Imaging the neuronal and metabolic basis of resting state connectivity mapping

项目描述（由申请人提供）：本项目旨在利用先进的体内光学成像和显微镜技术研究静息脑血流变化，以及脑不同区域血流波动同步的意义。功能连接映射（FCM）是功能磁共振成像（fMRI）中日益流行的工具，它利用整个静息大脑血流的同步波动来推断不同区域之间的连接。FCM被广泛认为捕获了大脑网络的基本特性，并迅速被用于研究复杂疾病，如自闭症、阿尔茨海默氏症、抑郁症和精神分裂症。然而，尽管FCM越来越多地被应用于传统的基于刺激的fMRI研究，但人们对引起脑血波动的机制知之甚少，也不了解不同脑区血流动力学同步的潜在意义。事实上，越来越多的证据表明，血流量的基线波动有一系列的起源，可能并不都与神经元活动的存在有关，也不代表大脑区域之间的真正连接。在这个项目中，我们将优化和扩展我们迄今为止开发的先进体内暴露皮质光学成像和显微镜工具套件，以解决基线成像的主要挑战；该数据必须在不经过多次试验平均的情况下获得，因此必须具有高信噪比，并且所有参数必须并行记录。为此，我们将在大鼠双侧大颅窗上开发高速、高分辨率的血流动力学和大容量钙敏感染料并行成像，以绘制基线血流和神经元活动之间的关系。我们还将绘制黄素蛋白（FAD）自身荧光的波动与自发血流动力学作为局部氧化代谢的测量，两者都辅以同步的电生理学。这些研究将在一系列麻醉状态下以及一小部分清醒动物中进行（目的1）。为了将我们的发现直接与全脑的功能磁共振成像数据联系起来，我们将开发一种系统，用于同时获取大鼠暴露的皮质光学成像和功能磁共振成像数据，阐明功能磁共振成像信号波动的代谢（FAD）和神经元（Ca2+）基础及其与大脑其他部分波动的关系（目的2）。我们将进一步使用体内双光子显微镜进行FAD和NADH荧光的细胞水平代谢成像，以及钙敏感染料，以探索自发血流动力学活动的细胞相关性，同时进行血红蛋白氧合动力学的宽视场反射成像（目的3）。这些创新的研究将使我们能够确定自发的血流动力学波动是否与刺激诱发的反应具有相同的潜在基础，并探索FCM推断的连通性的本质。我们的结果将是非常重要的，因为它们将提供临床fMRI FCM结果的意义，同时也为FCM研究人员如何避免潜在的神经血管耦合相关混淆提供指导。

DESCRIPTION (provided by applicant): This project aims to use advanced in-vivo optical imaging and microscopy techniques to study blood flow variations in the resting brain, and the meaning of synchronizations in blood flow fluctuations in different brain regions. Functional connectivity mapping (FCM) is an increasingly popular tool in functional magnetic resonance imaging (fMRI), which harnesses synchronous fluctuations in blood flow throughout the resting brain to infer connectivity between different regions. FCM is widely thought to capture a fundamental property of the brain's networks, and is rapidly being adopted for studies of complex conditions such as autism, Alzheimer's, depression and schizophrenia. However, while FCM is increasingly being applied in preference to traditional stimulation-based fMRI studies, very little is understood about the mechanisms causing the fluctuations in cerebral blood, nor the underlying meaning of hemodynamic synchrony in different brain areas. In fact, there is mounting evidence that baseline fluctuations in blood flow have a range of origins that may not all be related to the presence of neuronal activity, nor represent genuine connectivity between brain regions. In this project, we will optimize and extend the suite of advanced in-vivo exposed-cortex optical imaging and microscopy tools that we have developed to date to address the primary challenge of baseline imaging; that data must be acquired without averaging over multiple trials and therefore must have high signal to noise, and all parameters must be recorded in parallel. To this end, we will develop high-speed, high resolution parallel imaging of both hemodynamics and bulk-loaded calcium sensitive dyes over large bilateral cranial windows in rats to map the relations between baseline blood flow and neuronal activity. We will also map fluctuations in flavoprotein (FAD) autofluorescence with spontaneous hemodynamics as a measure of local oxidative metabolism, both complemented with simultaneous electrophysiology. These studies will be performed under a range of anesthesia states as well as in a small subset of awake animals (aim 1). To relate our findings directly to fMRI data in the whole brain, we will develop a system for simultaneous acquisition of exposed cortex optical imaging and fMRI data in rats, elucidating the metabolic (FAD) and neuronal (Ca2+) basis of fMRI signal fluctuations and their relation to fluctuations in the rest of the brain (aim 2). We will further use in-vivo two-photon microscopy for cellular-level metabolic imaging of FAD and NADH fluorescence, and of calcium sensitive dyes to explore the cellular correlates of spontaneous hemodynamic activity, with simultaneous wide-field reflectance imaging of hemoglobin oxygenation dynamics (aim 3). These innovative studies will allow us to determine whether spontaneous hemodynamic fluctuations have the same underlying basis as stimulus-evoked responses, and to explore the nature of the connectivity that FCM infers. Our results will be highly significant, as they will provide insight into the meaning of clinical fMRI FCM results, while also providing guidance for FCM researchers in how to avoid potential neurovascular coupling-related confounds.