Dynamic modulation of intrinsic functional connectivity by transcranial direct current stimulation

Area of Science:

• Neuroscience
• Brain Stimulation
• Cognitive Science

Background:

• Transcranial direct current stimulation (tDCS) modulates cortical excitability, impacting behavior and learning.
• Bilateral tDCS over primary sensorimotor cortices (SM1) shows greater effects on motor performance than unilateral tDCS.
• Understanding the neural mechanisms of bilateral vs. unilateral tDCS is crucial.

Purpose of the Study:

• To investigate changes in resting-state functional connectivity induced by unilateral and bilateral tDCS over SM1.
• To compare the network-level effects of different tDCS configurations.
• To elucidate the neural underpinnings of enhanced motor performance with bilateral tDCS.

Main Methods:

• Randomized, single-blind, crossover design with 12 healthy subjects.
• Functional magnetic resonance imaging (fMRI) at rest before, during, and after 20 minutes of unilateral, bilateral, and sham tDCS over SM1.
• Eigenvector centrality mapping (ECM) to analyze whole-brain functional connectivity changes.

Main Results:

• Both unilateral and bilateral tDCS induced widespread functional connectivity changes compared to sham.
• Bilateral tDCS primarily affected motor and prefrontal regions.
• Unilateral tDCS modulated prefrontal, parietal, and cerebellar areas, with no direct effect under the electrode.
• Connectivity changes exhibited nonlinear and temporally dispersed patterns.

Conclusions:

• tDCS interventions induce network-specific functional connectivity alterations.
• Bilateral tDCS over SM1 engages distinct brain networks compared to unilateral tDCS.
• Findings support a network-based understanding of tDCS effects on brain function and behavior.