The Barnes maze is a tool used in psychological laboratory experiments to measure spatial learning and memory

Memory

In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

. The test subjects are usually rodents such as mice or lab rats, which either serve as a control

Scientific control

Scientific control allows for comparisons of concepts. It is a part of the scientific method. Scientific control is often used in discussion of natural experiments. For instance, during drug testing, scientists will try to control two groups to keep them as identical and normal as possible, then...

 or may have some genetic

Genetics

Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

variable or deficiency present in them which will cause them to react differently to the maze.

Set-up

The Barnes maze consists of a circular table with 20 circular holes around the circumference of the table. Under each hole is a slot for a box, called the drop box. The goal of the maze is to reach the drop box, which is a box that has an open top, and can be reached through one of the holes in the top of the table. Exposure on the surface of the table serves as negative reinforcement, motivating the test subject to seek shelter. The only shelter available is the drop box, to which the test subject must flee. In order to accustom the test subject to the maze, it is guided into the drop box by a sheltering hand. After four to five runs, a normal test subject can quickly make a beeline for the drop hole. Fixed visual cues set up around the platform serve to orient the rodent during the trials.

Performance

Performance is typically measured by number of errors the rodent makes, i.e. the number of times it pokes its nose into, or hovers its head over a circular hole that does not contain the drop box. The rate of decline in the number of errors/trial is measured across subjects. Other performance values can also be measured, for example the strategy used by each rodent can be scored as random (randomly checking each hole), systematic (checking each hole in a pattern) or spatial (direct movement to the hole with the drop box).
An experiment done on Octodon degus reveaaled that spatial navigation is influenced by gender differences in nocturnal rodent species. A 16 months old male and female were tested using the Barnes circular maze.In the first ten days, the acquisition sessions of the rodents were 4minutes long everyday. After seven days, a retention test was performed. The acquisition session consisted of four daily 4min trials, during 10 days. Seven days later, the retention test was performed. To avoid the effect of hormonal fluctuation on spatial navigation, both the acquisition and the retention tests, were performed in 21-day regular cycling females in a period that corresponds to the diestrus phase of the estrus cycle. At the beginning of the acquisition, female degus were significantly slower than males to find the escape hole, but the situation reversed afterwards. Moreover, during the course of acquisition, females made significantly less reference memory errors, working memory errors as well as omission errors, than males. In both sexes, motivation and learning ceiling effects were reached at days 5–6 of the training. During the acquisition, females used more frequently a spatial strategy, while males preferably applied either serial, random or opposite strategies. The observed cognitive differences between male and female O. degus existed only during the acquisition period but not during the retention, indicating that acquisition and consolidation are differently influenced by gender (Popovic,Natalija, 2010).

Problems

One problem with the Barnes maze is the constant need to clean up after each trial. When nervous, most rodents will urinate and defecate on the table, necessitating the experimenter to clean up the entire table with disinfectant. Also, other animals who have not yet been tested cannot be allowed to witness the experiment in action, or they will have prior knowledge to the nature of the experiment, which will allow them to find the drop box more easily. Another consequence of untested animals witnessing the experiment is pre-experiment nervousness, which will make the animals experience more stress, and will make it harder for the experimenter to take hold of the animal. All of this shows a high level of comprehension in the animals of what is happening or will eventually be happening to them in the future.
Also, the use of vivid lights can also instigate a slight drawback if a video camera, computer and tracking software are used to document performance; most tracking methods are extremely sensitive to light reflections from the lit surface.

Barnes maze test

The Barnes maze consisted of a circular platform 160cm in diameter raised 75cm from the ground and surrounded with 45cm high wall. The platform was made of white plexiglas. Eighteen circular holes (8cm in diameter), were bored through the platform equidistant from each other (16cm), and 5.5cm from the outer edge. All holes except the target one were blocked with mesh. A plastic transparent escape box (31cm long×16cm wide×13cm high), was positioned under the escape hole. The start box was a white, open-ended cylinder (20cm in diameter and 15cm high, easily lifted from the platform to the roof, approximately 3m above. The maze was positioned in a room with many extra-maze cues (e.g., geometric figures, pictures, cage racks, furniture, etc.) to permit orientation of degus. The testing room was illuminated by fluorescent lights located on the ceiling (normal room lighting) such that the platform was exposed to uniform illumination of 210lx. A web camera was secured on the roof, directly above and focused on the maze surface, and plugged directly into the data acquisition computer. This allowed the experimenter while seated outside of the field of view of degus, to raise the start box, and immediately begin recording of its behaviour.

Statistical analysis

To avoid possible differences in motivation to perform the Barnes maze test, animals that failed to escape over 25% of trials for 3 consecutive days of training, were excluded. The data of the remaining six males and eight females were eventually used for statistical analysis.

The data are presented as mean±standard error of the mean (S.E.M.). The statistical analysis was made using the SPSS 15.0 statistical package. The data from acquisition of the Barnes maze were analyzed with the General Linear Model repeated measures analysis. If the repeated measures analysis showed significant differences between groups, post hoc analyses were performed at individual time points using the two-tailed Student's t-test for independent samples. The data from the retention day of the Barnes maze were analyzed by two-tailed Student's t-test for independent samples while a two-tailed Student's t-test for paired-samples was used to compare the data of the last acquisition day with those of the retention day. Differences were considered statistically significant if p<0.05.