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Updated: Apr 27, 2026
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Simultaneous EEG Monitoring During Transcranial Direct Current Stimulation
Published on: June 17, 2013
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TDCS increases cortical excitability: direct evidence from TMS-EEG
Leonor J Romero Lauro1, Mario Rosanova2, Giulia Mattavelli1
1Department of Psychology, University of Milano-Bicocca, P.za Ateneo Nuovo 1, Milano, Italy.
Summary
Transcranial direct current stimulation (tDCS) increases overall brain excitability during and after stimulation. These effects spread to connected brain regions, not just the targeted area.
Area of Science:
- Neuroscience
- Neuromodulation
- Brain Stimulation
Background:
- The precise mechanisms of transcranial direct current stimulation (tDCS) remain largely unknown.
- tDCS modulates neuronal resting membrane potential, affecting cortical excitability.
- Understanding the spread of tDCS effects to connected regions is unclear.
Purpose of the Study:
- To explore local and global cortical excitability modulation during and after tDCS.
- To investigate the neurophysiological underpinnings of tDCS effects.
- To determine if tDCS affects anatomically connected regions.
Main Methods:
- Combined Transcranial Magnetic Stimulation (TMS) and Electroencephalography (EEG).
- Delivered single-pulse TMS over the left posterior parietal cortex (PPC).
- Recorded EEG during and after 15 minutes of tDCS over the right PPC.
Main Results:
- Global Mean Field Power (GMFP) increased during and after active tDCS (0-100 ms).
- Local Mean Field Power (LMFP) increased in bilateral frontal and parietal clusters post-stimulation.
- No significant changes were observed in temporal clusters.
Conclusions:
- Active tDCS leads to a diffuse increase in cortical excitability.
- tDCS effects extend beyond the directly stimulated area to remote cortical regions.
- Evidence supports the spreading of tDCS effects to contralateral and connected hemispheres.
