White Matter Microstructure Predicts Focal and Broad Functional Brain Dedifferentiation in Normal Aging

Area of Science:

• Neuroscience
• Aging Research
• Brain Imaging

Background:

• Ventral visual cortex shows specialized activity for visual processing.
• Aging leads to dedifferentiation, where responses become less selective.
• The inferior longitudinal fasciculus (ILF) is crucial for visual perception.

Purpose of the Study:

• To test if age-related ILF degradation causes ventral visual cortex dedifferentiation.
• To investigate the relationship between ILF white matter integrity and functional selectivity.
• To explore localized and distributed effects of ILF on brain activity.

Main Methods:

• Diffusion-weighted imaging (DWI) to assess white matter diffusivity.
• Functional magnetic resonance imaging (fMRI) to measure functional selectivity.
• Analysis of 281 adults (ages 20-89) from the Dallas Lifespan Brain Study.

Main Results:

• Decreased ILF anisotropy predicted both focal and broad functional dedifferentiation.
• Reduced anisotropy in mid-fusiform ILF predicted less selective face processing.
• Whole ILF integrity predicted broader dedifferentiation between animate and inanimate stimuli.
• The structure-function relationship weakened with age, becoming non-significant after 70.

Conclusions:

• Decreased white matter anisotropy in ILF is linked to maladaptive functional changes in the brain.
• ILF integrity is a key factor in maintaining visual processing selectivity with age.
• These findings are vital for understanding age-related changes in brain function.