BIOPHYSICAL BASIS OF PHYSIOLOGICAL FLUCTUATIONS IN FMRI

该提案的长期目标是使用功能 磁共振成像(FMRI)以更好地了解 脑血流和氧合的时空自发波动 在休息时在大脑功能区域内。功能磁共振成像被广泛用于 绘制健康受试者的感觉、运动和认知功能图 脑肿瘤、神经心理疾病和脑血管疾病患者 疾病。一般的方法是向受试者呈现一种运动、感觉、 或认知任务，并绘制与控制状态相关的激活区域。 该小组最近证明了低频波动存在于 静息的人类大脑可以反映神经元的活动，这表明 与脑血流自发性波动相似的特征 在动物模型中观察到组织P02。他们发现时间上的相关性 这些功能相关区域之间的低频波动 人类大脑，并制作了功能连接图。在中级期间 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，正如在以前的 动物实验，导致两者的时间相关性降低 在感觉运动皮质的两个半球内和两个半球之间。他们的工作 假设引起静息状态的生理波动 功能连接图在本质上类似于任务激活 它们是由神经元活动和代谢的波动引起的 需求。该项目的具体目标是：(1)确定生物物理 静息状态下脑血自发低频波动的基础 使用人类受试者和动物模型的血流和血液氧合，(2)到 测试假设，即给定大脑区域的生理波动可以 被分解成两个或更多呈现不同空间的波形 时间相关模式，(3)确定对注意的依赖性 皮质区域之间的时间相关性的强度，以及(4) 开发可靠和健壮的算法来检测任务诱导信号 空间变化的低频生理信号的存在变化 波动。这项研究的目的是为了提高对 静息状态下人脑和蛋鸡的血流动力学时间相关性 为未来与健康和健康的大脑功能相关的工作奠定基础 患病的人类受试者。

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.