Kronberg Greg, Bridi Morgan, Abel Ted, Bikson Marom, Parra Lucas C
Department of Biomedical Engineering, The City College of New York, New York, NY 10031, USA.
Laboratory of Neural Circuits and Behavior, Hussman Institute for Autism, Baltimore, MD 21201, USA.
Brain Stimul. 2017 Jan-Feb;10(1):51-58. doi: 10.1016/j.brs.2016.10.001. Epub 2016 Oct 5.
Transcranial direct current stimulation (tDCS) has been reported to improve various forms of learning in humans. Stimulation is often applied during training, producing lasting enhancements that are specific to the learned task. These learning effects are thought to be mediated by altered synaptic plasticity. However, the effects of DCS during the induction of endogenous synaptic plasticity remain largely unexplored.
OBJECTIVE/HYPOTHESIS: Here we are interested in the effects of DCS applied during synaptic plasticity induction.
To model endogenous plasticity we induced long-term potentiation (LTP) and depression (LTD) at Schaffer collateral synapses in CA1 of rat hippocampal slices. Anodal and cathodal DCS at 20 V/m were applied throughout plasticity induction in both apical and basal dendritic compartments.
When DCS was paired with concurrent plasticity induction, the resulting plasticity was biased towards potentiation, such that LTP was enhanced and LTD was reduced. Remarkably, both anodal and cathodal stimulation can produce this bias, depending on the dendritic location and type of plasticity induction. Cathodal DCS enhanced LTP in apical dendrites while anodal DCS enhanced LTP in basal dendrites. Both anodal and cathodal DCS reduced LTD in apical dendrites. DCS did not affect synapses that were weakly active or when NMDA receptors were blocked.
These results highlight the role of DCS as a modulator, rather than inducer of synaptic plasticity, as well as the dependence of DCS effects on the spatial and temporal properties of endogenous synaptic activity. The relevance of the present results to human tDCS should be validated in future studies.
经颅直流电刺激（tDCS）已被报道可改善人类的多种学习形式。刺激通常在训练期间施加，产生针对所学任务的持久增强效果。这些学习效果被认为是由改变的突触可塑性介导的。然而，直流电刺激（DCS）在内源性突触可塑性诱导过程中的作用在很大程度上仍未得到探索。
目的/假设：在此，我们关注在突触可塑性诱导期间施加DCS的效果。
为模拟内源性可塑性，我们在大鼠海马切片CA1区的Schaffer侧支突触处诱导长时程增强（LTP）和长时程抑制（LTD）。在顶端和基部树突区进行可塑性诱导的整个过程中，施加20 V/m的阳极和阴极DCS。
当DCS与同时进行的可塑性诱导配对时，所产生的可塑性偏向于增强，使得LTP增强而LTD减弱。值得注意的是，阳极和阴极刺激均可产生这种偏向，这取决于树突位置和可塑性诱导的类型。阴极DCS增强顶端树突中的LTP，而阳极DCS增强基部树突中的LTP。阳极和阴极DCS均降低顶端树突中的LTD。DCS不影响弱激活的突触或NMDA受体被阻断时的突触。
这些结果突出了DCS作为突触可塑性调节剂而非诱导剂的作用，以及DCS效应对内源性突触活动的空间和时间特性的依赖性。本研究结果与人类tDCS的相关性应在未来研究中得到验证。
