Is impaired information processing speed a matter of structural or functional damage in MS?

Area of Science:

• Neuroscience
• Neurology
• Medical Imaging

Background:

• Cognitive deficits, particularly in information processing speed (IPS), are prevalent in multiple sclerosis (MS).
• The neurobiological underpinnings of these IPS deficits in MS remain incompletely understood.
• Understanding these mechanisms is crucial for developing targeted interventions.

Purpose of the Study:

• To investigate the relationship between structural and functional brain changes and IPS performance in MS patients.
• To differentiate the impact of structural versus functional alterations on IPS.
• To explore the combined effect of structural and functional damage on IPS.

Main Methods:

• Information processing speed (IPS) was assessed using the Symbol Digit Modalities Test (SDMT) in 330 MS patients and 96 controls.
• Structural brain integrity was evaluated using volumetric measures and diffusion tensor imaging (DTI).
• Functional connectivity changes were assessed using resting-state functional magnetic resonance imaging (fMRI).

Main Results:

• Patients with IPS impairment exhibited reduced deep gray matter volume and white matter integrity, alongside increased functional connectivity, compared to those with preserved IPS.
• Predominantly structural damage was associated with worse IPS performance (z = -1.49) than predominantly functional changes (z = -0.84).
• Severe combined structural and functional damage correlated with the most significant IPS deficits (z = -1.95).

Conclusions:

• Structural brain damage is a stronger predictor of IPS performance in MS than functional changes alone.
• Integrating both structural and functional data reveals a more nuanced, stepwise decline in IPS.
• Within similar levels of structural damage, greater functional alterations exacerbate IPS deficits in MS patients.