Information processing speed modulation by electrical brain stimulation in multiple sclerosis: towards individually...

Area of Science:

• Neuroscience
• Cognitive Science
• Neurology

Background:

• Information processing speed is crucial for daily life and a primary cognitive deficit in multiple sclerosis (MS).
• Brain imaging suggests the superior parietal lobe's role in information processing speed, offering a target for neuromodulation.
• Transcranial direct current stimulation (tDCS) can modulate brain activity and is being explored for cognitive enhancement.

Purpose of the Study:

• To provide causal evidence for the superior parietal lobe's involvement in information processing speed.
• To investigate the effects of excitatory and inhibitory tDCS on information processing speed in healthy individuals and MS patients.
• To identify predictors of tDCS response in MS patients to tailor future treatments.

Main Methods:

• A registered, randomized, sham-controlled, three-way-blinded, cross-over trial with healthy controls and relapsing-remitting MS patients (N=32/group).
• Participants underwent active or sham tDCS (1.5 mA) while completing the Symbol Digit Modalities Test (SDMT).
• Bayesian generalized linear mixed models were used for data analysis, examining group, stimulation, and polarity interactions.

Main Results:

• Causal evidence confirmed bilateral superior parietal lobe involvement in information processing speed.
• Healthy individuals showed expected responses to anodal (faster) and cathodal (slower) tDCS.
• MS patients exhibited a reversed pattern: less impaired patients benefited from anodal tDCS, while more impaired patients benefited from cathodal tDCS.

Conclusions:

• The superior parietal lobe is causally involved in information processing speed in both health and MS.
• The degree of cognitive impairment in MS patients may reflect compensatory or dysfunctional neuroplasticity.
• Polarity-specific tDCS can counteract these processes, with identified SDMT scores guiding personalized treatment protocols for MS.