Investigation of MR signal modulation due to magnetic fields from neuronal currents in the adult human optic nerve and visual cortex
Investigation of MR signal modulation due to magnetic fields from neuronal currents in the adult human optic nerve and visual cortex
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DOI：
10.1016/j.mri.2006.01.005
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发表时间：
2006-07-01
影响因子：
2.5
通讯作者：
Paley, Martyn N. J.
中科院分区：
文献类型：
--
作者：
Chow, Li Sze;Cook, Greg G.;Paley, Martyn N. J.
神经元电流产生微弱的瞬态磁场，这里正在研究的假设是，这些与B-0场平行的组件可能会调制MR信号，从而提供一种直接检测神经冲动的方法。磁流变信号的相位和幅度随时间变化的理论，由于所有的外部磁场已经发展预测这种调制。实验中，快速梯度回波EPI序列（TR = 158 ms）。TE=32.4 ms)试图直接检测成人视神经和视觉皮层中的这些神经元电流，使用280毫米的正交头线圈，在1.5 t下，一个对称的体素内场分布，可以合理地假设视神经和视觉皮层的轴突场。会导致体素内的相位抵消，因此，只有幅度变化是预期的。在另一片土地上。所有不对称的体素内场分布都会产生相位和振幅变化。活体图像数据集显示神经放电的检出率为56%，而相位图像数据集的检出率为零。相对于完全放松的平衡信号，信号的幅度变化百分比落在预测的RMS范围内，视神经为1.2-2.1 nT，视觉皮层为0.4-0.6 nT。根据轴突场在体素内产生对称洛伦兹场分布的假设。(C) 2006爱思唯尔公司版权所有。
Neuronal currents produce weak transient magnetic fields, and the hypothesis being investigated here is that the components of these parallel to the B-0 field call potentially modulate the MR signal, thus providing a means of direct detection of nerve impulses. A theory for the phase and amplitude changes of the MR signal over time due to ail external magnetic field has been developed to predict this modulation. Experimentally, a fast gradient-echo EPI sequence (TR = 158 ms. TE=32.4 ms) was employed in an attempt to directly detect these neuronal currents in the adult human optic nerve and visual cortex using a 280-mm quadrature head coil at 1.5 T. A symmetrical intravoxel field distribution, which can be plausibly hypothesized for the axonal fields in the optic nerve and visual cortex. would result in phase cancellation within a voxel, and hence, only amplitude changes would be expected. On the other]land. ail asymmetrical intravoxel field distribution would produce both phase and amplitude changes. The in vivo magnitude image data sets show a significant nerve firing detection rate of 56%, with zero detection using the phase image data sets. The percentage magnitude signal changes relative to the fully relaxed equilibrium signal fall within a predicted RMS field range of 1.2-2.1 nT in the optic nerve and 0.4-0.6 nT in the visual cortex. according to the hypothesis that the axonal fields create a symmetrical Lorentzian field distribution within the voxel. (C) 2006 Elsevier Inc. All rights reserved.