Task-concurrent anodal tDCS modulates bilateral plasticity in the human suprahyoid motor cortex

Area of Science:

• Neuroscience
• Motor Control
• Rehabilitation

Background:

• Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique.
• Modulating cortical excitability is crucial for understanding and treating motor control disorders.
• Suprahyoid muscles play a vital role in swallowing function.

Purpose of the Study:

• To investigate the effects of anodal tDCS on suprahyoid motor evoked potentials (MEPs).
• To compare the impact of tDCS applied over hemispheres with stronger versus weaker suprahyoid projections.
• To assess the duration of tDCS effects on MEPs in both stimulated and non-stimulated hemispheres during a swallowing task.

Main Methods:

• Thirty healthy volunteers participated in two experimental sessions with a crossover design.
• Anodal tDCS or sham stimulation was applied over hemispheres with stronger or weaker suprahyoid projections.
• Suprahyoid MEPs were recorded before and at multiple time points after stimulation.

Main Results:

• Anodal tDCS produced long-lasting increases in suprahyoid MEPs on the stimulated side in both groups.
• Stimulation over stronger projection areas did not affect MEPs in the non-stimulated hemisphere.
• Stimulation over weaker projection areas significantly increased MEPs in the non-stimulated hemisphere 30-90 minutes post-stimulation.

Conclusions:

• Anodal tDCS exhibits differential effects on suprahyoid MEPs based on stimulation site and hemisphere.
• These findings highlight the potential of targeted anodal tDCS for treating swallowing disorders like dysphagia, particularly post-stroke.