Characterization of Age-related Microstructural Changes in Locus Coeruleus and Substantia Nigra Pars Compacta

TL;DR

This study uses high-resolution diffusion MRI to analyze age-related microstructural changes in the locus coeruleus and substantia nigra, revealing potential early biomarkers for neurodegenerative diseases.

Contribution

It provides novel insights into how microstructural MRI markers in LC and SNpc change with age and relate to cognition, aiding early disease detection.

Findings

LC shows decreased diffusivity and increased fractional anisotropy with age.

LC diffusivity correlates with delayed recall performance.

Iron deposition in SNpc occurs early and progresses with age.

Abstract

Locus coeruleus (LC) and substantia nigra pars compacta (SNpc) degrade with normal aging, but not much is known regarding how these changes manifest in MRI images, or whether these markers predict aspects of cognition. Here, we use high-resolution diffusion-weighted MRI to investigate microstructural and compositional changes in LC and SNpc in young and aged cohorts, as well as their relationship with cognition. In LC, the older cohort exhibited a significant reduction in mean and radial diffusivity, but a significant increase in fractional anisotropy compared to the young cohort. We observed a significant correlation between the decrease in LC mean and radial diffusivities with delayed recall. This observation suggests that LC is involved in retaining cognitive abilities. In addition, we observed that iron deposition in SNpc occurs early in life and continues during normal aging. Since neuronal loss occurs in both LC and SNpc in Parkinson's disease, but occurs only in the LC in Alzheimer's disease, our results may lead to early stage imaging biomarkers for these diseases.