BACKGROUND The neurophysiological effects of transcranial direct current stimulation (tDCS) are typically described with respect to changes in cortical excitability, defined by using transcranial magnetic stimulation pulses to determine changes in motor evoked potentials. However, how individual cortical neurons change firing patterns under the influence of tDCS is largely unknown. While the relatively weak currents produced in the brain by tDCS may not be adequate to directly depolarize neuronal membranes, ongoing neuronal activity, combined with subthreshold changes in membrane polarization might be sufficient to alter the threshold for neural firing. OBJECTIVES The purpose of this study was to determine the effects of tDCS on neurophysiological activity in motor cortex of freely moving, healthy rats. METHODS In nine healthy, ambulatory rats, each studied under six different stimulation conditions varying in current intensity (maximum current density = 39.8 A/m2 at 0.4 mA) and polarity (anodal or cathodal), neural activity was analyzed in response to 20 minutes of tDCS applied through bone screws insulated from the overlying scalp. RESULTS After analysis of 480 multi-unit channels that satisfied a rigid set of neurophysiological criteria, we found no systematic effect of tDCS stimulation condition on firing rate or firing pattern. Restricting the analysis to the most responsive units, subtle, but statistically significant changes occurred only in the highest intensity anodal condition. CONCLUSIONS These results confirm that at current densities typically used in human or animal tDCS studies, observed effects of tDCS are likely to occur via mechanisms other than direct neuronal depolarization.

中文翻译：

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tDCS 对健康动态大鼠模型自发性尖峰活动的影响

背景技术经颅直流电刺激（tDCS）的神经生理学效应通常根据皮质兴奋性的变化来描述，通过使用经颅磁刺激脉冲来确定运动诱发电位的变化来定义。然而，个体皮质神经元如何在 tDCS 的影响下改变放电模式在很大程度上是未知的。虽然 tDCS 在大脑中产生的相对较弱的电流可能不足以直接使神经元膜去极化，但持续的神经元活动，结合膜极化的亚阈值变化可能足以改变神经放电的阈值。目的 本研究的目的是确定 tDCS 对自由运动的健康大鼠运动皮层神经生理活动的影响。方法 在 9 只健康的走动大鼠中，每个在电流强度（最大电流密度 = 39.8 A/m2，0.4 mA）和极性（阳极或阴极）不同的六种不同刺激条件下进行研究，响应通过与电极绝缘的接骨螺钉施加 20 分钟的 tDCS 来分析神经活动。覆盖头皮。结果 在对满足一组严格神经生理学标准的 480 个多单元通道进行分析后，我们发现 tDCS 刺激条件对放电率或放电模式没有系统影响。将分析限制在最敏感的单元中，细微但统计上显着的变化仅发生在最高强度的阳极条件下。结论 这些结果证实，在人类或动物 tDCS 研究中通常使用的电流密度下，