Dataset Information

Alpha Power Increase After Transcranial Alternating Current Stimulation at Alpha Frequency (?-tACS) Reflects Plastic Changes Rather Than Entrainment.

ABSTRACT:

Background

Periodic stimulation of occipital areas using transcranial alternating current stimulation (tACS) at alpha (?) frequency (8-12 Hz) enhances electroencephalographic (EEG) ?-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.

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 ?-frequency.

Methods

12 healthy participants were stimulated at around individual ?-frequency for 11-15 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 ?-phase and power changes were compared after and between episodes of ?-tACS across conditions and against sham.

Results

?-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.

Conclusion

Our results indicate that plasticity mechanisms are sufficient to explain ?-aftereffects in response to ?-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.

SUBMITTER: Vossen A

PROVIDER: S-EPMC4464304 | biostudies-literature | 2015 May-Jun

REPOSITORIES: biostudies-literature

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Publications

Alpha Power Increase After Transcranial Alternating Current Stimulation at Alpha Frequency (α-tACS) Reflects Plastic Changes Rather Than Entrainment.

Vossen Alexandra A Gross Joachim J Thut Gregor G

Brain stimulation 20141220 3

<h4>Background</h4>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.<h4>Objective</h4>We tested to what extent plas ...[more]

PMID: 25648377

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