Reorganization of brain structural networks in aging: A longitudinal study

Area of Science:

• Neuroscience
• Gerontology
• Network Science

Background:

• Normal aging involves brain changes leading to cognitive decline.
• Structural connectivity (SC) disruption may contribute to age-related cognitive deterioration.
• Previous studies often focused on average whole-brain or specific network connectivity during aging.

Purpose of the Study:

• To characterize longitudinal changes in white matter (WM) structural brain networks over time.
• To identify sub-networks with altered connectivity during aging.
• To associate longitudinal SC changes with cognitive function and network topology.

Main Methods:

• Diffusion magnetic resonance imaging (dMRI) to derive WM structural networks.
• Neurocognitive testing to assess cognitive status.
• Analysis of longitudinal changes in connectivity weight and network topology in older adults over approximately 5 years.

Main Results:

• Observed age-related changes in SC, including decreased intra-hemispheric (association fibers) and increased inter-hemispheric (association, commissural, projection fibers) connectivity.
• Identified a loss of two network hubs and decreased connector-hub connectivity, indicating reduced integration.
• Noted an increase in provincial hubs, suggesting enhanced segregation within the brain network.

Conclusions:

• Aging triggers a significant reorganization of the brain's structural network.
• These SC changes, characterized by altered integration and segregation, are linked to cognitive aging.
• Findings support the 'last-in-first-out' hypothesis regarding fiber tract involvement in aging-related network changes.