Functional connectivity density as a biomarker for Alzheimer's disease: Distinct neural mechanisms in young‐ and late‐onset subtypes

Our results reveal distinct FCD signatures in YOAD and LOAD that mirror their differential functional responses to tau pathology. In YOAD, reduced precuneus FCD appears to serve as a state marker of cognitive impairment, whereas in LOAD, elevated anterior cingulate FCD suggests compensatory network recruitment consistent with a functional reserve model. These findings underscore FCD's promise as a subtype-specific biomarker for tracking AD progression.