Transcranial direct-current stimulation modulates offline visual oscillatory activity: A magnetoencephalography...

Area of Science:

• Neuroscience
• Electrophysiology
• Brain Stimulation

Background:

• Noninvasive neuromodulation using transcranial direct-current stimulation (tDCS) is widely studied for behavioral and cognitive effects.
• Underlying neuronal mechanisms of tDCS remain poorly understood, with inconsistent findings from neuroimaging and electrophysiology.

Purpose of the Study:

• To investigate tDCS-induced changes in the oscillatory dynamics of visual processing.
• To quantify alterations in brain activity using magnetoencephalography (MEG).

Main Methods:

• Active or sham tDCS was applied using an occipital-frontal electrode configuration.
• Magnetoencephalography (MEG) was recorded during a visual entrainment task.
• Time-frequency analysis with beamforming identified oscillatory responses and assessed power changes.

Main Results:

• Anodal tDCS increased basal alpha levels in the occipital cortex.
• Reduced occipital synchronization at the second harmonic of the stimulus-flicker frequency was observed.
• Active tDCS led to reduced power in regions near the cathode, such as the right inferior frontal gyrus (IFG).

Conclusions:

• Anodal tDCS differentially modulates spontaneous and induced activity in the occipital cortex.
• tDCS may interfere with neuronal population entrainment by visual stimuli.
• Electrode configuration significantly impacts whole-brain dynamics, highlighting the complexity of tDCS neurophysiology.