0108 Spatial Memory and Navigation Performance Across the Menstrual Cycle

Abstract Introduction Some studies have reported that the menstrual cycle and fluctuating sex hormones influence sleep microarchitecture, which may in turn shape sleep-dependent memory processes. We examined within-person menstrual cycle dynamics on spatial memory and navigation performance. The Minecraft Memory and Navigation (MMN) task was administered to participants during four distinct menstrual phases: menses, late follicular, midluteal (ML), and late luteal. Our goal was to determine whether variations in sex hormones and sleep spindles across the cycle predicted changes in spatial memory and navigation performance. Methods Forty-three reproductive-aged female participants (18–35yrs) completed the MMN task four times, once per menstrual phase. During training, participants learned the locations of 12 objects across two training trials. Immediate pre-sleep and delayed post-sleep recall were tested by being teleported to random points in the environment and then navigating to remembered object-locations and placing the objects. Training analyses evaluated environment exploration, measured as the area of the environment covered while searching for objects. MNN test analyses examined spatial memory accuracy (Euclidean distance between true and indicated object-locations), navigation metrics (area explored and total steps), and we evaluated sigma power (12-15Hz). All within-subject variables were z-transformed and linear models fit. Results We found menstrual cycle effects on navigation, with participants in the ML, compared to other phases, spending more time during the exploration period (p=0.02), but showing worse spatial memory accuracy for the objects at immediate recall (p=0.018). However, overnight changes in navigation performance or spatial memory did not vary by menstrual cycle phase. A main effect of parietal sigma activity (12–15Hz) predicted greater overnight spatial memory accuracy improvement (p=0.034). Conclusion During the high-hormone ML phase, participants showed more exploratory navigation during learning but performed worse on the immediate pre-sleep test, which could reflect broader spatial search ability and challenges to retain specific spatial locations. We also found that sigma power was associated with overnight spatial memory performance gains, but not overnight changes in navigation behaviors. Despite the role of spindles in overnight spatial memory improvement on this real-world, immersive spatial navigation task, we did not find that the menstrual cycle modulated these sleep-dependent memory processes. Support (if any) RF1AG061355 (Baker/Mednick) K08HD107161 (Simon)