Morris water maze experimental criteria, research progress of morris water maze experiment

----- Statistical Methodology Guidelines

The incubation period is the measurement data, and the variance analysis can be used. However, the homogeneity test of variance is first performed according to the procedure of analysis of variance. The variance is calculated, the F value is calculated, and the comparison method is used to compare the averages of multiple experimental groups and one control group. Perform appropriate variable conversion on non-normal or variance data. After the normal or variance requirements are met, the converted data is used for statistics; if the variable has not yet reached the normal or variance, Use the rank sum test to perform statistics. Counting data, such as the number of crossing stations, can be tested by X2. If the total number of four-grid tables is less than 40, or the total number of cases is equal to or greater than 40, but the theoretical number is equal to or less than 1, the exact probability method should be used instead.

Morris   The experimental data of the water maze is more complicated, and its statistical analysis is also more difficult. In particular, there are many problems in the statistical analysis of the escape latency measured by the rats in the search for hidden platform tests. In the past studies, some domestic literatures directly calculated the average escape latency of each day and then performed t-test or analysis of variance, or according to the escape latency of rats, the stability was stabilized 3 days after the navigation test, only for the last 3 days. The average escape latency was analyzed by t test or analysis of variance. Some studies conducted a one-way analysis of variance for the escape latency of 1 to 5 days. We believe that the above statistical methods are not correct. A more obvious error is that the average escape latency of the last 3 days of stabilization tends to represent the memory level. The first problem encountered is that the rats in the physiological state only show this, while the experimental memory impairment group tends to be 3 days later. The escape latency has continued to decline. The escape latency of normal young and early-aged rats tended to be stable in the last 3 days, but the escape latency of rats in experimental injury group was higher due to learning and memory impairment, and the escape latency was still decreasing on the 3rd to 5th day. It does not tend to be as stable as the normal control group. Not only that, but also the above statistical methods for the misunderstanding of the statistical characteristics of the escape latency data measured in the hidden platform test. The escape latency in the hidden platform test has the following characteristics: 1 series repeated measurement design, that is, data obtained by repeated measurement from the same subject at different time points after giving a certain treatment (evacuation latency); There are at least several effect factors such as animal group and detection time point in the statistical analysis of the incubation period (independent variable), and there are interaction effects between the effect factors; 3 the height of the escape latency measured at different time points of the same subject animal Autocorrelation; 4 there is truncated data (maximum latency). Accordingly, the escape latency of the hidden platform test in the Morris water maze should be based on the multivariate analysis of variance of the repeated measures data of variance (ANOVA) combined with the survival analysis method of the censored data, which is commonly used in foreign literature reports. The method further analyzes the mean value of the latency, with the number of days as the independent variable, the incubation period or the swimming speed as the dependent variable.

The morris water maze experiment was established in 1981 by American scientist Richard GM Morris. Originally used to study the regulation of brain structure on learning and memory, and later gradually developed into the most commonly used model for evaluating animal learning and memory. The basis of the morris water maze experiment is that rodents have a strong motivation to escape from the water in the water and escape the water environment in the quickest and most direct way. The process of learning to escape the water environment reflects the animal's ability to learn; spatial positioning according to the surrounding environment, purposefully swimming to a safe place (platform) in the water, reflecting the animal's spatial memory ability.

1. In contrast to food-driven models (such as the radial arm maze), the biggest advantage of the water maze experiment is that animals have greater motivation to escape the water environment. And no need to fast, especially suitable for testing of older animals. Plus it is particularly sensitive to memory loss caused by aging, so water maze is most commonly used in the study of memory in older animals.

2. For example, in the case of mice, the diameter of the platform is also small (7.5 cm) except that the size of the swimming pool is about 50% of that of the rat. The experimental method is similar to that of the rat, but the training period is shorter. General acquired training for 16 days in 3 days (4 times on the first day, 6 times a day in the next two days; interval between the two trainings is 5~10min, the fourth day is the exploration training, and the fifth and sixth days are the alignment) Training, training six times a day, the seventh day for the second exploration training.

3. If observed with the naked eye, the test is always sitting in the same position during all tests, about 60 cm from the nearest edge of the pool.

4. Test at fixed time every day. The operation is gentle and avoids unnecessary stress irritation.

5. When compared with other similar experiments, it is necessary to note the effects of various factors such as animal sex, strain, pool size and water temperature on the experimental results. In addition, when swimming speed is used as an observation index, it is necessary to consider the weight, age, and skeletal muscle development of the animal, which may affect the swimming speed.

6. When conducting experiments with elderly animals, it should be confirmed that the swimming ability and visual acuity of the animals do not affect the behavioral operation due to the increase in age. The method is as follows: the platform is exposed to the water surface to enable the animal to see the platform. After the animals are placed in the pool, they can swim directly to the platform without any difficulty, indicating that the animal's swimming ability and vision are normal, and the experiment can be started.

7. Swimming is a large stress stimulus for animals that can cause neuroendocrine changes. These changes may interfere with the experimental results. In older animals, cardiovascular disease can be induced in severe cases, leading to stroke or even death. Therefore, if necessary, the animal can be placed in the pool multiple times or the swimming time can be appropriately extended to increase the animal's ability to adapt to swimming.

8. When using water or milk powder to stir the water in the pool, change the water regularly to prevent the water from spoiling.