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Sketchpad Series

Changes in hippocampal structure and spatial memory performance associated with rise and fall in estradiol across the menstrual cycle

Poster Session C - Sunday, March 30, 2025, 5:00 – 7:00 pm EDT, Back Bay Ballroom/Republic Ballroom

Hillary Schwarb¹ (hschwarb2@unl.edu), Aaron T. Anderson², Bradley P. Sutton², Graham R. Huesmann², Neal J. Cohen², Ana M. Daugherty⁴, Curtis L. Johnson³; ¹University of Nebraska-Lincoln, ²University of Illinois at Urbana-Champagin, ³University of Delaware, ⁴Wayne State University

Decades of preclinical research have identified differences in hippocampal structure as sex-hormones shift across the estrous cycle. Indeed, when estradiol is high, dendritic spine density increases as much as 30% compared to when estradiol is low. Human studies investigating hippocampal volume changes across the menstrual cycle have been equivocal. Volume, however, is a gross measure of tissue composition and perhaps not sufficiently sensitive to identify subtle, hormone-related changes. Magnetic resonance elastography (MRE), an emerging imaging tool, is sensitive to microstructural alterations in brain tissue. We hypothesized that tissue viscoelasticity, an MRE-derived measure of microstructural organization, would be more sensitive than volume and show measureable changes as estradiol fluctuates. In this study, natural-cycling women were tested twice: At the start of menses (low estradiol) and just before ovulation (peak estradiol). At each testing session, participants completed a blood draw to confirm estradiol levels, an MRI/MRE scan, and the virtual Moris Water Maze task. Preliminary data (N=10) indicate that while hippocampal volume did not differ when estradiol was high vs. low, MRE-derived measures of hippocampal viscoelasticity did significantly differ such that hippocampal organization was greater when estradiol was high. Furthermore, Morris Water Maze task performance significantly differed such that participants traveled shorter distances to find the hidden platform (indicative of better memory) when estradiol was low compared to when estradiol was high. In the age of precision medicine and individual differences in structure-function relationships, it is essential that we acknowledge and account for hormonal shifts that may well contribute to these relationships.

Topic Area: LONG-TERM MEMORY: Episodic