Over the past five decades spatial behavior has been a subject of research interest in psychology and neuroscience, in part based on philosophical theories of mental spatial representations. In order to continue uncovering the facts regarding spatial behavior, the focus of this thesis was on the contribution of entry point and visual inputs to the organization of exploratory locomotion and spatial representation in the rat. Despite the contribution of the hippocampus to spatial abilities, the exploratory locomotion is still visually organized in rats with damage to the hippocampus. On the other hand, recent studies have demonstrated a contribution of visual areas to the spatial ability of the rat. Nevertheless, the contribution of visual cortex to the organization of exploratory locomotion has not been studied in an open field. The experiments in this thesis were designed to characterize the organization of exploratory locomotion to the point of entry and/or visual cues. Rats were started from the edge or center of an open table near or on which a salient object could be placed. The main findings were that rats organized their exploratory locomotion to their point of entry and modified their behavior as they encountered objects. Also, rats with damage to visual cortex displayed an extra-attachment to the visual objects and in contrast to controls did not expand their exploratory locomotion with time. The results are discussed with respect to the centrality of the entry point in the organization of exploratory locomotion and the neural network that control visual exploration in the rat. / xiii, 220 leaves : ill. ; 29 cm. --

The thesis examines the ability of animals to construct a home base. The home base is a point in space where animals rear, groom, and circle and is a primary element in organized spatial behaviour (Eilam and Golani 1989). Once animals establish a home base, they make outward trips and stops, and after a series of trips and stops they return again to the home base. The home base behaviour of animals acts as a platform for asking questions about the cognitive organization of an environment. The thesis describes five main findings. Control and hippocampectomized animals use (1) proximal and (2) distal cues to form a home base and organize their behaviour. (3) Control and olfactory bulbectomized animals form home bases in the dark where as hippocampectomized animals are impaired suggesting self-movement but not olfactory cues play a role in home base behaviour. A final set of experiments demonstrated that control and hippocampectomized animals learn the position of (4) proximal and (5) distal cues so that in the cue's absence, animals still form a home base at that position. The demonstration that a central feature of exploratory behaviour, establishing a home base, is preserved in hippocampectomized rats in relation to proximal, distal, and conditioned visual cues - reveals that exploratory behaviour remains organized after hippocampal lesions. The inability of hippocampectomized rats to form a virtual home base in the absence of visual cues is discussed in relation to the idea that the hippocampus contributes to inertial behaviour that may be dependent upon self-movement cues. / xv, 232 leaves : ill. ; 29 cm.

Stress-related cognitive changes are still a matter of debate. In some particular neuropathological conditions such as focal ischemia, cognitive functions have been shown to be significantly impaired. These conditions, however, may be improved by some factors such as steroid hormones. The purpose of the current thesis was to assess the structural and functional effects of corticosterone-related experiences on the hippocampus before and after endothelin-1 (ET-1)-induced stroke. We found corticosterone-related experiences enhance the hippocampal recovery, and improve its function in both wet and dryland tasks after ET-1-induced focal stroke. Structural and functional effects of such experiences prior to the focal ischemia in the hippocampus, however, showed that stress, not corticosterone is a strong inhibitor for hippocampal recovery. / xii, 252 leaves : ill. ; 29 cm. --