Modulating transcallosal and intra-hemispheric brain connectivity with tDCS: Implications for interventions in...

Area of Science:

• Neuroscience
• Brain Stimulation
• Neuroimaging

Background:

• Transcranial direct current stimulation (tDCS) alters cortical excitability based on polarity.
• tDCS is explored for modulating inter-hemispheric disinhibition post-stroke, primarily in motor systems.
• The impact of tDCS on language/speech-motor system inter-hemispheric interactions remains unclear.

Purpose of the Study:

• To investigate physiological evidence of inter- and intra-hemispheric connectivity changes.
• To examine tDCS effects on the right inferior frontal gyrus (IFG) using arterial-spin labeling (ASL) MRI.
• To assess if tDCS modulates connectivity in the language/speech-motor network.

Main Methods:

• Nine healthy adults received anodal tDCS to the right IFG using an MR-compatible stimulator.
• Cerebral blood flow was non-invasively imaged using ASL MRI before, during, and after stimulation.
• Regional correlation coefficients in the left/right IFG and right supramarginal gyrus (SMG) were analyzed.

Main Results:

• Inter-hemispheric connectivity (right IFG-left IFG) significantly decreased post-tDCS (p < 0.05).
• Intra-hemispheric connectivity (right IFG-right SMG) significantly increased post-tDCS (p < 0.05).
• Connectivity changes were specific to targeted regions, with no significant alterations in control regions.

Conclusions:

• ASL-MRI can detect tDCS-induced modulation of brain connectivity within and between hemispheres.
• tDCS of the right IFG alters connectivity patterns in a manner consistent with modulating speech-motor networks.
• Findings may inform trial designs aimed at enhancing language/speech-motor functions via non-dominant hemisphere modulation.