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Updated: Feb 11, 2026

Functional Mapping with Simultaneous MEG and EEG
Published on: June 14, 2010
tACS-mediated modulation of the auditory steady-state response as seen with MEG
Petteri Hyvärinen1, Dawoon Choi2, Gianpaolo Demarchi3
1Department of Otorhinolaryngology-Head and Neck Surgery, University of Helsinki and Helsinki University Hospital, Biomedicum Helsinki 1, P.O. Box 220, FI-00029 HUS, Finland; Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Finland.
Background:
Previous studies have shown that transcranial electrical stimulation can be successfully applied during simultaneous MEG measurements. In particular, using beamforming they have established that changes of stimulus induced as well as evoked activity can be inspected during transcranial alternating current stimulation (tACS).
Objective/Hypothesis:
We studied tACS-mediated changes of the auditory steady-state response (ASSR), hypothesizing that-due to the putatively inhibitory role of alpha oscillations-these evoked responses would be diminished.
Methods:
We compared ASSRs in conditions with and without 12-Hz and 6.5-Hz sinusoidal 1.5 mA tACS, applied bilaterally over temporal areas. Source-level activity was estimated using a linearly constrained minimum variance beamformer and compared across tACS conditions using paired t-tests following a condition-internal normalization procedure.
Conclusions:
By separating the electrical and auditory stimulation to non-overlapping parts of the frequency spectrum, we were able to compare auditory-evoked steady-state activity across tACS conditions. We observed a significant decrease in normalized ASSR power in the 12-Hz tACS condition, illustrating that tACS could induce immediate changes in auditory evoked activity. This study sets a methodology to further interrogate the causal roles of oscillatory dynamics in auditory cortices, as well as suggests perspectives for employing tACS in clinical contexts.
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