Abstract: Menopause is marked by a 90% decline in endogenous ovarian hormone
production. Among brain regions affected by this reproductive aging event
is the hippocampus (HC), which is responsible for encoding flexible and
efficient spatial navigation. In rodents, estradiol’s influence on HC
structure has been marked by changes in dendritic spine density and
ultimately changes in behavior in spatial navigation (Korol et al., 2004).
We aimed to bridge previous findings in animals to humans in the context of
reproductive aging. We collected high resolution structural HC scans and
collected blood samples from healthy midlife adults who were later tested
on a behavioral Dual-solution Paradigm (DSP), a task testing for navigation
strategy. For comparison, we also used our DSP to test navigation strategy
in a cohort of healthy young adults. We hypothesized that reductions in
estradiol levels in midlife women throughout reproductive aging would
result in a decrease in HC volume, which would ultimately shift women’s
strategies from using a flexible HC-mediated strategy to an
alternatively-mediated rigid strategy in the DSP task when compared to
younger adults. Results of this pilot study indicated no main effect of
reproductive stage on hippocampal subfield morphology and a main effect of
reproductive stage on spatial navigation strategy among our female cohort,
indicating a shift away from flexible navigation to heavily relying on
learned routes. By investigating the midlife period, further research could
delineate how earlier reproductive aging, as opposed to later chronological
aging, influences cognitive changes decades earlier in the aging process.