Neurophysiological Basis of fMRI

描述(申请人提供)：功能磁共振成像(FMRI)有望在完好无损的受试者的正常操作过程中，提供精确定位和跟踪潜在感觉、运动和认知技能的大脑活动模式的能力。然而，由于我们对神经活动和fMRI信号之间的联系了解不足，以及当前fMRI方法的固有局限性，这一前景受到了阻碍。我们将通过将高场fMRI与神经集合电生理学和药理学相结合的实验来研究fMRI信号的神经基础；fMRI将使用高分辨率、高信噪比的7-TESLA系统，采用BOLD和灌注敏感方案进行。电生理学将利用头皮ERP记录和线性阵列多电极的深度记录，并将重点放在ERP和电流源密度(CSD)测量以及动作电位上。尤其是CSD措施，对于将神经活动和功能磁共振联系起来是必不可少的。神经化学操作将需要全身输液和皮质内微量输液。我们的具体目标是： 1.确定BOLD-fMRI的神经关联： 2.优化fMRI的空间和时间分辨率 3.确定fMRI与ERPs及脑过程的关系。 初步研究将在麻醉的猕猴身上进行，重点是3b区的手部皮质。后来的研究将在清醒的猴子身上实施，并将扩展到几个额外的皮质区域。这些研究将产生有用的副产品，准确描述猕猴手部体感上升通路的时空激活模式，并使用与人类使用的方法直接比较的方法来实现这一点。这将有助于弥合猴子庞大的单一单位文献和对人类体感结构和功能的不断发展的理解之间的差距。

DESCRIPTION (provided by applicant): Functional magnetic resonance imaging (fMRI) promises to provide the ability to pinpoint and track brain activity patterns underlying sensory, motor and cognitive skills, during their normal operation in intact subjects. However, this promise is thwarted by our inadequate understanding of the linkage between neural activity and fMRI signals, and by inherent limitations of current fMRI methods. We will investigate the neural basis of fMRI signals through experiments that combine high field fMRI with neural ensemble electrophysiology and pharmacology in monkeys; fMRI will be conducted with BOLD- and perfusion-sensitive protocols using a high-resolution, high signal-to-noise 7-Tesla system. Electrophysiology will utilize both scalp ERP recordings, and depth recordings with linear array multielectrodes, and will focus on ERP and current source density (CSD) measures as well as action potentials. CSD measures in particular, are essential for linking neural activity and fMRI. Neurochemical manipulation will entail both systemic infusions and intracortical microinfusions. Our specific aims are: 1. To Identify Neural Correlates of BOLD-fMRI: 2. To Optimize the Spatial and Temporal Resolution of fMRI 3. To Determine the Relationship of fMRI to ERPs and to Brain Processes. Initial studies will be conducted in anesthetized macaque monkeys & will focus on the cortical hand representation in Area 3b. Later studies will be implemented in awake monkeys & will be expanded to a few additional cortical regions. These studies will have the useful by-product of accurately describing the spatiotemporal activation pattern of the ascending somatosensory pathways from the hand surface in the macaque, and of doing so with methods that directly compare to those used in humans. This will help to bridge-the-gap between a vast single unit literature in monkeys, and a developing understanding of somatosensory structure and function in humans.