Executive Functions and Episodic Memory are Associated with Extracellular White Matter Microstructure in Early Old Age

Cortical surface area, cortical thickness, and hippocampal volume are well‐studied in relation to later life cognitive impairments and AD. Fewer studies have investigated how white mater microstructure relates to cognition in late life. Existing work has focused on fractional anisotropy (FA) and mean diffusivity (MD) measures that are thought to capture demyelination and axonal degradation and relate to cognitive decline in normal aging and AD. However, these measures are susceptible to partial volume effects. Here, we evaluated whether executive function and memory are associated with FA and MD after deploying a free‐water (FW) elimination post‐processing method that separates fluid (FW) from tissue (FW‐corrected FA and MD).