Magnetic stimulation is widely used as a medical treatment for neurological diseases. A reduction in the size of magnetic stimulation devices is desirable, however, because the coils are relatively large compared with electrode stimulation devices. Furthermore, in transcranial magnetic stimulation, the exact magnetically evoked areas in the brain and the mechanisms of neural activation are largely unknown. This study aimed to develop a new implantable microcoil device that stimulates the brain locally, on the order of several tens of micrometers, as well as to understand the mechanisms of micromagnetic stimulation‐induced neural activity. First, to investigate the effects of microcoil shape on neural activation, the induced electric fields of semicircular microcoils with different diameters were calculated numerically in a microcoil model using the standard finite element method. Next, on the basis of the obtained numerical results from the microcoil model with different diameters, we compared the spatial properties of the possible activated areas in neural tissue and examined the most effective microcoil shape for neural activation. Finally, we measured microcoil‐evoked responses using autofluorescent flavoprotein imaging of the mouse brain in vivo, evaluated the validity of our proposed microcoil devices, and discussed possible future improvements for a chronic implant. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

中文翻译：

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微线圈感应电场的数值分析和小鼠大脑体内磁刺激的评估

磁刺激被广泛用作神经系统疾病的药物治疗。然而，期望减小磁刺激装置的尺寸，因为与电极刺激装置相比，线圈相对较大。此外，在经颅磁刺激中，大脑中确切的磁诱发区域和神经激活机制尚不清楚。这项研究旨在开发一种新型的可植入微线圈设备，该设备可在几十微米的数量级上局部刺激大脑，并了解微磁刺激诱导的神经活动的机制。首先，研究微线圈形状对神经激活的影响，采用标准有限元方法，在微线圈模型中数值计算了不同直径的半圆形微线圈的感应电场。接下来，基于从具有不同直径的微线圈模型获得的数值结果，我们比较了神经组织中可能的激活区域的空间特性，并检查了用于神经激活的最有效的微线圈形状。最后，我们使用小鼠大脑的自体荧光黄素蛋白成像测量了微线圈诱发的反应在体内，评估了我们提出的微线圈装置的有效性，并讨论了慢性植入物未来可能的改进。©2020日本电气工程师学会。由Wiley Periodicals LLC发布。