Associations between MRI-assessed locus coeruleus integrity and cortical gray matter microstructure.

Area of Science:

• Neuroimaging
• Neurodegeneration
• Alzheimer's Disease Research

Background:

• The locus coeruleus (LC) is an early site of tau pathology in Alzheimer's disease (AD).
• Reduced LC integrity, the brain's main norepinephrine source, may impact brain health.
• Macrostructural measures like cortical thickness may not detect early neurodegeneration.

Purpose of the Study:

• To investigate the association between LC structural integrity and cortical gray matter microstructure.
• To determine if LC integrity predicts microstructural changes beyond macrostructural measures in aging men.

Main Methods:

• Used neuromelanin-sensitive MRI to assess LC integrity via contrast-to-noise ratio (LCCNR).
• Employed restriction spectrum imaging (RSI) to model cortical microstructure diffusion compartments (restricted, hindered, free water).
• Analyzed data from 435 men (mean age 67.5).

Main Results:

• Higher LCCNR (greater LC integrity) correlated with increased hindered water diffusion and decreased free water diffusion in cortical regions.
• No significant association was found between LCCNR and cortical thickness after correction.
• Lower LC integrity was linked to microstructural changes suggesting reduced cytoarchitectural barriers.

Conclusions:

• LC integrity, assessed by LCCNR, is associated with cortical microstructure, not cortical thickness.
• These findings support the use of LC imaging and advanced diffusion MRI for assessing brain health.
• LC integrity may serve as an early marker for neurodegenerative processes in the brain.