Default network activity is a sensitive and specific biomarker of memory in multiple sclerosis

Area of Science:

• Neuroscience
• Medical Imaging
• Cognitive Science

Background:

• Multiple sclerosis (MS) is associated with memory impairment.
• The relationship between MS-related brain atrophy and memory deficits is not fully understood.

Purpose of the Study:

• To investigate default network (DN) deactivation using functional magnetic resonance imaging (fMRI) as a biomarker for memory function in MS patients.
• To assess the neurophysiologic basis of memory impairment in MS.

Main Methods:

• fMRI was used to measure DN deactivation during sustained attention in 28 MS patients.
• High-resolution MRIs quantified brain atrophy.
• Neuropsychological tests assessed episodic memory.
• Hierarchical regression analyzed the predictive power of brain atrophy and DN activity on memory.

Main Results:

• Default network (DN) activity independently predicted memory performance, even after accounting for brain atrophy.
• Greater DN activity (lesser deactivation) correlated with better memory.
• A significant interaction showed that higher DN activity protected against memory impairment in patients with more advanced disease.

Conclusions:

• Maintenance of DN activity during sustained attention is a sensitive and specific neurophysiologic biomarker for episodic memory in MS.
• This biomarker remains significant even when controlling for neuroanatomical changes like brain atrophy.