UC Berkeley

Laboratory mice are the most commonly studied mammal today and they are frequently used as models of human disease. In the last decades, the mouse has become a popular model for understanding genes, brains and behavior. Therefore, it is of great importance that we develop a detailed understanding of the cognitive phenotype of the animal that we so frequently utilize in the laboratory. Sex differences are an important consideration in this phenotype. Sex differences in spatial behavior are seen in a number of species, suggesting a male advantage in all things spatial and a female advantage in object recognition memory. These data are consistent among humans and rats, but inconsistent in the mouse. The goals of this study were to discover whether mice would exhibit similar sex differences in a series of tasks designed to assess cue use at different spatial resolutions. The first experiment offers an assessment of cue use in a navigation task. Specifically looking at the use of geometry and large distal cues in the testing environment. The second experiment looks at the details of object recognition. The last experiment tests both object recognition and location memory, to look more closely at the nature of the sex difference with respect to proximal cues. We housed the mice in conditions that were more ethologically valid to allow a better comparison of our data to humans, as well as enriched laboratory animals and wild caught animals that must organize their behavior in much more complex environments than those provided in the lab. The navigation task revealed a male reliance on geometry and a female flexibility in the use of multiple sets of cues. The standard object recognition tasks all demonstrated a female advantage in discriminating the novel from the familiar object. Female mice distinguished novel from familiar objects when these objects had many similar features, while male mice only discriminated between them if the objects were unlike one another. Frequently, female mice also exhibited greater attention to the objects. The male mice demonstrated an advantage only when the change provided new directional information. The female mice displayed evidence of attention to the relationships between unique cues and the features encompassed within them. This is consistent with current literature on rats and humans and suggests that mice also exhibit sex difference in cue use strategies. This suggests that, with attention to ethologically valid housing and testing, mice are an appropriate model of mammalian behavior and cognition.