Geffen Asher, Bland Nicholas, Sale Martin V
School of Health and Rehabilitation Sciences, The University of Queensland, St Lucia, Queensland, Australia.
Eur J Neurosci. 2025 Mar;61(5):e70042. doi: 10.1111/ejn.70042.
Transcranial alternating current stimulation (tACS) has been proposed to modulate neural activity through two primary mechanisms: entrainment and neuroplasticity. The current study aimed to probe both of these mechanisms in the context of the sensorimotor μ-rhythm using transcranial magnetic stimulation (TMS) and electroencephalography (EEG) to assess entrainment of corticospinal excitability (CSE) during stimulation (i.e., online) and immediately following stimulation, as well as neuroplastic aftereffects on CSE and μ EEG power. Thirteen participants received three sessions of stimulation. Each session consisted of 90 trials of μ-tACS tailored to each participant's individual μ frequency (IMF), with each trial consisting of 16 s of tACS followed by 8 s of rest (for a total of 24 min of tACS and 12 min of rest per session). Motor-evoked potentials (MEPs) were acquired at the start and end of the session (n = 41), and additional MEPs were acquired across the different phases of tACS at three epochs within each tACS trial (n = 90 for each epoch): early online, late online and offline echo. Resting EEG activity was recorded at the start, end and throughout the tACS session. The data were then pooled across the three sessions for each participant to maximise the MEP sample size per participant. We present preliminary evidence of CSE entrainment persisting immediately beyond tACS and have also replicated the plastic CSE facilitation observed in previous μ-tACS studies, thus supporting both entrainment and neuroplasticity as mechanisms by which tACS can modulate neural activity.
经颅交流电刺激（tACS）已被提出可通过两种主要机制调节神经活动：诱捕和神经可塑性。本研究旨在利用经颅磁刺激（TMS）和脑电图（EEG）在感觉运动μ节律的背景下探究这两种机制，以评估刺激期间（即在线）及刺激后立即出现的皮质脊髓兴奋性（CSE）的诱捕情况，以及对CSE和μ脑电图功率的神经可塑性后效应。13名参与者接受了三次刺激。每次刺激由90次针对每个参与者个体μ频率（IMF）定制的μ-tACS试验组成，每次试验包括16秒的tACS，随后是8秒的休息（每次刺激共24分钟的tACS和12分钟的休息）。在每次刺激的开始和结束时采集运动诱发电位（MEP）（n = 41），并在每次tACS试验中的三个时间点（每个时间点n = 90），即早期在线、晚期在线和离线回声期，在tACS的不同阶段采集额外的MEP。在tACS开始、结束时以及整个过程中记录静息EEG活动。然后将每个参与者三次刺激的数据汇总，以最大化每个参与者的MEP样本量。我们提供了初步证据，证明CSE诱捕在tACS结束后仍立即持续存在，并且还重复了先前μ-tACS研究中观察到的可塑性CSE促进作用，从而支持诱捕和神经可塑性作为tACS调节神经活动的机制。
