Neuronal microstructural changes in the human brain are associated with neurocognitive aging.

Area of Science:

• Neuroimaging
• Aging Research
• Neuroscience

Background:

• Age-related gray matter (GM) changes are linked to cognitive decline in disorders like Alzheimer's.
• Current MRI studies primarily focus on macroscopic GM changes, missing early, subtle alterations.
• Morphological metrics like cortical thickness are insensitive to pre-atrophy changes.

Purpose of the Study:

• To investigate diffusion MRI as a tool for detecting early microstructural changes in aging brain GM.
• To assess the association between these microstructural changes and cognitive/behavioral deficits.
• To explore if microstructural changes precede macroscopic atrophy and cognitive decline.

Main Methods:

• Utilized the Human Connectome Project-Aging cohort (N=707, ages 36-90).
• Applied the mean apparent diffusion propagator model to quantify microstructural parameters.
• Collected comprehensive cognitive and behavioral test scores.

Main Results:

• Both macro- and microstructural GM features correlated strongly with age.
• Microstructural changes indicated altered cellular morphology, density, extracellular volume, and membrane permeability.
• No correlation was found between macrostructural GM volume and neurobehavioral performance.
• Cortical and subcortical microstructural alterations were significantly associated with neurobehavioral performance.

Conclusions:

• Microstructural alterations in GM precede macroscopic changes and are linked to cognitive decline.
• Increased microstructural heterogeneity and decreased neurite dispersion may serve as early markers of neurocognitive performance.
• Diffusion MRI offers sensitive markers for identifying mechanisms of aging and functional decline.