Direct Imaging of Neural Currents using Ultra-Low Field Magnetic Resonance Techni

使用超低场磁共振技术直接成像神经电流

• 批准号: 7139534
• 负责人: John Compton Mosher
• 金额: $ 45.9万
• 依托单位: LOS ALAMOS NAT SECTY-LOS ALAMOS NAT LAB
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-11 至 2009-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7139534
• 关键词: brain; clinical research; human; hydrogen ions; magnetic field; magnetism; measurement; model; motivation; relaxation; sectioning; tissues

DESCRIPTION (provided by applicant): We propose to demonstrate the feasibility of using nuclear magnetic resonance (NMR) techniques at ultra- low fields (ULF) to directly image neuronal currents in the human brain. We hypothesize that neuronal currents (both intra- and extra-cellular) will interact with the proton spins in tissue resulting in a measurable change in the NMR signal that can be imaged with existing magnetic resonance imaging (MRI) techniques at ULF. This proposal is in response to RFA-EB-05-001: "New Ways to Image Neural Activity." MRI spatially encodes the NMR signature of nuclei, typically protons, in a volume of interest. Today's high-field (HF) MRI machines employ static magnetic fields in the 1.5 T to above 9 T range to yield exquisite anatomical features. The last decade has also witnessed an explosion in functional MRI (fMRI) research that measures hemody- namic responses; however, as this RFA notes, such responses are relatively sluggish and only indirectly related to electrophysiological processes. Magnetoencephalography (MEG) and electroencephalography (EEG) are direct measures of the external magnetic and electric fields generated by neuronal currents. While these modalities yield detailed temporal information, the spatial localization must be inferred from highly-spe-cific spatial modeling priors. The electrophysiological "imaging" in MEG and EEG is therefore only "indirect" at best. Recently, several researchers proposed that electrophysiological.activity may interact with the nuclear spins in a measurable manner, such as causing phase and amplitude variations or changing the rate of decay in the NMR signal. Interactions between neuronal currents and spin populations in tissue may enable direct neuronal imaging (DNI) by MRI. Most studies to date have focussed on the feasibility of DNI at HF. Recently, our group (and a few others) has experimentally demonstrated ultra-low field (ULF) MRI, using fields 100,000- 1,000,000 times weaker than HF-MRI. While the NMR signals, known as the free induction decay (FID), at ULF are dramatically weaker than HF, we acquired high signal-to-noise measurements of FIDs at ULF using super- conducting .quantum interference device (SQUID) technology. We also recently presented the world's first simultaneous FID and MEG measurement of the human brain, using SQUID sensors. Our research will pursue demonstrating the feasibility of measuring a neuronal current effect on the NMR signature at ULF using two distinct approaches: 1) we will study interactions between neuronal currents and the proton spin population in tissue that induce dephasing of the spin population; and 2) we will study a novel mechanism based on the interaction of neuronal currents and the spin population that will cause a distinctly different relaxation of the spin population. The first approach is a direct extension of ideas presented for DNI at high fields, but can be greatly enhanced at ULF. Our second approach pursues an exciting possibility unique to ULF.

描述（由申请人提供）： 我们建议证明在超低场（ULF）在人脑中使用核磁共振（NMR）技术的可行性。我们假设神经元电流（细胞内和细胞外）将与组织中的质子旋转相互作用，从而导致NMR信号的可测量变化，而NMR信号可以通过ULF的现有磁共振成像（MRI）技术进行成像。该建议是对RFA-EB-05-001的回应：“图像神经活动的新方法”。 MRI在空间上编码了核（通常是质子）的NMR特征，其中有质子的含量。当今的高场（HF）MRI机器在1.5 t至9 t范围内采用静态磁场，以产生精美的解剖学特征。在过去的十年中，还见证了功能性MRI（fMRI）研究的爆炸式爆炸，该研究衡量了血液的反应。但是，正如RFA所指出的那样，这种反应相对迟钝，仅间接与电生理过程有关。磁脑电图（MEG）和脑电图（EEG）是神经元电流产生的外部磁和电场的直接测量。尽管这些模式产生了详细的时间信息，但必须从高度分离的空间建模先验中推断出空间定位。因此，MEG和EEG中的电生理“成像”充其量仅是“间接”。最近，一些研究人员提出电生理。活动可能以可测量的方式与核自旋相互作用，例如引起相和振幅变化或改变NMR信号中衰减的速率。在组织中神经元电流与旋转种群之间的相互作用可以通过MRI实现直接的神经元成像（DNI）。迄今为止，大多数研究都集中在HF上DNI的可行性上。最近，我们的小组（以及其他一些）在实验上证明了超低场（ULF）MRI，使用比HF-MRI弱100,000-1,000,000倍。虽然ULF的NMR信号（称为自由感应衰减（FID））比HF弱弱，但我们使用Super-Toctioning .Quantum Interfection .Quantum Interference（Squid）技术获得了ULF的高信噪比测量。我们最近还使用鱿鱼传感器介绍了世界上第一个同时的FID和MEG对人脑的测量。我们的研究将通过两种不同的方法来证明测量ULF NMR签名的神经元电流影响的可行性：1）我们将研究神经元电流与组织中质子自旋种群之间的相互作用，从而诱导自旋种群的延迟； 2）我们将根据神经元电流的相互作用和自旋种群的相互作用研究一种新的机制，这将导致自旋种群的松弛截然不同。第一种方法是直接扩展在高领域为DNI提出的想法，但在ULF可以大大提高。我们的第二种方法追求了ULF独有的激动人心的可能性。