| Two experiments were conducted to test for possible differences between the parietal cortex (PC) and the hippocampal formation (HF) in the processing of egocentric (or personal) space and allocentric (or extrapersonal) space. In the first experiment, in order to test for allocentric spatial ability, rats with PC or HF lesions were given either no preoperative exposure or varying degrees of preoperative exposure to a cognitive mapping task, the Morris water maze. In the second experiment rats were given a test of egocentric localization, the Potegal task, which requires the animal to use a simple praxic turning rule.; The results from the Morris cognitive mapping task indicate that both HF and PC play an important role in the processing of place information. Both lesion groups suffered an impairment in this maze. However, in most conditions, the impairment of the PC group was as bad as or worse than that of the HF group, suggesting a more severe impairment in the PC group.; Furthermore, in all conditions, and especially in the retention conditions, the HF lesioned animals tended to employ praxic and taxic strategies to locate the platform. The PC animals also used such strategies, but to a lesser degree and with much less consistency than did the HF animals. The use of these alternate strategies for solving the Morris task by the lesioned animals draws attention to the need for researchers to be sensitive to the possibility that any given task may be solvable by a variety of strategies and that organisms may resort to these alternate strategies following brain damage. The animals' performance in the task, as determined by the particular dependent measures examined, may be either better or worse than would otherwise be the case were the task not solvable by the use of the alternate strategies. In such instances, the interpretation of the particular dependent measures used may be difficult.; Neither lesion led to impaired performance on the egocentric task. |
