Factors contributing to sexually dimorphic performance on the Morris water task.

Abstract

Sex differences in place learning on the Morris water task were examined in this dissertation. Adult Long Evans hooded rats were tested on this task to determine whether there are sex differences on this task, whether males and females use different strategies to solve the task, whether they attend to different aspects of the environment for navigation, as has been previously hypothesized, and whether they both use the fornix (hippocampal formation) for navigation on this task. Exploratory behaviors were also examined for both sexes to establish whether there was evidence that they engage in different activities while forming a cognitive map. Lastly, the role of the female estrous cycle on water maze performance was examined. Results indicated that males and females are equally impaired following fornix lesions, and there is no evidence that they use different strategies to solve the task or attend to different aspects of the environment. There was an overall sex difference in performance on the task, with males solving the task faster than females, and searching the target area at a much higher rate than females. There was some preliminary evidence of sex differences in exploration which predicted place learning in the water maze. Lastly, the estrous cycle did significantly effect the female's performance. Females in the high estrogen period were generally less efficient on the task than those in the low estrogen phase. This was interpreted to reflect a difference in motivation across the days of the cycle, rather than a difference in ability to perform the task.