points also allows EthoVision XT to automatically detect behaviors such as body elongation – characteristic of the stretch-attend posture that is often considered a response to an environment that incites both fear/anxiousness and curiosity.
Experiments running smoothly
You want your experiments running smoothly, and while computers and software will definitely help you accomplish that, you also don’t want to spend all your experiment time behind the computer. That is why EthoVision XT has some smart features to help run your trials in an efficient manner.
To start with, you can program EthoVision XT to automatically start and stop the tracking of your animal. This can be based on detection of the animal, a certain behavior, or timing. For example, you can place your animal in the center square and let EthoVision XT start tracking as soon as the animal is detected in the maze and program it to stop tracking five minutes after that.
If you are tracking live (not from video files), you can collect a series of trials from a live video feed. This means that you don’t have to start each trial manually. You set the start and stop conditions for your trials and then also select a trial-interval. This way, you will have time in between trials to remove the animal from the maze, clean up, and place the next animal. Trials will start only when the interval has elapsed and start conditions (animal was detected in the center square, for example) have been met. This way you can run a complete experiment without having to come back to the computer in between.
Batch acquisition and automatic analysis
If you are tracking from pre-recorded video files, you can use batch acquisition and batch analysis. This is especially useful if you have large data files. First, make a list of all the trials and connect the correct video files to them. Then define how you want to select your data (e.g. only data from the first five minutes of the test) and how the analysis should look (time spent, distance moved). Then it only takes one push of a button and your data will be acquired and analyzed in one go. Even overnight!
Data interpretation is, of course, a crucial step in your research. EthoVision XT provides you with the useful parameters and data selection tools to perform this step. Of course you get raw data as well as calculated results and statistics. There are also a number of ways to present your data visually.
You can visualize your data in tables, graphs, superimposed over your video image, and even in heatmaps. You can do this afterwards, but also during your data collection or before in-depth analysis.
Integrated visualization plots your data dynamically in one synchronized view with the video of the trial. Heatmaps give a dynamic representation of how your animal spent its time. You can select the data you want to appear in your heat map and sort a series of heatmaps in such a way that you can easily compare between trials, between individuals, or between groups. They are also suitable to use in publications and presentations.
Statistics are of course presented in tables, but also in graphs. It is a good way to compare individuals or the results between treatment groups of phases of an experiment.