A Discussion of tACS Literature
Phase and frequency-dependent effects of transcranial alternating current stimulation on motor cortical excitability.
Nakazono, Hisato, Katsuya Ogata, Tsuyoshi Kuroda, & Shozo Tobimatsu. 2016. Phase and frequency-dependent effects of transcranial alternating current stimulation on motor cortical excitability. PLoS ONE. 11(9): e0162521.
Summary: Nakazona and colleagues (2016) sought to evaluate the phase dependency of oscillatory brain stimulation effects in the human brain. In a series of experiments, the researchers measured TMS-evoked MEPs at multiple phases of 10 and 20 Hz TACS, then used the preferred phase identified to test the same effects at multiple frequencies (5, 10, 20, & 40 Hz). At 90 degrees tACS phase, 10 Hz and 20 Hz tACS demonstrated differentiated effects on MEP amplitudes whereby 10 Hz tACS attenuated MEPs and 20 Hz tACS facilitated MEPs. In a follow-up experiment, TMS delivered at the 90 degree phase of ongoing 5, 10, 20, and 40 Hz tACS demonstrated the frequency specificity of these effects by replicating the 10/20 Hz effects while showing no modulation by 5 or 40 Hz stimulation. The facilitation by 20 Hz was found to remain significant even compared to sham, but not the 10 Hz attenuation.
Contributed by: Christopher Walker, PhD
Every week, there are new and exciting scientific papers published on studies that investigated tACS. Reading and understanding these papers unfortunately requires both access to (sometimes quite expensive) scientific journals and in-depth "insider knowledge." Our goal is to share with you brief summaries of tACS studies that give you a big-picture idea of what the publications are about. There are too many studies to feature all of them but we will continuously update this page. If you have a specific study you would like to get featured, please contact us. The contributors are personnel from the Frohlich Lab and the Carolina Center for Neurostimulation.