Direct MRI Mapping of Neuronal Magnetic Fields in the Human Brain

描述（由申请人提供）：人脑神经元磁场的直接MRI成像功能MRI技术极大地增强了我们对人脑功能组织的了解。然而，目前使用的功能磁共振成像技术依赖于测量区域脑血流动力学来推断神经活动，而不是直接检测神经元活动。这种间接测量有几个局限性。首先，局部脑血流动力学不一定总是反映神经元活动，并且可能在没有潜在神经元活动改变的情况下发生变化（例如，药物作用）。其次，血管的几何形状可能并不总是与神经放电区域重叠，因此局部脑血流动力学的调解可能会降低空间定位。第三，脑血流动力学反应（秒）比神经元放电（毫秒）慢得多。因此，相对于潜在的神经激活，血流动力学测量的时间分辨率是有限的和降低的。为了解决当前功能磁共振成像技术的不足，我们在2003年报道了一种新的功能磁共振成像技术，磁源MRI (msMRI)，用于直接评估神经元功能。该技术是基于直接检测MRI信号的变化，以响应伴随神经元放电的磁场变化，并提供改进的空间定位和时间分辨率。虽然它提供了希望，但msMRI仍处于早期发展阶段。有争议的结果被报道。这一发展建议的总体目标是研究msMRI信号对比的机制，并澄清争议。将进行理论建模，研究msMRI的机制和msMRI信号的特征时空特征（ai1）。我们将研究msMRI信号的特征时间特征，证明msMRI具有高时间分辨率，可以准确地检测刺激开始和抵消的时间（Aim2）。通过展示相位和幅度图像（Aim3）的独特和不同的空间分布，将研究msMRI信号的特征空间特征。将探索msMRI信号与实验参数之间的独特关系（Aim4）。最后，将研究msMRI信号对对称SE序列的不同灵敏度（Aim5）。当前项目的成功完成将增强我们对msMRI信号对比机制的理解；澄清围绕核磁共振检测的争议；并为msMRI技术的未来开发、优化和应用提供坚实的背景。公共卫生相关性：本发展建议的总体目标是研究磁源磁共振成像（msMRI）中的信号对比机制，并开发用于绘制人脑功能的msMRI程序。当前项目的成功完成将增强我们对msMRI信号对比机制的理解；澄清围绕核磁共振检测的争议；并为msMRI技术的未来开发、优化和应用提供坚实的背景

DESCRIPTION (provided by applicant): Direct MRI mapping of neuronal magnetic fields in the human brain Functional MRI technique has greatly enhanced our understanding of the functional organization of the human brain. Currently used fMRI techniques, however, depend on measuring regional cerebral hemodynamics to infer neural activation, rather than detecting neuronal activity directly. This indirect measurement has several limitations. First, regional cerebral hemodynamics does not necessarily always reflect neuronal activity and could change (for example, drug effects) without underlying neuronal activity change. Second, vascular geometry may not always overlap with the area of neural firing, so that the mediation of regional cerebral hemodynamics may degrade spatial localization. Third, the cerebral hemodynamics responses are much slower (seconds) than neuronal firing (milliseconds). Temporal resolution of the hemodynamic measurement is, therefore, limited and downgraded with respect to the underlying neural activation. To address shortcomings of current fMRI techniques, we reported a novel fMRI technique, magnetic source MRI (msMRI), for directly assessing neuronal function at 2003. The technique is based on directly detecting MRI signal changes in response to the changes in magnetic fields concomitant with neuronal firing and offers improved spatial localization and temporal resolution. While it offers promise, msMRI is still at its early developmental stage. Controversial results have been reported. The overall objectives of this developmental proposal are then to study mechanisms of signal contrast in msMRI and to clarify the controversies. Theoretical modeling will be performed to study mechanisms of msMRI and characteristic spatial and temporal signatures of msMRI signals (Aim1). The characteristic temporal signature of msMRI signals will be investigated by demonstrating that msMRI has high temporal resolution and can accurately detect the timing of both stimulation onset and offset (Aim2). Characteristic spatial signatures of msMRI signal will be investigated by demonstrating unique and different spatial distributions for phase and magnitude images (Aim3). Unique relationships between msMRI signals and experimental parameters will be explored (Aim4). Finally, the distinct sensitivity of msMRI signals to a symmetry SE sequence will be investigated (Aim5). Successful completion of the current project will enhance our understanding of mechanisms of signal contrast in msMRI; clarify the controversy surrounding msMRI detections; and provide a solid background for future developments, optimizations, and applications of the msMRI technique. PUBLIC HEALTH RELEVANCE: The overall objectives of this developmental proposal are to study mechanisms of signal contrast in magnetic source magnetic resonance imaging (msMRI) and to develop msMRI procedures for mapping human brain functions. Successful completion of the current project will enhance our understanding of mechanisms of signal contrast in msMRI; clarify the controversy surrounding msMRI detections; and provide a solid background for future developments, optimizations, and applications of the msMRI technique