科研之友
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摘要
Background: Periodic stimulation of occipital areas using transcranial alternating current stimulation (tACS) at alpha (alpha) frequency (8-12 Hz) enhances electroencephalographic (EEG) alpha-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 alpha-frequency. @@@ Methods: 12 healthy participants were stimulated at around individual alpha-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 alpha-phase and power changes were compared after and between episodes of alpha-tACS across conditions and against sham. @@@ Results: alpha-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 alpha-aftereffects in response to alpha-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.
- 出版日期2015-5
