FENNSI Group, Hospital Nacional de Parapléjicos, SESCAM, Toledo, Spain.
Servicio de Neurología, Hospital La Mancha Centro, SESCAM, Alcázar de San Juan, Spain.
Brain Stimul. 2012 Jul;5(3):214-222. doi: 10.1016/j.brs.2011.05.001. Epub 2011 Jun 1.
Transcranial direct current stimulation (tDCS) is a noninvasive technique that has been investigated as a therapeutic tool for different neurologic disorders. Neuronal excitability can be modified by application of DC in a polarity-specific manner: anodal tDCS increases excitability, while cathodal tDCS decreases excitability. Previous research has shown that simultaneous bilateral tDCS of the human motor cortex facilitates motor performance in the anodal stimulated hemisphere much more than when the same hemisphere is stimulated using unilateral anodal motor cortex tDCS.
The main purpose of this study was to determine whether simultaneous bilateral tDCS is able to increase cortical excitability in one hemisphere whereas decreasing cortical excitability in the contralateral hemisphere. To test our hypothesis, cortical excitability before and after bilateral motor cortex tDCS was evaluated. Moreover, the effects of bilateral tDCS were compared with those of unilateral motor cortex tDCS.
We evaluated cortical excitability in healthy volunteers before and after unilateral or bilateral tDCS using transcranial magnetic stimulation.
We demonstrated that simultaneous application of anodal tDCS over the motor cortex and cathodal tDCS over the contralateral motor cortex induces an increase in cortical excitability on the anodal-stimulated side and a decrease in the cathodal stimulated side. We also used the electrode montage (motor cortex-contralateral orbit) method to compare the bilateral tDCS montage with unilateral tDCS montage. The simultaneous bilateral tDCS induced similar effects to the unilateral montage on the cathode-stimulated side. On the anodal tDCS side, the simultaneous bilateral tDCS seems to be a slightly less robust electrode arrangement compared with the placement of electrodes in the motor cortex-contralateral orbit montage. We also found that intersubject variability of the excitability changes that were induced by the anodal motor cortex tDCS using the bilateral montage was lower than that with the unilateral montage.
This is the first study in which cortical excitability before and after bilateral motor cortex tDCS was extensively evaluated, and the effects of bilateral tDCS were compared with unilateral motor cortex tDCS. Simultaneous bilateral tDCS seems to be a useful tool to obtain increases in cortical excitability of one hemisphere whereas causing decreases of cortical excitability in the contralateral hemisphere (e.g.,to treat stroke).
经颅直流电刺激（tDCS）是一种非侵入性技术，已被研究作为治疗不同神经疾病的工具。直流电以极性特异性的方式调节神经元兴奋性：阳极 tDCS 增加兴奋性，而阴极 tDCS 降低兴奋性。先前的研究表明，双侧人类运动皮层的同时 tDCS 比同侧使用单侧阳极运动皮层 tDCS 刺激更能促进阳极刺激半球的运动表现。
本研究的主要目的是确定双侧 tDCS 是否能够增加一个半球的皮质兴奋性，同时降低对侧半球的皮质兴奋性。为了验证我们的假设，我们在双侧运动皮层 tDCS 前后评估了皮质兴奋性。此外，我们比较了双侧 tDCS 的效果与单侧运动皮层 tDCS 的效果。
我们使用经颅磁刺激在健康志愿者中评估单侧或双侧 tDCS 前后的皮质兴奋性。
我们证明，在运动皮层上施加阳极 tDCS，在对侧运动皮层上施加阴极 tDCS 的同时应用会导致阳极刺激侧的皮质兴奋性增加，阴极刺激侧的皮质兴奋性降低。我们还使用电极排列（运动皮层-对侧眼眶）方法将双侧 tDCS 排列与单侧 tDCS 排列进行比较。双侧 tDCS 诱导的阴极刺激侧的效果与单侧排列相似。在阳极 tDCS 侧，与将电极放置在运动皮层-对侧眼眶排列相比，双侧 tDCS 的排列似乎是一种稍不稳健的电极排列。我们还发现，使用双侧排列诱导的阳极运动皮层 tDCS 引起的兴奋性变化的个体间可变性低于单侧排列。
这是首次广泛评估双侧运动皮层 tDCS 前后皮质兴奋性的研究，并且比较了双侧 tDCS 的效果与单侧运动皮层 tDCS 的效果。双侧 tDCS 似乎是一种有用的工具，可以增加一个半球的皮质兴奋性，同时降低对侧半球的皮质兴奋性（例如，治疗中风）。
