The basics of tACS:
tACS is similar to tDCS as a neuromodulatory technique, but instead of applying a direct electrical current, tACS oscillates a sinusoidal current at a chosen frequency to interact with the brain’s natural cortical oscillations. Generally, a large electrode is placed over an area of interest which applies stimulation while a reference electrode is placed in a neutral location. When a single, consonant frequency is applied the exogenous oscillation can synchronize with the brain’s endogenous frequency. When several oscillations are pulsated, desynchronization of cortical oscillations can occur. As such, tACS effects are contingent on the frequency, amplitude, and phase applied. tACS applied in the EEG frequency range (0.1-80Hz) can entrain neural oscillations, augmenting them. In higher ranges (1-5 kHz), oscillation interaction is unlikely to occur, but cortical excitability has been suggested.1The exact mechanisms of action are still unclear, but the effects are related to the manipulation of brain oscillations and thus information transfer, and the corresponding biochemical alterations which may result. Some areas tACS is currently being explored include: Parkinson’s, Schizophrenia, tumor retardation, cognitive enhancement, Tinnitus, and motor performance.
Where can I get tACS?
tACS belongs to the same category as tDCS by FDA regulations; an explicit opinion has not been made. Therefore any company selling a device cannot indicate a clinical application for its use.
1Antal, A., Boros, K., Poreisz, C., Chaieb, L., Terney, D., & Paulus, W. (2008). Comparatively weak after-effects of transcranial alternating current stimulation (tACS) on cortical excitability in humans. Brain stimulation, 1(2), 97-105.