Structure-Function Decoupling of the Sensorimotor and Default Mode Networks in Black Americans With MS

Area of Science:

• Neuroscience
• Radiology
• Medical Imaging

Background:

• Multiple sclerosis (MS) disproportionately affects Black individuals, leading to more severe disease progression compared to non-Hispanic White individuals.
• Investigating neural network alterations, specifically in the sensorimotor network (SMN) and default mode network (DMN), is crucial for understanding disability disparities in MS.

Purpose of the Study:

• To compare structural and functional brain connectivity and structure-function decoupling in the SMN and DMN between Black people with MS (B-PwMS) and non-Hispanic White people with MS (NHW-PwMS).
• To explore the relationship between network alterations and clinical outcomes, such as physical and cognitive disability.

Main Methods:

• Utilized 3T-MRI (T1, resting-state functional, diffusion imaging) and clinical assessments (EDSS, SDMT) in 176 participants (B-PwMS, NHW-PwMS, Black healthy controls, NHW-HCs).
• Analyzed structural and functional connectivity using the AAL3 atlas, quantifying global and local network measures.
• Calculated structure-function decoupling by correlating network strengths, controlling for demographics and social determinants of health.

Main Results:

• B-PwMS exhibited higher disability (EDSS) and lower cognitive function (SDMT) than NHW-PwMS, influenced by income and BMI, despite similar disease duration, lesion load, and brain volumes.
• Both B-PwMS and NHW-PwMS showed reduced structural efficiency in SMN and DMN compared to controls.
• B-PwMS displayed significant structural changes in SMN and extensive local rearrangements in SMN/DMN hubs, alongside greater structure-function decoupling in the SMN, trending with increased physical disability.

Conclusions:

• Despite comparable disease burden metrics, B-PwMS exhibit significant alterations in brain network connectivity and greater structure-function decoupling within the SMN and DMN compared to NHW-PwMS.
• The observed structure-function decoupling in the SMN of B-PwMS is associated with increased physical disability, highlighting a potential mechanism for racial disparities in MS progression.