Kar Kohitij, Duijnhouwer Jacob, Krekelberg Bart
Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, New Jersey 07102
Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, New Jersey 07102.
J Neurosci. 2017 Mar 1;37(9):2325-2335. doi: 10.1523/JNEUROSCI.2266-16.2016. Epub 2017 Jan 30.
We previously showed that brief application of 2 mA (peak-to-peak) transcranial currents alternating at 10 Hz significantly reduces motion adaptation in humans. This is but one of many behavioral studies showing that weak currents applied to the scalp modulate neural processing. Transcranial stimulation has been shown to improve perception, learning, and a range of clinical symptoms. Few studies, however, have measured the neural consequences of transcranial current stimulation. We capitalized on the strong link between motion perception and neural activity in the middle temporal (MT) area of the macaque monkey to study the neural mechanisms that underlie the behavioral consequences of transcranial alternating current stimulation. First, we observed that 2 mA currents generated substantial intracranial fields, which were much stronger in the stimulated hemisphere (0.12 V/m) than on the opposite side of the brain (0.03 V/m). Second, we found that brief application of transcranial alternating current stimulation at 10 Hz reduced spike-frequency adaptation of MT neurons and led to a broadband increase in the power spectrum of local field potentials. Together, these findings provide a direct demonstration that weak electric fields applied to the scalp significantly affect neural processing in the primate brain and that this includes a hitherto unknown mechanism that attenuates sensory adaptation. Transcranial stimulation has been claimed to improve perception, learning, and a range of clinical symptoms. Little is known, however, how transcranial current stimulation generates such effects, and the search for better stimulation protocols proceeds largely by trial and error. We investigated, for the first time, the neural consequences of stimulation in the monkey brain. We found that even brief application of alternating current stimulation reduced the effects of adaptation on single-neuron firing rates and local field potentials; this mechanistic insight explains previous behavioral findings and suggests a novel way to modulate neural information processing using transcranial currents. In addition, by developing an animal model to help understand transcranial stimulation, this study will aid the rational design of stimulation protocols for the treatment of mental illnesses, and the improvement of perception and learning.
我们之前的研究表明，以10赫兹频率交替施加2毫安（峰峰值）的经颅电流，能显著降低人类的运动适应性。这只是众多行为学研究中的一项，表明施加于头皮的弱电流可调节神经加工过程。经颅刺激已被证明能改善感知、学习以及一系列临床症状。然而，很少有研究测量经颅电流刺激的神经后果。我们利用猕猴颞中区（MT）区域中运动感知与神经活动之间的紧密联系，来研究经颅交流电刺激行为后果背后的神经机制。首先，我们观察到2毫安的电流产生了大量颅内电场，刺激半球的电场强度（0.12伏/米）比大脑另一侧（0.03伏/米）要强得多。其次，我们发现以10赫兹频率短暂施加经颅交流电刺激，会降低MT神经元的放电频率适应性，并导致局部场电位功率谱的宽带增加。这些发现共同提供了一个直接证据，即施加于头皮的弱电场会显著影响灵长类大脑中的神经加工过程，且这包括一种迄今未知的减弱感觉适应的机制。经颅刺激据称能改善感知、学习以及一系列临床症状。然而，对于经颅电流刺激如何产生这些效果知之甚少，目前寻找更好刺激方案的过程很大程度上是通过反复试验。我们首次研究了猴子大脑中刺激的神经后果。我们发现，即使是短暂施加交流电刺激，也会降低适应对单神经元放电率和局部场电位的影响；这种机制性的见解解释了先前的行为学发现，并提出了一种利用经颅电流调节神经信息处理的新方法。此外，通过建立一个有助于理解经颅刺激的动物模型，本研究将有助于合理设计用于治疗精神疾病以及改善感知和学习的刺激方案。
