Transcranial alternating current stimulation (tACS)

Abstract

Transcranial alternating current stimulation (tACS) seems likely to open a newera of the field of noninvasive electrical stimulation of the human brain by directlyinterfering with cortical rhythms. It is expected to synchronize (by one single resonancefrequency) or desynchronize (e.g. by the application of several frequencies) corticaloscillations. If applied long enough it may cause neuroplastic effects. In the theta range itmay improve cognition when applied in phase. Alpha rhythms could improve motorperformance, whereas beta intrusion may deteriorate them. TACS with both alpha andbeta frequencies has a high likelihood to induce retinal phosphenes. Gamma intrusioncan possibly interfere with attention. Stimulation in the "ripple" range induces intensitydependent inhibition or excitation in the motor cortex most likely by entrainment ofneuronal networks, whereas stimulation in the low kHz range induces excitation byneuronal membrane interference. TACS in the 200 kHz range may have a potential inoncology. © 2013 Antal and Paulus.