Barnes Labyrinth--A Behavioral Research Method for Learning and Memory (4)

Barnes maze (Barnes maze) is a model used by American scholar Carol A Barnes in 1979 to detect the spatial memory of animals. Similar to the water maze and the eight-arm maze, the Barnes maze was built using rodents' dark-loving and inquiring nature. The enhancement that the animal gains is to escape from a bright, open platform into a dark, narrow box below the platform. This box is called the target box. After training, the animal learns and remembers the location of the target box. This model is less stressful to animals and neither fasts like an eight-armed maze nor is as stressful as a water maze. Therefore, it is more commonly used in memory research. Especially suitable for stress-related memory research and behavioral phenotype research of gene knockout mice.

(1) Experimental equipment Barnes maze produced by different manufacturers

It's about the same. Here we introduce the Barnes maze developed by Shanghai Xinsoft Information Technology Co., Ltd. It is a circular platform made of medical organic board, which can rotate and has a diameter of 122cm. There are 18 or 40 equidistant circular holes around the platform for rats and mice; the diameter of the holes is 10cm and 5cm, respectively. One of the holes (called the target hole) is connected to a dark box (that is, the target box). The other round holes are hollow and are not connected to any objects. The dark box is set in a drawer type, which is convenient for taking out animals from it. The target box is invisible from the surface of the platform. The maze is raised by 140cm. Animals can escape into the target box through the target hole. There are different considerations for the setting of mouse Barnes maze. For example, some shorten the diameter of the maze (such as 88 cm), the number of holes also decreases (such as 12), and the diameter of the hole is equivalent to the above. It is believed that such a setting is beneficial to increase the mouse acquisition ratio. But no matter which setting is used, the experimental operation is similar. Through training, the animal obtains the spatial positioning of the target hole.

(2) Experimental method

1. The day before the start of the experiment, the animals were individually placed in the target box from the target hole for 4 minutes.

2. Place the animal in a plastic drum (diameter 20cm, height 27cm) in the center of the maze to restrict movement for 5s.

3. Remove the drum and start the timer. The experimenter observes after blocking the curtain. When all the limbs of the animal enter the target box, it is counted as one escape, and the animal is allowed to stay in the box for 30s. Each animal was observed for a maximum of 4 minutes at a time. During this period, if the animal still cannot find the target box, remove the animal from the maze, put it in the target box and stay for 30 seconds. Use this gap to clean the maze. Animals are trained twice a day for 5-6 days.

4. Starting from the second training, before each training, the labyrinth is randomly rotated by one to several holes, but the target box is always fixed in the same orientation. The purpose of this is to prevent animals from relying on smell rather than memory to determine the location of the target hole.

The experiment records the following parameters: the incubation period of exploring any hole, the incubation period of reaching the target box, and the number of errors per animal (a single error is defined as the animal extending its head to or exploring any non-target hole, including focusing on exploring the same non-target hole ).

(3) Matters needing attention

1. Animal memory is weakened, mainly because the number of errors before the animal successfully obtains an escape is greater than that of the control group, and the latency period to reach the target box is extended; the latency period to explore any hole can be extended or there is no obvious change. Memory enhancement is the opposite, that is, the number of errors is reduced, and the latency to reach the target box is shortened.

2. The smell of animals left in the maze has a great influence on the next animal's maze operation. Therefore, in addition to rotating the maze between training sessions, it is necessary to clean the maze with 70% alcohol to eliminate the guiding effect of residual odor on the next animal.

3. The Barnes Labyrinth platform is similar to a large open field. Any factor (such as drug treatment or genetic modification) that affects the behavior of the open box (spontaneous activity) can affect the experimental results.

4. Strain differences The characteristics of the mice's love exploration make them ideal animals for Barnes' maze research, but the behavior of mice of different strains in this experiment varies greatly. For example, 129S6 mice rarely explore behavior in the Barnes maze, making it difficult to find the target hole. The C57BL / 6J mice have quite a lot of exploration behaviors, which is suitable for the Barnes maze experiment. This is especially important in the memory research of genetically modified mice.

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