The RAM task offers a variety of experimental advantages for the study of cognitive function in rodents. For example, its behavioral substrates and its temporal dynamics are now well characterized. The task assesses working memory and is sensitive to parametric manipulations which vary the demand on memory processes. Furthermore, there is an extensive literature regarding the brain areas and neurotransmitter systems that are critical for its performance. The RAM has been successfully used to study normal cognition in rodents and the changes in spatial memory that result from age, circumscribed lesions, and pharmacological manipulation of transmitter systems.
Like any useful tool, the RAM is best suited to address specific questions and problems. The co-authors of this chapter utilize the RAM to elaborate the neural substrates of spatial memory and to develop new therapies to treat the cognitive deficits associated with AD. To maximize the utility of the RAM, investigators must be aware of the inherent advantages and limitations of using this task within the context of specific paradigms. Some of these are enumerated below.
Advantages — Performance in radial mazes is based on natural foraging behaviors of rats and therefore generalization of results to the behavioral repertoire of the animal may be more accurate than those based on non-natural behaviors. Once animals have been trained to a baseline criterion, the task requirements can be changed for each session, thereby allowing the use of within-subject designs. This reduces the number of animals required for experiments. As has been indicated above, working memory can be selectively studied using the radial maze. Due to the relatively short testing duration which includes both an information acquisition and an information retrieval session, state-dependent effects are minimized when using radial maze tasks. Finally, the task is sensitive to cognitive alterations induced by drugs, lesions, genetic manipulations, and aging.
Disadvantages — Since the task is appetitively motivated, food restriction regimens are required that contrast with cognitive tasks which are aversively motivated. Some practical limitations include the need for intensive labor, extensive time, and sufficient space. For example, the majority of studies using the radial maze are done on well-trained animals and extensive training is required to establish stable baseline performance.
Overall, the radial maze is an excellent choice for providing insights regarding memory processing. It can be used: (1) to examine the anatomical, biochemical, and molecular substrates of memory; (2) to develop models of cognitive disorders such as AD; and (3) to evaluate new and innovative therapies for the treatment of cognitive dysfunction. It is a powerful behavioral tool that can address a multitude of hypothesis-driven questions about the complexity and dynamics of memory, its underlying biology, and its attendant diseases.
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