Structure-function coupling using fixel-based analysis and functional magnetic resonance imaging in Alzheimer's...

Area of Science:

• Neuroimaging
• Neuroscience
• Brain Connectivity

Background:

• Functional MRI (fMRI) and diffusion-weighted imaging (DWI) are used to study structural connectivity (SC) and functional connectivity (FC) coupling.
• Disruptions in SC-FC coupling are observed in mild cognitive impairment (MCI) and Alzheimer's disease (AD), correlating with cognitive decline.
• Traditional DWI methods for SC lack fiber-specific information, limiting detailed analysis.

Purpose of the Study:

• To investigate different types of fixel-based SC-FC coupling using advanced DWI analysis.
• To examine the relationship between these coupling measures and cognitive function in an aging cohort.
• To compare coupling patterns across controls, MCI, and AD participants.

Main Methods:

• Utilized data from 392 participants (controls, MCI, AD) from the ADNI study.
• Constructed structural connectomes using fixel metrics: fiber density (FD), fiber-bundle cross-section log (FDC).
• Calculated SC-FC coupling at network, edge, and node levels for each SC metric, analyzing the default mode network (DMN).

Main Results:

• Observed overall DMN, node-, and edge-specific SC-FC coupling differences across SC measures and diagnostic groups.
• Found significant associations between DMN nodal coupling and cognitive measures (Mini-Mental Status Examination, verbal memory).
• Fiber density (FD)-FC and FDC-FC coupling within the DMN were particularly linked to cognitive performance.

Conclusions:

• Different types of fixel-based SC-FC coupling alterations are present across the neurocognitive aging spectrum.
• FD-FC and FDC-FC coupling within the DMN are associated with cognitive functioning.
• Fixel-based analysis provides a more detailed understanding of SC-FC coupling in aging and neurodegenerative conditions.