Department of Biomedical Engineering, The City College of New York, CUNY, 160 Convent Avenue, New York, NY, USA.
Department of Biomedical Engineering, The City College of New York, CUNY, 160 Convent Avenue, New York, NY, USA.
Brain Stimul. 2020 Mar-Apr;13(2):287-301. doi: 10.1016/j.brs.2019.10.014. Epub 2019 Oct 18.
There is evidence that transcranial direct current stimulation (tDCS) can improve learning performance. Arguably, this effect is related to long term potentiation (LTP), but the precise biophysical mechanisms remain unknown.
We propose that direct current stimulation (DCS) causes small changes in postsynaptic membrane potential during ongoing endogenous synaptic activity. The altered voltage dynamics in the postsynaptic neuron then modify synaptic strength via the machinery of endogenous voltage-dependent Hebbian plasticity. This hypothesis predicts that DCS should exhibit Hebbian properties, namely pathway specificity and associativity.
We studied the effects of DCS applied during the induction of LTP in the CA1 region of rat hippocampal slices and using a biophysical computational model.
DCS enhanced LTP, but only at synapses that were undergoing plasticity, confirming that DCS respects Hebbian pathway specificity. When different synaptic pathways cooperated to produce LTP, DCS enhanced this cooperation, boosting Hebbian associativity. Further slice experiments and computer simulations support a model where polarization of postsynaptic pyramidal neurons drives these plasticity effects through endogenous Hebbian mechanisms. The model is able to reconcile several experimental results by capturing the complex interaction between the induced electric field, neuron morphology, and endogenous neural activity.
These results suggest that tDCS can enhance associative learning. We propose that clinical tDCS should be applied during tasks that induce Hebbian plasticity to harness this phenomenon, and that the effects should be task specific through their interaction with endogenous plasticity mechanisms. Models that incorporate brain state and plasticity mechanisms may help to improve prediction of tDCS outcomes.
有证据表明，经颅直流电刺激（tDCS）可以提高学习成绩。可以说，这种效果与长时程增强（LTP）有关，但确切的生物物理机制尚不清楚。
我们提出，在持续的内源性突触活动过程中，直流电刺激（DCS）会导致突触后膜电位发生微小变化。然后，突触后神经元的电压动力学变化通过内源性电压依赖性赫布型可塑性机制来改变突触强度。该假设预测 DCS 应该表现出赫布型特性，即路径特异性和关联性。
我们研究了 DCS 在大鼠海马切片 CA1 区 LTP 诱导过程中应用的效果，并使用了生物物理计算模型。
DCS 增强了 LTP，但仅在正在发生可塑性的突触上增强，这证实了 DCS 尊重赫布型路径特异性。当不同的突触途径协同产生 LTP 时，DCS 增强了这种协同作用，提高了赫布型关联性。进一步的切片实验和计算机模拟支持一种模型，即通过内源性赫布型机制，极化突触后锥体细胞驱动这些可塑性效应。该模型能够通过捕获诱导电场、神经元形态和内源性神经活动之间的复杂相互作用，调和几个实验结果。
这些结果表明 tDCS 可以增强联想学习。我们建议，在诱导赫布型可塑性的任务中应用临床 tDCS 以利用这种现象，并且通过与内源性可塑性机制的相互作用，效果应该是特定于任务的。纳入大脑状态和可塑性机制的模型可能有助于提高 tDCS 结果的预测。
