Functional Connectivity Network in default mode regions provides the underlying infrastructure for task-based functional co-de/activation networks

摘要 最近的发展表明，大脑通过许多大规模的 正常运行的子系统或网络。研究最多的大脑网络之一是默认模式网络 然而，债务管理网络的内部结构及其如何履行其职能仍然令人费解。 DMN的地形是使用四种不同的成像技术绘制的：通过减少 以~(150)O-PET为静息高代谢区研究任务投入时DMN区的血流 使用FDG-PET；使用BOLD-fMRI作为基于任务的去激活；以及通过 静息状态功能磁共振成像。在15O-PET研究中观察到的基于任务的血流减少，以及基于任务的 使用BOLD-FMRI观察到的失活似乎反映了相同的神经生理过程， 因为大胆的信号与血液流动高度混淆。也有人假设静息状态的功能 DMN区域的连接和高代谢反映了相同的神经生理过程；因此 结论：静息状态的功能连通性是对大脑的基线、内在或 休息状态的活动。然而，最近的证据表明，这种可能性受到了质疑 静息状态的功能连接网络在麻醉、睡眠甚至任务执行期间都是活跃的。 这些发现提出了一个关键但尚未得到回答的问题：这种重叠网络的作用是什么 在DMN地区？我们假设DMN区域的功能连通性代表较低的 级别进程，为执行以下任务的更高级别网络提供底层基础设施 实际功能。 据报道，DMN区域的功能连接和基于任务的停用 与正常衰老、阿尔茨海默病临床前阶段、轻度认知障碍和 阿尔茨海默氏症。然而，由于现场的假设是DMN的功能连通性和 基于任务的去激活是相同的潜在神经生理过程的代表，已经有 据我们所知，没有研究调查功能连通性或负性事件的级联 大胆的回应被打乱了。理清AD中的一连串事件对于理解 疾病的始发、进展和治疗。我们在这个项目中的初步证据表明，强加 基于任务的去激活网络中的改变不会对 同样的地区。目前的提议将使用阿尔茨海默病的无症状阶段来测试 底层功能连接中断会导致对中基于任务的停用进行任何更改 DMN，这是等级结构的证据。

Summary Recent developments demonstrate that the brain carries out its functions through a number of large-scale functional sub-systems, or networks. One of the most studied brain networks is the default mode network (DMN); however, the internal structure of the DMN, and how it carries out its functions, still remains elusive. The topography of the DMN has been mapped using four different imaging techniques: through reductions in the blood flow of DMN regions during task engagement using 15O-PET; as the hypermetabolic regions at rest using FDG-PET; as the task-based deactivation using BOLD-fMRI; and through functional connectivity in resting-state fMRI. The task-based blood-flow reductions observed in 15O-PET studies, and task-based deactivations observed using BOLD-fMRI, seem to be reflective of the same neurophysiological processes, since BOLD signal is highly confounded by blood flow. It has also been postulated that resting-state functional connectivity and hypermetabolism in DMN regions reflect the same neurophysiological process; thus concluding that the resting-state functional connectivity is the measurement of the brain’s baseline, intrinsic, or resting-state activities. However, recent evidence has put such possibility under question by indicating that resting-state functional connectivity networks are active during anesthesia, sleep, and even task-performance. Such findings raise a critical, but as of yet unanswered, question: what is the role of such overlapping networks in DMN regions? We hypothesize that functional connectivity in the DMN regions is representative of a lower level process, which provides the underlying infrastructure for the higher-level network that carries out the actual function. Both functional connectivity and task-based deactivation in the DMN regions have been reported to be disrupted with normal aging, the pre-clinical stage of Alzheimer’s disease, mild cognitive impairment and Alzheimer’s disease. However, since the assumption in the field is that the DMN’s functional connectivity and task-based deactivation are representative of the same underlying neurophysiological process, there has been no study, to our knowledge, investigating the cascade of the events in which functional connectivity or negative BOLD response get disrupted. Disentangling the cascade of events in the AD is crucial for understanding the disease initiation, progress, and treatment. Our preliminary evidence in this project demonstrates that imposing alteration in the task-based deactivation network does not have any effect on the functional connectivity of the same regions. The current proposal will use asymptomatic stage of Alzheimer’s disease to test whether disruption in the underlying functional connectivity results in any change to the task-based deactivations in the DMN, which is an evidence for hierarchical structure.