Sex differences in the ability of C57BL6/J mice to complete OSL has not been reported.

Mouse models of early-life brain injury are useful for studying injury to the hippocampus. At postnatal day 13 (P13), there are few methods that assess hippocampal function. At this developmental time point, a mouse’s eyes are still closed and they use olfaction to navigate their environment. The Olfactory Spatial Learning (OSL) paradigm tests whether mouse pups can create an olfactory spatial map to reach a goal containing their littermates.

Male and female naive mice were tested on the OSL paradigm at P13, in either a Fixed or an Altered condition. Each corner of the OSL chamber had a cotton swab containing a different scent. Each mouse completed four Training Trials where they could navigate the chamber until they found the goal petri dish containing littermates, or a maximum of 150 seconds. The mouse then completed one Test Trial where the petri dish was removed and the mouse had to navigate to the goal location of the removed petri dish.

Data passed Shapiro-Wilk test for normality. Mixed-effect analysis revealed significant difference in latency to goal across Training Trials (p<0.05), indicating that mice learn how to reach the goal faster across trials. On the Test Trial, male mice in the Fixed condition reached the goal location faster than male mice in the Altered condition (p<0.05), but this difference was not observed in female mice.

These data suggest that P13 male mice, but not female mice, exhibit olfactory-dependent spatial learning. This is the first demonstration of sex differences in hippocampal-dependent spatial learning at this young developmental timepoint. Future directions include using OSL to study sex differences in hippocampal function in mouse models of early life brain injury including perinatal hypoxia-ischemia.