Sex and seasonal variation in hippocampal volume and neurogenesis in the eastern chipmunk, Tamias striatus

Abstract

The hippocampus (HPC) is important in spatial memory and navigation and also exhibits adult neurogenesis. In wild-living species, HPC volume and neurogenesis have been found to differ between the sexes and vary seasonally in tandem with spatial behaviours such as food-caching and mating. However, few studies have simultaneously compared across sex and season, and the literature contains inconsistencies. The present study examined sex and seasonal differences in HPC volume and neurogenesis in the eastern chipmunk, Tamias Striatus. HPC volume was greatest in males after controlling for age, consistent with males' greater spatial behaviour, but was seasonally stable. Neurogenesis exhibited a curvilinear pattern across the active season after controlling for age, with no sex or seasonal differences corresponding to the timing of spatial behaviours. The pattern of results was partially consistent with predictions based on chipmunk behavioural ecology, with some unexpected results, highlighting the importance of studies involving naturally variant populations.