Fiber Ball White Matter Modeling Reveals Microstructural Alterations in Healthy Brain Aging.

Area of Science:

• Neuroimaging
• White Matter Microstructure
• Aging

Background:

• Age-related white matter degeneration involves myelin and axon loss, particularly in late-myelinating regions.
• Conventional diffusion MRI (dMRI) shows increased diffusivity with age but lacks tissue-specific detail.
• Fiber Ball White Matter (FBWM) modeling estimates intra-axonal and extra-axonal properties for enhanced biological interpretation.

Purpose of the Study:

• To investigate the microstructural mechanisms of white matter changes in healthy aging using FBWM.
• To compare age-related microstructural alterations in late- vs. early-myelinating white matter regions.
• To assess FBWM's potential for detecting early pathological changes.

Main Methods:

• Utilized FBWM modeling on dMRI data from 63 healthy adults (ages 45-85).
• Computed conventional dMRI and FBWM metrics in early- (splenium, projection tracts) and late-myelinating (genu, association tracts) regions.
• Examined age associations with metrics, comparing late- vs. early-myelinating regions.

Main Results:

• Conventional dMRI confirmed age-related diffusivity increases in late-myelinating regions.
• FBWM revealed age-related intra- and extra-axonal changes, indicating myelin breakdown and smaller axon loss.
• These microstructural changes were more pronounced in late-myelinating regions.

Conclusions:

• FBWM modeling provides novel, microstructure-specific insights into healthy white matter aging.
• FBWM findings corroborate histopathological studies of aged brains.
• Advanced modeling techniques like FBWM show promise for early detection of neurodegenerative changes.