Whole-Brain Propagation Delays in Multiple Sclerosis, a Combined Tractography-Magnetoencephalography Study

Area of Science:

• Neuroscience
• Biophysics
• Medical Imaging

Background:

• Brain region interactions are influenced by structural connectivity (bundle length, width, myelination, topology).
• Understanding the timing of neural communication is crucial for brain function.
• Existing methods lack in vivo, whole-brain, and single-tract level analysis of functional delays.

Purpose of the Study:

• To introduce and validate an in vivo approach for measuring functional delays across the human brain.
• To integrate magnetoencephalography/electroencephalography (MEG/EEG) data with structural bundle information.
• To create a topochronic map of functional delays and velocities at the single-subject and single-tract level.

Main Methods:

• Developed an in vivo approach combining MEG/EEG with diffusion MRI tractography.
• Measured functional delays and estimated conduction velocities across the whole brain.
• Created a topochronic map correlating structural bundle properties with functional transmission speeds.

Main Results:

• Larger structural brain bundles exhibit faster signal velocities.
• Multiple sclerosis patients show increased network delays compared to controls.
• Structurally lesioned tracts in patients exhibit significantly slower conduction velocities.

Conclusions:

• The novel framework enables patient-specific estimation of functional transmission delays and conduction velocities in the central nervous system (CNS).
• This method is applicable to both healthy and diseased individuals, including those with conditions affecting myelin.
• The findings provide a new tool for assessing brain network integrity and the impact of white matter damage on neural communication.