The overall goal of this study is to establish a positive reinforcement training for mice as a specific handling program. This method can answer key questions in the emerging field of refinement strategies for laboratory mice such as how to reduce stress levels in keeping and performing experiments. The main advantage of this technique is that is can be modified to various purposes and that it can help to improve the well being of laboratory mice.
We first had the idea for this method when we thought about ergonomic alternatives to transfer mice between cages without touching them. Visual demonstration of this method is critical as the technique is challenging to learn because the timing and overall handling of the mice are essential. Before beginning the experiment, transfer the home cage to a quiet environment.
Then remove all objects form the home cage to use it as a training area. Then transfer the cage companions out of the home cage leaving only one training mouse. To start the training, set the timer to five minutes and press start.
Add the mouse tunnel to the home cage near a wall. Then wait until the mouse inspects the tunnel. As soon as the mouse enters the tunnel, click and present the reward at the end of the tunnel.
While the mouse sits and feeds on the reward in the tunnel tenuously click for 15 seconds. As soon as the mouse leaves the tunnel, repeat the session again. On days two through five, set the timer to five minutes.
Press start and add the mouse tunnel to the home cage. As soon as the mouse enters the tunnel, click and present the reward at the end of the tunnel. Repeat this for the next 30 seconds and then pause for 15 seconds to take the tunnel out of the cage.
Then add the tunnel again and click immediately when the mouse reenters the tunnel. Present the reward at the end of the tunnel and allow the mouse to gnaw on it for up to one second. Then take away the reward.
Finally, as soon as the mouse starts reentering the tunnel by itself, present the reward in front of the end of the tunnel. During week two, begin by setting the timer to five minutes. Press start and place the globe at the end of the target stick in the cage.
As soon as the mouse touches the globe with its nose, click and present the reward next to the globe. After the mouse has linked the performed action to the reward, change the position of the globe during the training session. Reward the mouse after it touches the globe with its nose in the new position.
Next place the globe in the cage and shortly before the mouse touches the globe, slowly and carefully change the position of the globe by one centimeter. Click and reward if the mouse has crossed the distance and touches the globe. Slowly extend the distance the mouse has to cross and repeat this procedure until the mouse follows reliably.
During week three begin by placing one hand in the training cage while holding the clicker target stick combination and the reward with the other hand. Set the timer to five minutes. Press start and place the globe at the end of the target stick next to the hand.
As soon as the mouse shows interest in the globe, click and present the reward next to the globe. Finally, place the globe on the palm of the hand. Then click and reward while the mouse is sitting on the palm of the hand.
After clicker training, the vast majority of trained mice all female mice and 83 percent of male mice followed the target stick. Female mice displayed higher motivation for training in general form the respective behavior with the higher frequency throughout the training sessions. Trained mice displayed a significantly lower frequency of anxiety related behaviors than untrained mice.
Furthermore, depression related floating behavior during the Morris water maze was significantly reduced in the trained group. Once mastered, this technique can be completed in three to five minutes per mouse, per day if it is performed properly. While attempting this procedure, it's important to remember to handle mice in a gentle, calm, and confident manner.
Following this procedure, other methods like teaching mice to run over a bridge to transfer on another cage independently can be performed to improve health and hygiene conditions in animal facilities. After its development, clicker training contributes to refinement as it can be considered as a form of cognitive enrichment. After watching this video, you should have a good understanding of how to implement positive reinforcement training for mice in laboratory animal facilities.
