Mapping the aging brain: Insights into microstructural changes from free water-corrected fractional anisotropy

Area of Science:

• Neuroimaging
• Brain Aging
• Diffusion Tensor Imaging

Background:

• Aging significantly impacts brain structure, with diffusion tensor imaging (DTI) revealing changes in fractional anisotropy (FA).
• Previous DTI studies often focus on white matter and cognitive regions, neglecting gray matter and motor areas.
• Traditional DTI metrics can be influenced by partial volume effects, limiting whole-brain microstructural analysis.

Purpose of the Study:

• To investigate aging-related microstructural changes across the entire brain using free water-corrected fractional anisotropy (FAt).
• To compare FAt differences between young adults (YA) and older adults (OA) in both gray and white matter.
• To explore the relationship between age and microstructural changes within the older adult group.

Main Methods:

• Utilized free water-corrected fractional anisotropy (FAt) analysis.
• Conducted a voxel-wise analysis comparing FAt values between 20 young adults and 24 older adults.
• Performed correlation analyses within the older adult group to assess age-related progression.

Main Results:

• Younger adults exhibited higher FAt predominantly in white matter tracts related to motor and non-motor functions.
• Older adults showed higher FAt primarily in gray matter regions, including motor areas and occipital/temporal cortices.
• Correlation analyses confirmed that many observed FAt changes worsen with increasing age in older adults.

Conclusions:

• Distinct patterns of FAt changes in gray versus white matter suggest different aging mechanisms.
• Decreased white matter FAt may indicate axonal degeneration, while increased gray matter FAt could reflect compensatory or pathological processes.
• Future studies incorporating behavioral data are essential to understand the functional implications of gray matter microstructural changes.