Imaging the neuronal and metabolic basis of resting state connectivity mapping

描述(申请人提供)：该项目旨在使用先进的体内光学成像和显微技术来研究静息脑中的血流变化，以及不同脑区血流波动同步的意义。功能连接图(FCM)是功能磁共振成像(FMRI)中越来越受欢迎的工具，它利用静息脑血流的同步波动来推断不同区域之间的连接。人们普遍认为FCM捕捉到了大脑网络的一个基本属性，并迅速被用于自闭症、阿尔茨海默氏症、抑郁症和精神分裂症等复杂疾病的研究。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，但人们对导致脑血液波动的机制以及不同脑区血流动力学同步性的潜在意义知之甚少。事实上，越来越多的证据表明，血流的基线波动有一系列来源，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联系。在这个项目中，我们将优化和扩展我们迄今开发的先进的体内暴露皮质光学成像和显微工具套件，以解决基线成像的主要挑战；必须在不对多次试验进行平均的情况下获取数据，因此必须具有高信噪比，并且必须并行记录所有参数。为此，我们将在大鼠双侧颅窗上开发高速、高分辨率的血流动力学和大容量钙敏感染料的平行成像，以绘制基线血流量和神经元活动之间的关系。我们还将用自发血流动力学映射黄素蛋白(FAD)自发荧光的波动，作为局部氧化代谢的衡量标准，两者都与同步电生理学相辅相成。这些研究将在一系列麻醉状态下进行，并在一小部分清醒动物中进行(目标1)。为了将我们的发现直接与整个大脑的fMRI数据相关联，我们将开发一个系统，用于同时获取大鼠暴露的皮质光学成像和fMRI数据，阐明fMRI信号波动的代谢(FAD)和神经元(Ca~(2+))基础及其与大脑其余部分波动的关系(目标2)。我们将进一步使用体内双光子显微镜对FAD和NADH荧光以及钙敏感染料进行细胞水平的代谢成像，以探索自发血流动力学活动的细胞相关性，同时使用宽视野反射成像的血红蛋白氧合动力学(目标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推断的连接性的本质。我们的结果将具有非常重要的意义，因为它们将为临床fMRI FCM结果的意义提供洞察力，同时也为FCM研究人员提供指导，以避免潜在的神经血管耦合相关的混乱。

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.