Alpha power increase after transcranial alternating current stimulation at alpha frequency (α-tacs) reflects plastic changes rather than entrainment

Vossen, A., Gross, J. and Thut, G. (2015) Alpha power increase after transcranial alternating current stimulation at alpha frequency (α-tacs) reflects plastic changes rather than entrainment. Brain Stimulation, 8(3), pp. 499-508. (doi:10.1016/j.brs.2014.12.004) (PMID:25648377) (PMCID:PMC4464304)

[img]
Preview
Text
101443.pdf - Published Version
Available under License Creative Commons Attribution.

1MB

Abstract

Background: Periodic stimulation of occipital areas using transcranial alternating current stimulation (tACS) at alpha (α) frequency (8–12 Hz) enhances electroencephalographic (EEG) α-oscillation long after tACS-offset. Two mechanisms have been suggested to underlie these changes in oscillatory EEG activity: tACS-induced entrainment of brain oscillations and/or tACS-induced changes in oscillatory circuits by spike-timing dependent plasticity.<p></p> Objective: We tested to what extent plasticity can account for tACS-aftereffects when controlling for entrainment “echoes.” To this end, we used a novel, intermittent tACS protocol and investigated the strength of the aftereffect as a function of phase continuity between successive tACS episodes, as well as the match between stimulation frequency and endogenous α-frequency.<p></p> Methods: 12 healthy participants were stimulated at around individual α-frequency for 15–20 min in four sessions using intermittent tACS or sham. Successive tACS events were either phase-continuous or phase-discontinuous, and either 3 or 8 s long. EEG α-phase and power changes were compared after and between episodes of α-tACS across conditions and against sham.<p></p> Results: α-aftereffects were successfully replicated after intermittent stimulation using 8-s but not 3-s trains. These aftereffects did not reveal any of the characteristics of entrainment echoes in that they were independent of tACS phase-continuity and showed neither prolonged phase alignment nor frequency synchronization to the exact stimulation frequency.<p></p> Conclusion: Our results indicate that plasticity mechanisms are sufficient to explain α-aftereffects in response to α-tACS, and inform models of tACS-induced plasticity in oscillatory circuits. Modifying brain oscillations with tACS holds promise for clinical applications in disorders involving abnormal neural synchrony.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Thut, Professor Gregor and Gross, Professor Joachim
Authors: Vossen, A., Gross, J., and Thut, G.
College/School:College of Medical Veterinary and Life Sciences > Institute of Neuroscience and Psychology
Journal Name:Brain Stimulation
Publisher:Elsevier Inc.
ISSN:1935-861X
ISSN (Online):1876-4754
Copyright Holders:Copyright © 2014 Elsevier Inc.
First Published:First published in Brain Stimulation 2014
Publisher Policy:Reproduced under a Creative Commons License

University Staff: Request a correction | Enlighten Editors: Update this record

Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
597911Natural and modulated neural communication: State-dependent decoding and driving of human Brain OscillationsGregor ThutWellcome Trust (WELLCOME)098434/Z/12/ZINP - CENTRE FOR COGNITIVE NEUROIMAGING
597051Natural and modulated neural communication: State-dependent decoding and driving of human Brain Oscillations.Joachim GrossWellcome Trust (WELLCOME)098433/Z/12/ZINP - CENTRE FOR COGNITIVE NEUROIMAGING