| Most animals continuously navigate around the environment searching for food, mating partners, or a safe refuge. To accomplish these tasks successfully, navigation must be supported by learned strategies and constraints imposed by their perceptual and motor systems. This thesis examines how the habitual, stereotyped paths of foraging rats toward a goal, although initially influenced by their natural orientation toward visual landmarks and the use of path integration, set the stage for a flexible strategy in which route precision increases, memory demands decrease, and animals are better able to cope with unexpected environmental changes.;The literature on rodent navigation has typically emphasized the role of visual landmarks in supporting and guiding animals' search for a goal. However, when returning frequently to the same location, an animal might be expected to develop specific movement patterns, following the same succession of turns, or moving along the same areas of a terrain during different levels of illumination. The findings of this thesis suggest that after returning frequently to a location, guided initially by visual cues, animals soon develop paths that can be successfully followed in the absence of any visual (or olfactory) information.;What are the benefits of performing a habitual path? First, stereotyped routes are likely to increase the chances of recognizing landmarks along the way because the landmarks are memorized in a specific sequence. Second, stereotyped routes may decrease memory demands by reducing the need to store multiple views of landmarks, because they are increasingly likely to be encountered from the same location and point of view along the route. Third, if a predator is averted, learned routes might increase the chances of accurate escape, as the rodent is required to perform, but not to calculate, the route. Finally, habitual paths keep the organism within familiar terrain, likely decreasing the probabilities of chance encounters with unanticipated predators or other environmental risks. Learning of motor responses (or route following) is a demanding task; it requires repeated experience with the environment, and is built upon the initial orientation responses, but it supports rapid and accurate navigation as much as other navigational strategies. Careful and extensive examination of how route learning interacts with the use of visual landmarks is needed to explain how rats, as well as other species, perform successfully navigational tasks. |
