The changes of EEG microstate maps in response to high-definition transcranial direct current stimulation

Transcranial direct current stimulation (tDCS) can modulate the brain's temporal dynamics. While tDCS-induced changes in these dynamics have been reported in clinical populations, how tDCS affects intrinsic brain activity in healthy individuals-particularly as reflected in resting-state electroencephalogram (EEG) microstate sequences-remains unclear. This study aims to examine the effects of high-definition tDCS (HD-tDCS) applied to the right dorsolateral prefrontal cortex (dlPFC) on the modulation of EEG microstates in healthy adults. Utilizing a single-blind, sham-controlled design, we measured the impact of HD-tDCS on four primary microstate metrics: coverage, duration, global explained variance (GEV), and occurrence. Twenty-six healthy young adults participated, undergoing both real and sham stimulation sessions separated by a 3-day washout period. Our findings indicate significant modulation of microstates B and D post-stimulation, with increased occurrence, duration, coverage, and GEV of microstate D and decreased occurrence, coverage, and GEV of microstate B. These findings suggest that targeted stimulation of the right dlPFC can effectively modulate brain microstates linked to attention and visual processing. This study highlights the potential of HD-tDCS to influence the visual and dorsal attention networks, thereby contributing to the enhancement of cognitive functions. Future research should broaden the application of HD-tDCS to investigate its effects across different brain regions and their associated cognitive and emotional processes.