The relationship between episodic long-term memory and white matter integrity in normal aging

It has been proposed that episodic long-term memory (LTM) declines in normal aging and may be affected by disruption of white matter networks. This was explored in 104 healthy adults aged 50-90 years in the GENIE study; white matter integrity was assessed using diffusion tensor imaging (DTI) in large regions of interest, with additional measures of white matter hyperintensities (WMH), normalized brain and hippocampal volumes. LTM was compared with executive function, working memory and information processing speed. LTM correlated significantly with DTI, WMH and whole brain volume, but not with hippocampal volume. Using linear regression, only DTI measures explained the variance (approximately 19%) in LTM; mediational analyses explored the extent to which other cognitive functions mediate the association between DTI changes and memory. The results suggest that reduced LTM performance in normal aging is related to reduced integrity of a distributed network dependent on white matter pathways supporting episodic memory.