Shaping the effects of transcranial direct current stimulation of the human motor cortex
Shaping the effects of transcranial direct current stimulation of the human motor cortex
复制标题
DOI：
10.1152/jn.01312.2006
复制
发表时间：
2007-04-01
影响因子：
2.5
通讯作者：
Paulus, W.
中科院分区：
文献类型：
--
作者：
Nitsche, M. A.;Doemkes, S.;Paulus, W.
经颅直流电刺激 (tDCS) 会引起人脑刺激极性依赖性神经可塑性兴奋性变化。由于其效果持久且使用简单，因此被越来越多地使用。然而，它的一个缺点是焦点低，这是由于 1) 大刺激电极和 2) 功能有效的参考电极（也位于头皮上）造成的。我们的目标是增加 tDCS 的焦点，这可能会改善对刺激功能效应的解释，因为它将其效应限制在更清晰定义的皮质区域。此外，它还可以避免参考电极下 tDCS 产生的不良反向影响，这在需要皮层兴奋性均匀变化的临床环境中特别重要。由于电流密度（电流强度/电极尺寸）决定了 tDCS 的功效，因此增加焦点应通过以下方式实现：1) 减小刺激电极尺寸，但保持电流密度恒定；或2)在恒定电流强度下增加参比电极尺寸。我们针对运动皮层 tDCS 测试了这些假设。结果表明，减小运动皮层直流刺激电极的尺寸可以集中处理 tDCS 引起的兴奋性变化。增加额极参考电极的尺寸会导致对该皮层功能的刺激效率低下，但不会影响 tDCS 产生的运动皮层兴奋性变化。因此，可以通过减小刺激电极的尺寸和增加参考电极的尺寸来集中 tDCS 生成的皮质兴奋性调节。对于 tDCS 的未来应用，此类范式可能有助于实现更具选择性的 tDCS 效果。
Transcranial DC stimulation (tDCS) induces stimulation polarity-dependent neuroplastic excitability shifts in the human brain. Because it accomplishes long-lasting effects and its application is simple, it is used increasingly. However, one drawback is its low focality, caused by 1) the large stimulation electrode and 2) the functionally effective reference electrode, which is also situated on the scalp. We aimed to increase the focality of tDCS, which might improve the interpretation of the functional effects of stimulation because it will restrict its effects to more clearly defined cortical areas. Moreover, it will avoid unwanted reversed effects of tDCS under the reference electrode, which is of special importance in clinical settings, when a homogeneous shift of cortical excitability is needed. Because current density (current strength/electrode size) determines the efficacy of tDCS, increased focality should be accomplished by 1) reducing stimulation electrode size, but keeping current density constant; or 2) increasing reference electrode size under constant current strength. We tested these hypotheses for motor cortex tDCS. The results show that reducing the size of the motor cortex DC-stimulation electrode focalized the respective tDCS-induced excitability changes. Increasing the size of the frontopolar reference electrode rendered stimulation over this cortex functionally inefficient, but did not compromise the tDCS-generated motor cortical excitability shifts. Thus tDCS-generated modulations of cortical excitability can be focused by reducing the size of the stimulation electrode and by increasing the size of the reference electrode. For future applications of tDCS, such paradigms may help to achieve more selective tDCS effects.