The morris water maze experiment was established by American scientist Richard GM Morris in 1981. It was originally used to study the regulatory effect of brain structure on learning and memory, and gradually developed into the most commonly used model for evaluating animal learning and memory. The basis of this experiment is that rodents have a strong motivation to escape from the water environment and escape from the water environment in the fastest and most direct way. The process of learning to escape from the water environment reflects the learning ability of animals; spatial positioning is based on the surrounding environment, and the purpose is to swim to a safe place (platform) in water, reflecting the spatial memory ability of animals. The morris water maze is performed with rats or mice. The rat water labyrinth experimental equipment made by Shanghai Xinsoft Information Technology Co., Ltd. includes a gray or black circular pool (diameter 200cm, height 100cm; mouse size halved), a platform (diameter 10cm), and a tracking camera And the computer connected to the camera (Figure 25-1). The pool is filled with water, 50cm deep, and the water temperature is 22 ~ 24 ℃. The platform was placed 2 cm below the water surface (1 cm for mice). Add milk powder or milk to the water to stir the water so as not to let the animal see the underwater platform. The camera is located 200cm above the center of the pool, and can record the animal's position, swimming distance and time (so that the swimming speed can be calculated) and swimming path. Extra-maze cues are painted on the walls around the room with brightly colored and differently shaped drawings. There are three processes: acquisition training, exploration and counterpoint training. 1. The acquisition phase theoretically divides the pool into four quadrants, and the platform is placed in the center of one of the quadrants. (1) Put the animal (rat or mouse) into the water with its head facing the wall of the pool, and randomly place it in one of the four starting positions: east, west, south and north. Record the time (s) the animal found the underwater platform. In the previous trainings, if this time exceeded 60s, the animal was guided to the platform. Let the animal stay on the platform for 10s. (2) Remove and dry the animal. If necessary, place the animal (especially the rat) under a 150W incandescent lamp and bake for 5min, and put it back in the cage. Each animal is trained 4 times a day, with an interval of 15-20 minutes between the two trainings, and continuous training for 5 days. 2. Probe training (probe trial 1) The day after the last acquired training, the platform was removed and the 60-s probe training started. Place the animal into the water from the opposite side of the original platform quadrant. Record the time the animal spends in the target quadrant (the quadrant where the platform was originally placed) and the number of times it entered the quadrant, as a detection indicator of spatial memory. 3. Reveral phase measures the working memory of the animal. On the second day after the end of the exploration training, the 4-day counterpoint training began. Place the platform in the opposite quadrant where the original platform is located. The method is the same as for acquired training. Train 4 times a day. Each time the time to find the platform and the swimming distance and swimming speed are recorded. 4. The probing training (probe trial 2) is carried out the day after the last training. The method is similar to the above exploration training. Record the time the animal spends in the target quadrant (the area where the platform is located for the second time) and the number of times it enters the area within 60 seconds. 1. Compared with food-driven models (such as the radial arm maze), the biggest advantage of the water maze experiment is that the animal has a greater motivation to escape from the water environment. And there is no need to fast, which is especially suitable for the testing of elderly animals. In addition, it is particularly sensitive to memory impairment caused by aging. Therefore, the water maze is most commonly used for the study of memory in elderly animals. 2. In the case of mice, in addition to the size of the swimming pool being about 50% of the rat, the platform diameter is also small (7.5 cm). The experimental method is similar to rats, but the training period is shorter. The general acquired training is 16 trainings in 3 days (4 on the first day and 6 on each of the next two days; the interval between the two trainings is 5 ~ 10min, the fourth day is the exploratory training, and the fifth and sixth days are the alignment Training, training six times a day, on the seventh day for the second exploratory training. 3. If observed with the naked eye, during all tests, the test is always sitting in the same position, about 60cm from the closest edge of the swimming pool. 4. Test at a fixed time every day. Operate gently and avoid unnecessary stress. 5. When comparing with other similar experiments, we should pay attention to the influence of various factors such as the sex of the animal, the strain, the size of the swimming pool, and the water temperature on the experimental results. In addition, when swimming speed is used as an observation index, it is necessary to take into account that the animal's weight, age, and skeletal muscle development status may affect the swimming speed. 6. When conducting experiments with elderly animals, it should be confirmed that the animals' swimming ability and visual acuity do not affect behavioral operations due to age. The method is as follows: expose the platform to the water so that the animal can see the platform. If the animal swims directly to the platform without difficulty after entering the pool, it means that the animal's swimming ability and vision are normal, and the experiment can be started. 7. Swimming is a large stress stimulus to animals, which can cause neuroendocrine changes. These changes may cause interference with the experimental results. For elderly animals, severe cases can induce cardiovascular disease and lead to stroke or even death. Therefore, if necessary, the animal can be placed in the swimming pool multiple times or the swimming time can be extended appropriately to increase the animal's adaptability to swimming. 8. When milk or milk powder is used to mix the water in the swimming pool, the water should be changed regularly to avoid spoilage;
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Morris water maze 
morris water maze --- behavior research method of learning and memory (1)