Resting-State Activity Changes Induced by tDCS in MS Patients and Healthy Controls: A Simultaneous tDCS rs-fMRI Study

Area of Science:

• Neuroscience
• Neuromodulation
• Medical Imaging

Background:

• Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique showing promise for neurodegenerative diseases like multiple sclerosis (MS).
• Understanding the simultaneous and cumulative effects of tDCS on brain activity in MS patients is crucial for optimizing therapeutic strategies.
• Resting-state functional MRI (rs-fMRI) offers insights into regional brain activity through measures like fractional amplitude of low-frequency fluctuations (fALFF).

Purpose of the Study:

• To investigate the immediate (simultaneous) and long-term (cumulative) effects of tDCS on regional brain activity in MS patients.
• To compare tDCS-induced brain activity changes between MS patients and healthy controls (HCs) using concurrent tDCS-MRI.
• To elucidate the neuromodulatory underpinnings and therapeutic potential of tDCS in MS.

Main Methods:

• Recruited 20 MS patients and 28 HCs for tDCS-MRI sessions.
• Measured resting-state functional MRI (rs-fMRI) fALFFs before and during left anodal dorsolateral prefrontal cortex (DLPFC) tDCS (2.0 mA).
• Assessed MS patients again after 20 at-home tDCS sessions to evaluate cumulative effects.

Main Results:

• tDCS induced simultaneous changes in fALFF across cortical and subcortical areas in both groups, with region-specific increases and decreases.
• MS patients showed distinct initial patterns compared to HCs, with reversed patterns observed at follow-up, indicating cumulative effects.
• Greater pre-tDCS fALFFs at follow-up, particularly in the cuneus, suggest long-lasting neuroplastic changes following repeated tDCS treatment (p-FDR < 0.05).

Conclusions:

• tDCS exerts both immediate and cumulative effects on neuronal activity, measurable by rs-fMRI, impacting brain areas beyond the stimulation site.
• These findings highlight tDCS's potential for modulating brain networks in MS, influencing fatigue, and cognitive/motor functions.
• The study underscores the importance of considering both acute and chronic effects of tDCS for therapeutic applications in neurological conditions.