IRCCS San Camillo Hospital, Venice, Italy.
IRCCS San Camillo Hospital, Venice, Italy; Department of Movement Sciences, Research Center for Motor Control and Neuroplasticity, KU Leuven, Belgium.
Clin Neurophysiol. 2022 Oct;142:133-142. doi: 10.1016/j.clinph.2022.07.508. Epub 2022 Aug 17.
Transcranial direct current stimulation (tDCS) is a non-invasive technique widely used to investigate brain excitability and activity. However, the variability in both brain and behavioral responses to tDCS limits its application for clinical purposes. This study aims to shed light on state-dependency, a phenomenon that contributes to the variability of tDCS.
To this aim, we investigated changes in spectral activity and functional connectivity in somatomotor regions after Real and Sham tDCS using generalized additive mixed models (GAMMs), which allowed us to investigate how modulation depends on the initial state of the brain.
Results showed that changes in spectral activity, but not connectivity, in the somatomotor regions depend on the initial state of the brain, confirming state-dependent effects. Specifically, we found a non-linear interaction between stimulation conditions (Real vs Sham) and initial state: a reduction of alpha and beta power was observed only in participants that had higher alpha and beta power before Real tDCS.
This study highlights the importance of considering state-dependency to tDCS and shows how it can be taken into account with appropriate statistical models.
Our findings bear insight into tDCS mechanisms, potentially leading to discriminate between tDCS responders and non-responders.
经颅直流电刺激（tDCS）是一种广泛用于研究大脑兴奋性和活动的非侵入性技术。然而，大脑和行为对 tDCS 的反应的可变性限制了其在临床中的应用。本研究旨在阐明状态依存性，这是导致 tDCS 可变性的现象之一。
为此，我们使用广义加性混合模型（GAMM）研究了真实和假 tDCS 后躯体运动区域的光谱活动和功能连接的变化，这使我们能够研究调制如何取决于大脑的初始状态。
结果表明，躯体运动区域的光谱活动变化（但不是连通性）取决于大脑的初始状态，证实了状态依存性效应。具体来说，我们发现刺激条件（真实与假）和初始状态之间存在非线性相互作用：仅在真实 tDCS 前具有较高的 alpha 和 beta 功率的参与者中，才观察到 alpha 和 beta 功率的降低。
本研究强调了考虑 tDCS 状态依存性的重要性，并展示了如何通过适当的统计模型来考虑它。
我们的发现深入了解了 tDCS 的机制，可能导致区分 tDCS 的应答者和非应答者。
