The overall goal of this procedure is to assess motor coordination and balance in mice. The first step is to assemble a balance beam with motion detector's position to record the latency of beam crossing to begin training maer placed on the starting point of the balance beam and allowed to cross to a safe platform. It is sometimes necessary to encourage the animal along the beam toward the end point.
After an inter trial interval of 10 minutes, maer then trained on a narrower beam to allow for greater sensitivity. The final step of the procedure is to test the trained animals on beams of different widths. Ultimately, results can be obtained that show deficits in motor coordination and balance.
Hi, I am Tim Luong and I'm an MD PhD candidate in the biology department at the California Institute of Technology. I'm Holly Carlisle and I'm a postdoc at the California Institute of Technology in the biology department, and today we're going to be showing you how to assess balance and motor coordination in mice using the balance beam test. Now, the main advantage of this technique compared to other methods such as the rotor rod, is that the balance beam test tends to be more sensitive to even subtle deficits in motor coordination.
This method can help answer key questions in the behavioral field, such as whether our motor coordination and balance are affected in certain neurological disease models and whether our motor deficits are alleviated by particular treatments. The purpose of this test is to measure the amount of time it takes for a mouse to cross the beam without stopping or stalling and without prompting from the investigator. In order to get a clean run on test day, we train for two days prior to testing.
Visual demonstration of this method is helpful as the way the mice are handled and aided across the beam may be difficult for those less familiar with behavioral testing. So let's get started. This protocol is based on those of Southwell, etal and Carter etal.
The apparatus is assembled by resting a beam that is one meter long between two 50 centimeter high poles. The beams have a flat surface of six or 12 millimeters wide. Beams of greater widths can be used for larger mice and those not able to cross the narrower sizes.
A black box is placed at the end of the beam and nesting material is placed inside the black box to encourage the mouse towards the finishing point, illuminate the starting point with a lamp to serve as an aversive stimulus. Motion detectors are placed at zero and 80 centimeters to record the latency of beam crossing, stretch a nylon hammock below the beam and approximately 7.5 centimeters above the tabletop to cushion any falls. The mice used in this procedure are housed on a 12 hour light dark cycle and have been acclimated for two weeks prior to testing.
Introduced the animals to the test room approximately 10 minutes before beginning the experiment and use a cohort of at least 10 mice per test condition for the best results. To begin training, place a mouse on the start location of a 12 millimeter wide beam. The timer starts when the nose of the mouse enters the center 80 centimeters and stops when the animal reaches the end of the 80 centimeters.
Mice should cross the beam with a minimal amount of stopping or stalling. If the animal stops moving forward, encourage them to continue by gently prodding them from behind. Once the animal has successfully traversed the beam, remove it from the safe box and place it back into the home cage for 10 minutes before beginning the next training session.
The balance beam and box are cleaned and wiped with 70%ethanol before introducing the next mouse. Each mouse is trained on the 12 millimeter wide beam three times followed by training on the six millimeter wide beam. An additional three times over training may increase the occurrence of stalling as the animal becomes more familiar with the task and apparatus.
On the other hand, if mice fail to traverse the entire beam successfully after two days of training, additional training may be required. Be sure to record baseline measurements before the animals receive any treatment. After training is complete for the day, return mice to their home cages into the holding facility.
On the day of testing, bring the animals into the room 10 minutes before beginning the experiment as shown previously, place a mouse in the start location and record the latency for the animal to traverse the center 80 centimeters of the beam. The data are reported as the average of two successful trials in which the mouse crossed directly to the end without stopping and without prodding by the investigator. Video recordings can be used for finer analysis of slipping and other observable motor deficits.
In this example, nine to 11 week old C 57 black six mice were tested on 12 millimeter and six millimeter wide beams. The average time to cross the 12 millimeter wide beam was 4.6 plus or minus 0.4 seconds for males, and 3.3 plus or minus 0.3 seconds for females times on the six beam were 6.8 plus or minus 0.7 seconds for males and 5.9 plus or minus 0.5 seconds. For females.
Balance beam performance may vary depending on the age and strain of mice. The C 57 black six mice used in this example are typically active animals, a few slips, but no falls were observed for these mice and genetically or pharmacologically manipulated animals, slips and falls may become more frequent and can be quantified. Impaired mice may clinging onto the side of the beam, which increases their time to cross While attempting this procedure.
It's important to be persistent and consistent in prodding the mice to move forward if they stall or get distracted on the beam. After watching this video, you should have a good understanding of how to train mice to cross the balance beam and to assess their balance and coordination. Thanks for watching and I hope you found this helpful.
