Meeting Abstract
Sex differences in brain and behavior are well documented in many species. Conventional thought is that sex differences are associated with polygamous males, which are better at spatial memory because sexual selective pressure has promoted mate searching in males. Monogamous species are not expected to differ in spatial ability, or the mechanisms associated with promoting spatial memory, presumably because the selective pressures on males and females is relatively equal. However, sex-specific selection is not identical in intensity and therefore should apply powerful influence over neural and behavioral phenotype in monogamous animals. We hypothesize that sex-specific cognitive demands are present in monogamous species. The effects of these demands should be observable in spatial learning performance and neural structures associated with spatial learning and memory. To this end, we analyzed spatial memory performance, hippocampal volume, and hippocampal oxytocin receptor (OTR) expression. The hippocampus is synonymous with spatial memory; our focus on OTR is rooted in its role for modulating memory and because it is well expressed in the hippocampus. To assess these parameters, we used a sexually monomorphic, socially monogamous rodent – the prairie vole (Microtus ochrogaster). Our results showed that males learn faster and perform better in a spatial memory test compared to females. Consistent with previous work, we found no sex difference in hippocampal volume. However, OTR expression in males was significantly lower than females. This is the first evidence implicating hippocampal OTR density in modulating spatial memory performance.
