Current density threshold for the stimulation of neurons in the motor cortex area
Current density threshold for the stimulation of neurons in the motor cortex area
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DOI：
10.1002/bem.10036
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发表时间：
2002-09-01
影响因子：
1.9
通讯作者：
Buchner, H
中科院分区：
文献类型：
--
作者：
Kowalski, T;Silny, J;Buchner, H
本研究的目的是确定一个电流密度阈值，兴奋运动皮层区的大脑。在文献中发现，在低于1 kHz的频率下，神经纤维（直径为20 μ m）兴奋的电流密度阈值约为1 A/m（2）。考虑到安全系数为100，国际非电离辐射防护委员会（ICNIRP）建议将暴露量限制在0.01 A/m（2）。运动皮层中神经元的电磁刺激通过磁或电经颅刺激用于神经损伤和神经病的临床诊断。结合来自临床研究的医学数据和Magstim（R）Model 200刺激器的技术规格，我们能够通过有限元法（FEM）计算用于激励人类运动皮层的电流密度阈值。基于磁共振成像（MRI）切片构建3D-CAD头部模型，并将其分割为具有不同电导率的四个解剖结构（头皮、颅骨、大脑和脑室系统）。计算出在2.44 kHz和50 Hz下刺激上肢运动皮层区域的电流密度阈值分别为6和2.5 A/m（2）。由于这些值比推荐的ICNIRP值高出两个数量级，因此不需要降低大脑刺激的安全标准。
The aim of this study was to determine a current density threshold for exciting the motor cortex area of the brain. The current density threshold for excitation of nerve fibres (20 pm in diameter) found in the literature is approximately 1 A/m(2) at frequencies lower than 1 kHz. In consideration of a safety factor of 100, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommends to restrict the exposure to 0.01 A/m(2). The electromagnetic stimulation of neurons in the motor cortex is used in the clinical diagnosis of nerve lesions and neuropathy by means of magnetic or electrical transcranial stimulation. Combining medical data from clinical studies and technical specifications of the Magstim(R) Model 200 stimulator, we were able to compute the current density threshold for the excitation of the human motor cortex by means of the finite element method (FEM). A 3D-CAD head model was built on the basis of magnetic resonance imaging (MRI) slices and segmented into four anatomical structures (scalp, skull, brain, and ventricular system) with different conductivities. A current density threshold for the stimulation of the motor cortex area of the upper limbs of 6 and 2.5 A/m(2) at 2.44 kHz and 50 Hz, respectively, was calculated. As these values lie above the recommended ICNIRP values by two orders of magnitude there is no need for lower safety standards with regard to stimulation of the brain.