Regional age differences in gray matter diffusivity among healthy older adults

Area of Science:

• Neuroimaging
• Gerontology
• Brain Microstructure

Background:

• Aging is linked to brain tissue changes detectable by Diffusion Tensor Imaging (DTI).
• Previous research focused on white matter (WM) age-related diffusion changes, leaving gray matter (GM) diffusion impacts less clear.
• Understanding age-related GM and WM microstructural alterations is crucial for cognitive health in aging.

Purpose of the Study:

• To investigate age-related differences in gray matter (GM) and white matter (WM) microstructure using Diffusion Tensor Imaging (DTI) mean diffusivity (MD) in healthy older adults.
• To explore the relationship between whole-brain GM/WM MD and global cognitive function, assessed via the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).
• To examine decade-specific differences in MD and cognitive performance across age groups (50-59, 60-69, 70+).

Main Methods:

• Diffusion Tensor Imaging (DTI) was used to measure mean diffusivity (MD) in GM and WM across bilateral brain regions (frontal, temporal, parietal, occipital).
• Participants (N=60) were categorized into three age groups: 50-59, 60-69, and 70+.
• Whole-brain GM MD was correlated with cognitive scores from the RBANS.

Main Results:

• Significantly higher MD was found in bilateral temporal and parietal GM, and right hemisphere frontal and temporal WM in older individuals.
• The most pronounced MD differences were observed between the youngest (50-59) and oldest (70+) age groups.
• Elevated whole-brain GM MD correlated with lower RBANS performance in the 60-69 age group.

Conclusions:

• Aging significantly affects GM and WM diffusion differently in healthy older adults.
• These microstructural changes may partially explain cognitive variability observed during older adulthood.
• DTI metrics provide valuable insights into the neurobiological underpinnings of cognitive aging.