Apparent Diffusion Coefficient fMRI shines light on white matter resting-state connectivity compared to BOLD

Area of Science:

• Neuroimaging
• Functional Magnetic Resonance Imaging (fMRI)
• White Matter (WM) and Gray Matter (GM) Connectivity

Background:

• Resting-state functional magnetic resonance imaging (fMRI) typically uses blood oxygen level-dependent (BOLD) contrast to measure functional connectivity (FC).
• BOLD contrast's reliance on neurovascular coupling can limit sensitivity, particularly in white matter (WM), where signals are often considered noise.
• Recent findings suggest WM BOLD signals, though smaller, reflect brain activity similarly to gray matter (GM).

Purpose of the Study:

• To introduce and evaluate apparent diffusion coefficient fMRI (ADC-fMRI) as a novel functional contrast for brain connectivity.
• To compare the efficacy of ADC-fMRI and BOLD-fMRI in measuring functional connectivity in both gray matter (GM) and white matter (WM).
• To assess ADC-fMRI's ability to capture neuromorphological fluctuations related to brain activity.

Main Methods:

• Comparison of functional connectivity (FC) derived from BOLD-fMRI and ADC-fMRI in both gray matter (GM) and white matter (WM).
• Analysis of key network metrics including average clustering and average node strength.
• Evaluation of inter-subject similarity in connectivity patterns between the two fMRI techniques.

Main Results:

• ADC-fMRI successfully mirrors BOLD-fMRI functional connectivity (FC) in gray matter (GM).
• ADC-fMRI reveals more robust FC in white matter (WM) compared to BOLD-fMRI.
• ADC-fMRI demonstrates higher average clustering, average node strength, and inter-subject similarity in WM networks.

Conclusions:

• ADC-fMRI is a promising functional contrast agent for brain imaging.
• ADC-fMRI offers enhanced sensitivity for detecting functional connectivity (FC) in white matter (WM).
• ADC-fMRI provides a reliable method for studying brain networks incorporating both gray and white matter.