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Updated: Feb 15, 2026
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Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation tACS
Published on: January 22, 2016
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Frequency-dependent tACS modulation of BOLD signal during rhythmic visual stimulation
Yuhui Chai1,2,3, Jingwei Sheng1,3, Peter A Bandettini1
1Section on Functional Imaging Methods, Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland.
Human Brain Mapping
|February 2, 2018
Summary
Transcranial alternating current stimulation (tACS) modulates brain activity, as shown by fMRI. This study reveals tACS effects on visual rhythms when frequencies match, mapping brain responses with high spatial resolution.
Area of Science:
- Neuroscience
- Brain Stimulation
- Neuroimaging
Background:
- Transcranial alternating current stimulation (tACS) modulates brain oscillations, but its spatial effects and hemodynamic responses are unclear.
- Previous studies primarily used electroencephalogram (EEG), limiting spatial resolution.
- Functional magnetic resonance imaging (fMRI) offers whole-brain coverage and high spatial resolution for assessing tACS impacts.
Purpose of the Study:
- To investigate the spatial distribution and hemodynamic response of tACS-induced modulation of cortical oscillations.
- To explore the effects of tACS on stimulus-induced brain rhythms using fMRI.
- To bridge tACS research domains and establish fMRI as a tool for localizing tACS effects.
Main Methods:
- fMRI was used to measure blood-oxygen-level-dependent (BOLD) signals during tACS application.
- tACS was applied at various frequencies (4, 8, 16, 32 Hz) during rhythmic visual stimulation (8 and 16 Hz).
- BOLD signal differences were analyzed between tACS-ON and tACS-OFF conditions, and across different frequency pairings.
Main Results:
- Significant tACS modulation of BOLD responses occurred when tACS frequency matched the visual flicker frequency or its second harmonic.
- Modulation effects were primarily observed in task-activated regions and areas targeted by tACS current.
- fMRI successfully localized tACS effects on stimulus-induced brain rhythms.
Conclusions:
- fMRI can effectively localize the effects of tACS on brain activity, particularly on stimulus-induced rhythms.
- tACS modulation is frequency-dependent and spatially constrained to targeted and task-relevant brain regions.
- This research provides a novel approach for understanding cognitive processes influenced by brain oscillations.
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