BIOPHYSICAL BASIS OF PHYSIOLOGICAL FLUCTUATIONS IN FMRI

本提案的长期目标是使用功能性 磁共振成像（fMRI），以获得更好的理解 脑血流和氧合时空自发波动 在休息时大脑的功能区域。功能磁共振成像被广泛用于 绘制健康受试者的感觉、运动和认知功能， 脑肿瘤、神经心理疾病和脑血管疾病患者 疾病一般的方法是给受试者呈现一个运动的，感觉的， 或认知任务，并绘制相对于控制状态的激活区域。 该小组最近证明，低频波动存在于 休息的人脑可能反映神经元活动， 与脑血流自发波动的特征相似 和在动物模型中观察到的组织PO2。他们发现了 这些低频波动之间的功能相关的区域， 人类大脑和功能连接图。在中度 呼吸性高碳酸血症，MR中低频波动的幅度 信号强度可逆地减弱，如在先前的研究中所观察到的。 动物实验，导致时间相关性降低， 在感觉运动皮层的半球内和半球间。其工作 生理波动引起静息状态假说 功能连接图在本质上类似于任务激活 信号，它们来自神经元活动和代谢的波动， 需求该项目的具体目标是：（1）确定生物物理 静息态脑血流自发低频波动的基础 使用人类受试者和动物模型，（2） 测试一个假设，即在给定的大脑区域的生理波动， 可以被分解成两个或更多个波形， 时间相关模式，（3）确定对注意力的依赖性 皮层区域之间的时间相关性的强度，以及（4） 开发可靠和强大的算法来检测任务诱导信号 在空间变化的低频生理存在的变化 波动这项研究旨在提高对 血流动力学的时间相关性存在于休息的人脑和奠定 为未来与健康和 患病的人类实验对象

The long-term objective of this proposal is to use functional magnetic resonance imaging (fMRI) to obtain an improved understanding of spatio-temporal spontaneous fluctuations in cerebral flow and oxygenation within functionally defined brain regions during rest. fMRI is widely used to map sensory, motor, and cognitive functions in healthy subjects as well as patients with brain tumors, neuropsychological disease, and cerebrovascular disease. The general approach is to present the subject with a motor, sensory, or cognitive task and map regions of activation relative to the control state. The group has recently demonstrated that low-frequency fluctuations exist in the resting human brain that may reflect neuronal activity and that show similar characteristics to the spontaneous fluctuations of cerebral blood flow and tissue p02 observed in animal models. They found temporal correlation of these low-frequency fluctuations between functionally-related regions of the human brain, and functional connectivity maps were produced. During moderate respiratory hypercapnia, the magnitude of low-frequency fluctuations in the MR signal intensity was reversibly diminished, as has been observed in previous animal experiments, resulting in a decrease of the temporal correlation both within and across hemispheres of the sensorimotor cortex. Their working hypothesis that physiological fluctuations that give rise to resting-state functional connectivity maps are similar in nature to the task-activation signal and that they arise from fluctuations in neuronal activity and metabolic demand. The specific aims of the project are: (1) to determine the biophysical basis of resting-state spontaneous low-frequency fluctuations of cerebral blood flow and blood oxygenation using both human subjects and animal models, (2) to test the hypothesis that physiological fluctuations in a given brain region can be decomposed into two or more waveforms that exhibit different spatial patterns of temporal correlation, (3) to determine the dependence on attention of the strength of the temporal correlation between cortical regions, and (4) to develop reliable and robust algorithms for detecting task-induced signal changes in the presence of spatially varying low-frequency physiological fluctuations. This research is designed to improve the understanding of the hemodynamic temporal correlations present in the resting human brain and to lay the foundation for future work related to brain function in both healthy and diseased human subjects.