Menstrual Cycle Brain Plasticity: Ultra-High Field 7 T MRI Reveals Changes in Human Medial Temporal Lobe Volume in Female Adults

Abstract Fluctuations in ovarian hormones influence the risk of depression and Alzheimer's disease, which is twice as high in females. How ovarian hormones affect brain structural plasticity in regions involved in memory and affective cognition, however, remains unclear. Detailed menstrual cycle phenotyping in health may therefore allow for differentiating early processes of cognitive decline from normal aging and offer insights into mechanisms contributing to dementia and depression. We performed longitudinal mapping of medial temporal lobe subregion morphology at 6 timepoints across the menstrual cycle in vivo using a dense-sampling protocol, ultra-high field neuroimaging and individually-derived segmentation analysis in 27 healthy participants (19-34 years). We found positive associations between estradiol and parahippocampal cortex volume, progesterone and subiculum and perirhinal Area 35 volumes, and an estradiol*progesterone interaction with CA1 volume. We confirmed volumetric changes were not driven by hormone-related water or blood-flow changes. We provide open access to the data and analytical pipeline. This resource provides a blueprint for examining shared dynamics of the brain and ovarian function to develop sex-specific strategies for identifying and treating brain disorders that affect memory and cognition.