Reduced brain functional reserve and altered functional connectivity in patients with multiple sclerosis

Area of Science:

• Neuroscience
• Cognitive Neurology
• Neuroimaging

Background:

• Cognitive dysfunction, particularly affecting attention and working memory, is an early symptom in multiple sclerosis (MS).
• Previous research focused on adaptive functional reorganization via new brain region recruitment to mitigate MS-related cognitive deficits.
• Lesion studies highlight the necessity of specific brain regions for task performance, prompting investigation into altered functional interactions.

Purpose of the Study:

• To investigate whether altered functional interactions between normally recruited brain regions serve as an adaptive mechanism in multiple sclerosis pathology.
• To probe working memory in early multiple sclerosis patients using a modified n-back task and functional connectivity analysis.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to study 21 patients with relapsing-remitting MS and 16 healthy controls.
• A functional connectivity analysis was applied to assess changes in relationships between regional brain activations during a working memory task.
• Task-related brain activations and functional connectivity patterns were compared between MS patients and controls.

Main Results:

• Both groups performed equally on the working memory task, with similar task-related activation regions.
• MS patients exhibited reduced activation in the superior frontal and anterior cingulate gyri compared to controls.
• Functional connectivity analysis revealed altered inter-hemispheric interactions between prefrontal regions in MS patients, suggesting a distinct adaptive mechanism.

Conclusions:

• While cognitive processing involves similar brain regions in MS patients and controls, patients show reduced functional reserve for memory-related cognition.
• Altered inter-hemispheric prefrontal interactions may represent an adaptive strategy to mitigate the clinical expression of cognitive impairments in multiple sclerosis.
• Therapeutic strategies enhancing functional connectivity and promoting adaptive functional changes could help manage cognitive deficits in MS.