Reduced Network Dynamics on Functional MRI Signals Cognitive Impairment in Multiple Sclerosis

Area of Science:

• Neuroscience
• Radiology
• Cognitive Science

Background:

• Previous studies show functional network disturbances and reduced brain efficiency in multiple sclerosis (MS).
• Brain network dynamics correlate strongly with cognitive function.
• Investigating network dynamics in MS is crucial for understanding cognitive impairment.

Purpose of the Study:

• To investigate functional network dynamics using functional MRI (fMRI) in cognitively impaired versus cognitively preserved patients with MS.
• To identify differences in regional functional network dynamics, specifically eigenvector centrality dynamics.

Main Methods:

• Secondary analysis of prospectively acquired fMRI data (3 T) using a sliding-window approach.
• Comparison of regional functional network dynamics between cognitively impaired and preserved MS groups via clusterwise permutation testing.
• Correlation and hierarchical clustering analysis to assess network interplay.

Main Results:

• Cognitively impaired MS patients showed reduced centrality dynamics in default-mode, frontoparietal, and visual networks compared to cognitively preserved individuals.
• A significant loss of negative correlation between default-mode and visual network fluctuations was observed in cognitively impaired MS patients.
• The default-mode and visual networks normally exhibit negatively correlated fluctuations, which was nearly lost in the impaired group.

Conclusions:

• Cognitively impaired MS patients demonstrate reduced network dynamics in key brain regions on fMRI.
• A loss of interplay between the default-mode and visual networks is a characteristic of cognitive impairment in MS.
• These findings provide insights into the neural mechanisms underlying cognitive dysfunction in multiple sclerosis.