The Barnes maze is a widely used apparatus for learning and memory.
- Comes with 1 target box
- Additional holes can be created upon request.
- The entire top can be rotated around the central partition. Separately, the dark escape box can be rotated underneath the table. The escape box can be removed from a holder for easy cleaning
- A false floor modification can be requested. This functions as second table that rotates alongside the target box, closing the floors not located at the escape box
- The top is thick acrylic available in white, grey, or blue, designed with enough thickness to prevent visual cues of the target box
The Barnes Maze is a commonly used behavioral task in neuroscience for studying spatial learning and memory. This test is based on the fact that avoiding exposed and brightly lit areas is an essential survival strategy for rodents. It was observed that rodents have a remarkable ability to remember spatial locations, especially when motivated to escape, and this has been adapted into a behavioral task. The maze consists of a circular platform lined with holes around the perimeter, one of which leads to an enclosed escape chamber. The animal will use intra- and extra-maze cues to quickly learn the location of the target hole allowing them to escape. This task requires use of hippocampal-dependent spatial reference memory, and this ability to remember the location of the target hole can be effected by the administration of certain drugs or in disease models.
Carol Barnes first developed this maze for evaluating spatial learning and memory in 1979 (Barnes 1979). It was initially intended for rats, but has become increasingly popular for mice as well (Sunyer et al. 2007). In the battery of tasks used to measure spatial learning, the Barnes Maze is commonly compared to the Morris Water Maze and the Radial Arm Maze, and is generally considered less stressful than these alternatives (Harrison et al. 2006). Since its initial use, the Barnes Maze has been used to study the cognitive ability of animals with various deficits, such as mutant lines, hippocampal lesions, and Alzheimer’s disease (Harrison et al. 2006, Attar et al. 2013).
The apparatus used for the Barnes Maze consists of raised circular platform, ranging from 50-100 cm in diameter to accommodate mice, rats, and small primates, with 12, 18, or 20 holes equally spaced around the perimeter. Each hole is large enough to allow the animal to pass through and the holes are positioned several centimeters from the edge of the maze. One of the holes is designated the target hole and leads to a small, dark recessed chamber beneath the maze platform. It is important that the escape chamber is not visible to the animals from the platform. The entire platform is able to rotate around the center point, with the escape chamber able to rotate to different holes beneath the maze. The platform of the maze is colored to provide contrast with the color of the animals tested. The entire apparatus is raised approximately 100 cm from the floor.
The holes of the maze are numbered starting from the target hole; the holes to the right of the target hole are numbered starting with +1, and those to the left are numbered starting with -1, with an opposite hole directly across from the target hole.
Visual cues can be prepared using different colors and shapes and can be placed surrounding the maze. These, along with visual cues within the testing room, will serve as the animal’s reference points while performing the maze task.
The maze should be brightly lit from above to allow animals to see extra-maze cues in the testing room and will encourage animals to seek the dark recessed chamber.
A mounted video camera is used to record the experiments from above the maze. Tracking software can be used to follow the moments of the animals within the maze. Live scoring can also be performed with a stopwatch.
The purpose of the Barnes Maze is to assess spatial memory and learning in animals, in a control vs. disease model/treatment group, by observing their ability to remember the location of the target hole leading to an enclosed escape chamber. This test can provide information regarding hippocampal-dependent learning, specifically spatial memory. For example, the effects on memory abilities in animal models of aging or neurodegenerative diseases can be tested using the Barnes Maze. Typically animals are capable of learning and remembering the location of the target hole using intra- and extra-maze cues. This aptitude to remember decreases, and the number of errors increases, in animals with impaired neurocognitive abilities.
Pre-Training for the Barnes Maze
Prior to testing, animals need to be familiarized with the maze and the location of the escape chamber. Prepare visual cues surrounding the maze and leave them in place for all training and testing trials. Place the animal in the center of the maze and then gently guide it to the hole leading to the escape chamber. Forcing the animal into the chamber may be too stressful, so instead allow the animal to enter on its own. Allow the animal to remain in the chamber for at least two minutes.
Evaluation of Spatial Memory Using the Barnes Maze
Prepare the apparatus by cleaning it to remove olfactory cues from previous runs. Rotate the maze to control for remaining olfactory cues and adjust the escape chamber so that it is in the same position. Turn on the camera. Place the animal in the center of the maze and allow it to explore the maze for three minutes. Record the number of errors the animal makes and the latency time. An error occurs when the animal pokes its head into a hole that is not the target hole, and the latency time is the time it takes the animal to locate the target hole. End the trial when the animal enters the escape chamber or after three minutes have elapsed. If the animal does not reach the escape chamber, gently guide it to the target hole, allow it to enter the chamber and remain there for one minute. Return the animal to its home cage until the next trial. Each animal should perform four trials on each of four testing days with approximately fifteen minutes between each trial.
Evaluation of Reference Memory Using the Barnes Maze
On the fifth testing day, prepare the apparatus and close the target hole or remove the escape chamber. Clean the maze and rotate the platform. Turn on the camera. Place the animal in the center of maze and allow it to explore for ninety seconds. Record the number of errors the animal makes and the latency time. Remove the animal after the ninety seconds have elapsed. Repeat this procedure seven days later on the twelfth day.
Since its original design, the Barnes Maze has been adapted with several simple modifications. For example, a curtain surrounding the maze platform can be used to prevent the animals from making spatial associations between distal room cues and the location of the target hole (Harrison et al. 2006, Rosenfeld & Ferguson 2014). The escape chamber beneath the maze can optionally lead to an escape tube that allows the animal to reach a home cage or other safe cage (Rosenfeld & Ferguson 2014). A false floor can also be added beneath the maze platform to close off the holes that do not lead to the escape chamber.
The data obtained from the Barnes Maze generally consists of two main measures: the number of error head pokes the animal makes and the time it takes the animal to enter the target hole and escape chamber. Other measures such as the total path length and movement speed can be measured and obtained by tracking software. As the animal learns the relationship between local or distal spatial cues and the location of the target hole, the number of error head pokes and the latency time should decrease. These measures can be simply graphed and compared across a sham control group and a disease model, as shown in the graphs below:
The search strategy used by the animal must be analyzed manually using the video recording and tracking software. Generally, one of three search strategies is used by the animal to locate the target hole:
- Direct – the animal moves directly to the target hole or an immediately adjacent hole before entering the target hole
- Mixed – the animal searches random holes, crossing through the center of the maze
- Serial – the animal visits several adjacent holes in a clockwise or counter-clockwise manner before reaching the target hole
To help visualize these strategies, the exact position of each head poke error can also be counted and graphed, as shown below:
Using graphs similar to these to compare latency time, number of error head pokes, the position of these errors, and the total path length between different disease or treatment groups allows for easy visualization of the effect on spatial memory and learning. Animals in the control groups should show significant improvements in reaching the target hole quickly and efficiently. Animals as disease models of neurodegenerative disorders, for example, should show a much slower learning curve with more errors and longer path lengths, even after several days. Generally, animal cohorts of 10-30 animals are sufficient to obtain p-values of <0.05 using ANOVA and step-down Bonferroni tests (Harrison et al. 2006, Attar et al. 2013, Sunyer et al. 2007).
A major strength of the Barnes Maze is the minimal stress placed on the animals. The Barnes Maze is considered to be a less anxiogenic alternative to the Morris Water Maze. The Morris Water Maze subjects the animal to significantly more stress as it must be submerged in water, swim in order to survive, and search for the escape platform (Hodges 1996, Harrison et al. 2006). However, some groups report that there is little difference in stress and anxiety between the two mazes (Harrison et al. 2006). While the Barnes Maze is thought to produce less anxiety, some stimulation must be used, such as bright lighting or adverse noise, to encourage the animals to escape the open platform and this can induce some level of stress. The Radial Arm Maze is also commonly used to test spatial learning and memory, and this task is also considered less stressful than the Morris Water Maze. The absence of significant stressors allow for better observations of working and reference memory in the animals as they perform in the maze.
As with all mazes that measure aspects of learning and memory, it is important to remember that many different processes play into behavior in the maze. Factors such as anxiety and exploratory activity should be considered when interpreting the results of a spatial memory task.
- The Barnes Maze is a commonly used maze to test spatial learning and memory, and is a less stressful alternative to the Morris Water Maze
- This task asks animals to escape a brightly lit open platform by remembering the location of a hole leading to an enclosed chamber
- Intra- and extra-maze cues can be used to aid the animals in remembering the location of the target hole; alternatively, the absence of cues will make the task more difficult
- Animals in control groups show rapid learning as they remember the location of the target hole, while in comparison, animals as disease models of neurodegenerative disorders show a much slower learning curve