The New Modalities of Transcranial Electric Stimulation: tACS, tRNS, and Other Approaches



The most frequently used low-intensity transcranial electrical stimulation (tES) techniques are transcranial direct current (tDCS), alternating current (tACS), and random noise stimulation (tRNS). During tES, currents are applied with intensities ranging between 0.4 and 2 mA through the human scalp. It has been suggested that tACS interacts with cortical oscillations in a frequency-specific manner at single and using tRNS, at multiple frequencies. All techniques might affect homeostatic mechanisms or the signal-to-noise ratio in the brain. The aim of this review is to summarize basic aspects of tACS and tRNS, their possible neuronal mechanisms and clinical applications.


Transcranial stimulation Alternating current Random noise Brain oscillations 



This work was supported by the DFG (PA 419/15-1) awarded to W.P.


  1. 1.
    Fröhlich F. Experiments and models of cortical oscillations as a target for noninvasive brain stimulation. Prog Brain Res. 2015;222:41–73. doi: 10.1016/bs.pbr.2015.07.025.CrossRefPubMedGoogle Scholar
  2. 2.
    Fröhlich F, Sellers KK, Cordle AL. Targeting the neurophysiology of cognitive systems with transcranial alternating current stimulation. Expert Rev Neurother. 2015;15(2):145–67. doi: 10.1586/14737175.2015.992782.CrossRefPubMedGoogle Scholar
  3. 3.
    Antal A, Boros K, Poreisz C, Chaieb L, Terney D, Paulus W. Comparatively weak after-effects of transcranial alternating current stimulation (tACS) on cortical excitability in humans. Brain Stimul. 2008;1(2):97–105. doi: 10.1016/j.brs.2007.10.001.CrossRefPubMedGoogle Scholar
  4. 4.
    Kar K, Krekelberg B. Transcranial alternating current stimulation attenuates visual motion adaptation. J Neurosci. 2014;34(21):7334–40. doi: 10.1523/JNEUROSCI.5248-13.2014.CrossRefPubMedPubMedCentralGoogle Scholar
  5. 5.
    Mehta AR, Brittain J-S, Brown P. The selective influence of rhythmic cortical versus cerebellar transcranial stimulation on human physiological tremor. J Neurosci. 2014;34(22):7501–8. doi: 10.1523/JNEUROSCI.0510-14.2014.CrossRefPubMedPubMedCentralGoogle Scholar
  6. 6.
    Moliadze V, Atalay D, Antal A, Paulus W. Close to threshold transcranial electrical stimulation preferentially activates inhibitory networks before switching to excitation with higher intensities. Brain Stimul. 2012;5(4):505–11. doi: 10.1016/j.brs.2011.11.004.CrossRefPubMedGoogle Scholar
  7. 7.
    Helfrich RF, Schneider TR, Rach S, Trautmann-Lengsfeld SA, Engel AK, Herrmann CS. Entrainment of brain oscillations by transcranial alternating current stimulation. Curr Biol. 2014;24(3):333–9. doi: 10.1016/j.cub.2013.12.041.CrossRefPubMedGoogle Scholar
  8. 8.
    Jaušovec N, Jaušovec K. Increasing working memory capacity with theta transcranial alternating current stimulation (tACS). Biol Psychol. 2014;96:42–7. doi: 10.1016/j.biopsycho.2013.11.006.CrossRefPubMedGoogle Scholar
  9. 9.
    Reato D, Rahman A, Bikson M, Parra L. Effects of weak transcranial alternating current stimulation on brain activity—a review of known mechanisms from animal studies. Human Neurosci. 2013;7(October):1–8. doi: 10.3389/fnhum.2013.00687.Google Scholar
  10. 10.
    Brittain J-S, Probert-Smith P, Aziz T, Brown P. Tremor suppression by rhythmic transcranial current stimulation. Curr Biol. 2013;23(5):436–40. doi: 10.1016/j.cub.2013.01.068.CrossRefPubMedPubMedCentralGoogle Scholar
  11. 11.
    Chan CY, Hounsgaard J, Nicholson C. Effects of electric fields on transmembrane potential and excitability of turtle cerebellar Purkinje cells in vitro. J Physiol. 1988;402:751–71.CrossRefPubMedPubMedCentralGoogle Scholar
  12. 12.
    Francis JT, Gluckman BJ, Schiff SJ. Sensitivity of neurons to weak electric fields. J Neurosci. 2003;23(19):7255–61.PubMedGoogle Scholar
  13. 13.
    Deans JK, Powell AD, Jefferys JGR. Sensitivity of coherent oscillations in rat hippocampus to AC electric fields. J Physiol. 2007;583(2):555–65. doi: 10.1113/jphysiol.2007.137711.CrossRefPubMedPubMedCentralGoogle Scholar
  14. 14.
    Radman T, Su Y, An JH, Parra LC, Bikson M. Spike timing amplifies the effect of electric fields on neurons: implications for endogenous field effects. J Neurosci. 2007;27(11):3030–6. doi: 10.1523/JNEUROSCI.0095-07.2007.CrossRefPubMedGoogle Scholar
  15. 15.
    Ozen S, Sirota A, Belluscio M, Anastassiou C, Stark E, Koch C. Transcranial electric stimulation entrains cortical neuronal populations in rats. J Neurosci. 2010;30(34):11476–85. doi: 10.1523/JNEUROSCI.5252-09.2010.CrossRefPubMedPubMedCentralGoogle Scholar
  16. 16.
    Reato D, Rahman A, Bikson M, Parra L. Low-intensity electrical stimulation affects network dynamics by modulating population rate and spike timing. J Neurosci. 2010;30(45):15067–79. doi: 10.1523/JNEUROSCI.2059-10.2010.CrossRefPubMedPubMedCentralGoogle Scholar
  17. 17.
    Frohlich F, McCormick D. Endogenous electric fields may guide neocortical network activity. Neuron. 2010;67:129–43. doi: 10.1016/j.neuron.2010.06.005.CrossRefPubMedPubMedCentralGoogle Scholar
  18. 18.
    Holdefer RN, Sadleir R, Russell MJ. Predicted current densities in the brain during transcranial electrical stimulation. Clin Neurophysiol. 2006;117(6):1388–97. doi: 10.1016/j.clinph.2006.02.020.CrossRefPubMedPubMedCentralGoogle Scholar
  19. 19.
    Akhtari M, Bryant HC, Emin D, Merrifield W, Mamelak N, Sutherling WW, et al. A model for frequency dependence of conductivities of the live human skull. Brain Topogr. 2003;16(1):39–55.CrossRefPubMedGoogle Scholar
  20. 20.
    Neuling T, Rach S, Herrmann C. Orchestrating neuronal networks: sustained after-effects of transcranial alternating current stimulation depend upon brain states. Front Hum Neurosci. 2013;7(April):161. doi: 10.3389/fnhum.2013.00161.PubMedPubMedCentralGoogle Scholar
  21. 21.
    Voss U, Holzmann R, Hobson A, Paulus W, Koppehele-Gossel J, Klimke A, et al. Induction of self awareness in dreams through frontal low current stimulation of gamma activity. Nat Neurosci. 2014;17(6):810–2. doi: 10.1038/nn.3719.CrossRefPubMedGoogle Scholar
  22. 22.
    Canolty R, Edwards E, Dalal S, Soltani M, Nagarajan S, Kirsch H, et al. High gamma power is phase-locked to theta oscillations in human neocortex. Sci Rep. 2006;313(September):1626–8. doi: 10.1126/science.1128115.Google Scholar
  23. 23.
    Jensen O, Colgin L. Cross-frequency coupling between neuronal oscillations. Trends Cogn Sci. 2007;11(7):267–9. doi: 10.1016/j.tics.2007.05.003.CrossRefPubMedGoogle Scholar
  24. 24.
    Cabral-Calderin Y, Schmidt-Samoa C, Wilke M. Rhythmic gamma stimulation affects bistable perception. J Cogn Neurosci. 2015;27(7):1298–307. doi: 10.1162/jocn_a_00781.CrossRefPubMedGoogle Scholar
  25. 25.
    Helfrich RF, Knepper H, Nolte G, Strüber D, Rach S, Herrmann CS, et al. Selective modulation of interhemispheric functional connectivity by HD-tACS shapes perception. PLoS Biol. 2014;12(12), e1002031. doi: 10.1371/journal.pbio.1002031.CrossRefPubMedPubMedCentralGoogle Scholar
  26. 26.
    Strüber D, Rach S, Trautmann-Lengsfeld SA, Engel AK, Herrmann CS. Antiphasic 40 Hz oscillatory current stimulation affects bistable motion perception. Brain Topogr. 2014;27(1):158–71. doi: 10.1007/s10548-013-0294-x.CrossRefPubMedGoogle Scholar
  27. 27.
    Neuling T, Rach S, Wagner S, Wolters CH, Herrmann CS. Good vibrations: oscillatory phase shapes perception. Neuroimage. 2012;63(2):771–8. doi: 10.1016/j.neuroimage.2012.07.024.CrossRefPubMedGoogle Scholar
  28. 28.
    Polania R, Nitsche M, Korman C, Batsikadze G, Paulus W. The importance of timing in segregated theta phase-coupling for cognitive performance. Curr Biol. 2012;22(14):1314–8. doi: 10.1016/j.cub.2012.05.021.CrossRefPubMedGoogle Scholar
  29. 29.
    Terney D, Chaieb L, Moliadze V, Antal A, Paulus W. Increasing human brain excitability by transcranial high-frequency random noise stimulation. J Neurosci. 2008;28(52):14147–55. doi: 10.1523/JNEUROSCI.4248-08.2008.CrossRefPubMedGoogle Scholar
  30. 30.
    Schoen I, Fromherz P. Extracellular stimulation of mammalian neurons through repetitive activation of Na + channels by weak capacitive currents on a silicon chip. J Neurophysiol. 2008;100(1):346–57. doi: 10.1152/jn.90287.2008.CrossRefPubMedGoogle Scholar
  31. 31.
    Chaieb L, Antal A, Paulus W. Transcranial random noise stimulation-induced plasticity is NMDA-receptor independent but sodium-channel blocker and benzodiazepines sensitive. Front Neurosci. 2015;9(April):1–9. doi: 10.3389/fnins.2015.00125.Google Scholar
  32. 32.
    Miniussi C, Harris JA, Ruzzoli M. Modelling non-invasive brain stimulation in cognitive neuroscience. Neurosci Biobeh Rev. 2013;37(8):1702–12. doi: 10.1016/j.neubiorev.2013.06.014.CrossRefGoogle Scholar
  33. 33.
    Cappelletti M, Gessaroli E, Hithersay R, Mitolo M, Didino D, Kanai R, et al. Transfer of cognitive training across magnitude dimensions achieved with concurrent brain stimulation of the parietal lobe. J Neurosci. 2013;33(37):14899–907. doi: 10.1523/JNEUROSCI.1692-13.2013.CrossRefPubMedPubMedCentralGoogle Scholar
  34. 34.
    Snowball A, Tachtsidis I, Popescu T, Thompson J, Delazer M, Zamarian L, et al. Long-term enhancement of brain function and cognition using cognitive training and brain stimulation. Curr Biol. 2013;23(11):987–92. doi: 10.1016/j.cub.2013.04.045.CrossRefPubMedPubMedCentralGoogle Scholar
  35. 35.
    Groppa S, Bergmann TO, Siems C, Mölle M, Marshall L, Siebner HR. Slow-oscillatory transcranial direct current stimulation can induce bidirectional shifts in motor cortical excitability in awake humans. Neuroscience. 2010;166(4):1219–25. doi: 10.1016/j.neuroscience.2010.01.019.CrossRefPubMedGoogle Scholar
  36. 36.
    Eggert T, Dorn H, Sauter C, Nitsche M a, Bajbouj M, Danker-Hopfe H. No effects of slow oscillatory transcranial direct current stimulation (tDCS) on sleep-dependent memory consolidation in healthy elderly subjects. Brain Stimul. 2013;6(6):938–45. doi: 10.1016/j.brs.2013.05.006.CrossRefPubMedGoogle Scholar
  37. 37.
    Marshall L, Mölle M, Hallschmid M, Born J. Transcranial direct current stimulation during sleep improves declarative memory. J Neurosci. 2004;24(44):9985–92. doi: 10.1523/JNEUROSCI.2725-04.2004.CrossRefPubMedGoogle Scholar
  38. 38.
    Weisz N, Moratti S, Meinzer M, Dohrmann K, Elbert T. Tinnitus perception and distress is related to abnormal spontaneous brain activity as measured by magnetoencephalography. PLoS Med. 2005;2(6), e153. doi: 10.1371/journal.pmed.0020153.CrossRefPubMedPubMedCentralGoogle Scholar
  39. 39.
    Vanneste S, Fregni F, De Ridder D. Head-to-head comparison of transcranial random noise stimulation, transcranial ac stimulation, and transcranial DC stimulation for tinnitus. Front Psychiatry. 2013;4:31–3. doi: 10.3389/fpsyt.2013.00158.CrossRefGoogle Scholar
  40. 40.
    Joos K, De Ridder D, Vanneste S. The differential effect of low-versus high-frequency random noise stimulation in the treatment of tinnitus. Exp Brain Res. 2015;233(5):1433–40. doi: 10.1007/s00221-015-4217-9.CrossRefPubMedGoogle Scholar
  41. 41.
    Alm P, Dreimanis K. Neuropathic pain: transcranial electric motor cortex stimulation using high frequency random noise. Case report of a novel treatment. J Pain Res. 2013;6:479. doi: 10.2147/JPR.S44648.CrossRefPubMedPubMedCentralGoogle Scholar
  42. 42.
    Krause V, Wach C, Südmeyer M, Ferrea S, Schnitzler A, Pollok B. Cortico-muscular coupling and motor performance are modulated by 20 Hz transcranial alternating current stimulation (tACS) in Parkinson’s disease. Front Hum Neurosci. 2013;7:928. doi: 10.3389/fnhum.2013.00928.CrossRefPubMedGoogle Scholar
  43. 43.
    Fedorov A, Jobke S, Bersnev V, Chibisova A, Chibisova Y, Gall C, et al. Restoration of vision after optic nerve lesions with noninvasive transorbital alternating current stimulation: a clinical observational study. Brain Stimul. 2011;4(4):189–201. doi: 10.1016/j.brs.2011.07.007.CrossRefPubMedGoogle Scholar
  44. 44.
    Gall C, Fedorov AB, Ernst L, Borrmann A, Sabel B a. Repetitive transorbital alternating current stimulation in optic neuropathy. NeuroRehabilitation. 2010;27:335–41. doi: 10.3233/NRE-2010-0617.PubMedGoogle Scholar
  45. 45.
    Herrmann CS, Demiralp T. Human EEG gamma oscillations in neuropsychiatric disorders. Clin Neurophysiol. 2005;116(12):2719–33. doi: 10.1016/j.clinph.2005.07.007.CrossRefPubMedGoogle Scholar
  46. 46.
    Meiron O, Lavidor M. Prefrontal oscillatory stimulation modulates access to cognitive control references in retrospective metacognitive commentary. Clin Neurophysiol. 2014;125(1):77–82. doi: 10.1016/j.clinph.2013.06.013.CrossRefPubMedGoogle Scholar
  47. 47.
    Vossen A, Gross J, Thut G. Alpha power increase after transcranial alternating current stimulation at alpha frequency (α-tACS) reflects plastic changes rather than entrainment. Brain Stimul. 2015;8(3):499–508. doi: 10.1016/j.brs.2014.12.004.CrossRefPubMedPubMedCentralGoogle Scholar
  48. 48.
    Ambrus GG, Antal A, Paulus W. Comparing cutaneous perception induced by electrical stimulation using rectangular and round shaped electrodes. Clin Neurophysiol. 2011;122(4):803–7. doi: 10.1016/j.clinph.2010.08.023.CrossRefPubMedGoogle Scholar
  49. 49.
    Paulus W. Transcranial electrical stimulation (tES – tDCS; tRNS, tACS) methods. Neuropsychol Rehabil. 2011;21(5):602–17. doi: 10.1080/09602011.2011.557292.CrossRefPubMedGoogle Scholar

Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.Department of Clinical NeurophysiologyUniversity Medical Center GöttingenGöttingenGermany

Personalised recommendations