Furthermore, rodents can learn that no punishment occurs if they do not enter the escape cage. The mildly aversive stimuli typically used in the Barnes maze ( i.e. bright lights), however, may not provide sufficient motivation for the rodent to locate the escape cage 45. In rodent models where water maze use is not possible, the Barnes maze may provide a fine-tuned assessment of spatial memory retention 31. Although water maze performance has been shown to be more sensitive to genetic alterations in mice 3,46,47, Barnes maze performance is more sensitive to certain other alterations 48,49. As a dry land maze, the Barnes maze may be more ethologically-relevant for terrestrial rodents 45. It is also commonly used for behavior phenotyping of various mouse strains 18-21, assessment of aging effects 7,22-28, and Alzheimer's Disease-related deficits in animal models 3,29-33, as well as the effects of exercise and dietary, environmental, and metabolic alterations 34-42.Ī primary advantage of Barnes maze use is that it induces less stress in the subjects relative to water mazes, such as the Morris water maze 43, although both can induce acute increases in plasma corticosterone concentrations in mice 44. In our labs, Barnes maze performance has been used as an index of neurotoxicity after developmental bisphenol A (BPA) or ethinyl estradiol (EE2) exposure 9-1113. Other species assessed using the Barnes maze include American cockroaches ( Periplaneta americana) 14, corn snakes ( Elaphe guttata guttata) 15, squamate reptiles ( e.g. side-blotched lizards ) 16, and nonhuman primates ( e.g. mouse lemurs ) 17. This maze has been used to test spatial navigational learning and memory in a wide range of rodent models, including rats ( Rattus norvegicus), mice ( Mus musculus), deer mice ( Peromyscus maniculatus bairdii), California mice ( Peromyscus californicus), and hystricomorph rodents ( e.g. degus ) 8-13. Here, we focus on the circular platform or Barnes maze, first described in 1979 by Dr. Several types of mazes have been developed as noninvasive assessments of this hippocampal-dependent spatial learning and memory in small and large rodents ( e.g. water maze, multiple T-maze, radial arm maze and dry-land mazes) 3-6. In contrast to working memory which refers to memory within a test session or trial, reference memory refers to memory across test sessions or trials and is more closely related to long-term memory.
Several decades later, a spatial reference memory system was proposed 2. Spatial learning and memory in laboratory rodents was first assessed with food-deprived rats that navigated a maze of alleyways to locate a food reinforcer 1. Even so, the Barnes maze is a widely employed behavioral assessment measuring spatial navigational abilities and their potential disruption by genetic, neurobehavioral manipulations, or drug/ toxicant exposure.
Both Barnes and water mazes can be time consuming as 4-7 test trials are typically required to detect improved learning and memory performance ( e.g. shorter latencies or path lengths to locate the escape platform or cage) and/or differences between experimental groups. Appropriate stimuli must be identified which motivate the rodent to locate the escape cage. For example, while extra-maze cues are effective for rats, smaller wild rodents may require intra-maze cues with a visual barrier around the maze. Barnes maze construction and testing methodologies can differ for small rodents, such as mice, and large rodents, such as rats. Type of search strategy ( i.e. random, serial, or direct) can be categorized as well.
From those video recordings, use of automated tracking software can generate a variety of endpoints that are similar to those produced in water mazes ( e.g. distance traveled, velocity/speed, time spent in the correct quadrant, time spent moving/resting, and confirmation of latency). Latency to locate the escape cage can be measured during the session however, additional endpoints typically require video recording. Mildly aversive stimuli ( e.g. bright overhead lights) provide motivation to locate the escape cage. All but one of the holes are false-bottomed or blind-ending, while one leads to an escape cage. Considered less stressful than water mazes, the Barnes maze is a relatively simple design of a circular platform top with several holes equally spaced around the perimeter edge. Improved performance over sessions or trials is thought to reflect learning and memory of the escape cage/platform location. Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land (Barnes) mazes.