Age Differences in Diffusivity in the Locus Coeruleus and its Ascending Noradrenergic Tract

The noradrenergic locus coeruleus (LC) is a small brainstem nucleus that promotes arousal and attention. Recent studies have examined the microstructural properties of the LC using diffusion-weighted magnetic resonance imaging and found unexpected age-related differences in fractional anisotropy - a measure of white matter integrity. Here, we used three datasets (Berlin Aging Study-II, N = 301, the Leipzig Study for Mind-Body-Emotion Interactions, N = 220, and Stockholm Sleepy Brain, N = 49), to replicate published findings and expand them by investigating diffusivity in the LCs ascending noradrenergic bundle. In younger adults, LC fractional anisotropy was significantly lower, compared to older adults. However, in the LCs ascending noradrenergic bundle, we observed significantly higher fractional anisotropy in younger adults, relative to older adults. These findings indicate that diffusivity in the LC versus the ascending noradrenergic bundle are both susceptible to microstructural changes in aging that have opposing effects on fractional anisotropy. HighlightsO_LIFractional anisotropy in the locus coeruleus was lower in younger adults C_LIO_LIFractional anisotropy in the noradrenergic bundle was higher in younger adults C_LIO_LISleep deprivation may affect diffusivity in younger adults more than older adults C_LI