A default mode of brain function
A default mode of brain function
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DOI：
10.1073/pnas.98.2.676
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发表时间：
2001-01-16
影响因子：
11.1
通讯作者：
Shulman, GL
中科院分区：
文献类型：
--
作者：
Raichle, ME;MacLeod, AM;Shulman, GL
基线或控制状态是理解大多数复杂系统的基础。在人脑中定义基线状态，可以说是我们最复杂的系统，这带来了一个特别的挑战，许多人怀疑，如果不加限制，它的活动将发生不可预测的变化。尽管有这一预测，我们还是根据脑氧提取分数(OEF)确定了正常成人大脑的基线状态，OEF被定义为大脑使用的氧气与流动的血液输送的氧气的比率，在清醒但休息状态(例如，闭着眼睛静静地躺着)中非常均匀。OEF的局部偏差代表了在人类各种行为过程中，通过功能磁共振获得的神经元活动变化信号的生理基础。我们使用来自正电子发射断层扫描的定量代谢和循环测量来获得整个大脑的局部OEF。由于它们的缺席，激活的区域非常明显。所有与平均半球OEF的显著偏差都是增加的，意味着失活，并且几乎完全存在于视觉系统中。以这种方式定义一个区域的基线状态意味着在通过正电子发射断层扫描和功能MRI监测的各种目标导向行为期间，一组区域持续表现出从该基线开始下降的情况。这些下降表明，大脑功能存在一种有组织的、基线的默认模式，在特定的目标导向行为期间暂停。
A baseline or control state is fundamental to the understanding of most complex systems. Defining a baseline state in the human brain, arguably our most complex system, poses a particular challenge, Many suspect that left unconstrained, its activity will vary unpredictably. Despite this prediction we identify a baseline state of the normal adult human brain in terms of the brain oxygen extraction fraction or OEF, The OEF is defined as the ratio of oxygen used by the brain to oxygen delivered by flowing blood and is remarkably uniform in the awake but resting state (e.g., lying quietly with eyes closed). Local deviations in the OEF represent the physiological basis of signals of changes in neuronal activity obtained with functional MRI during a wide variety of human behaviors. We used quantitative metabolic and circulatory measurements from positron-emission tomography to obtain the OEF regionally throughout the brain. Areas of activation were conspicuous by their absence. All significant deviations from the mean hemisphere OEF were increases, signifying deactivations, and resided almost exclusively in the visual system. Defining the baseline state of an area in this manner attaches meaning to a group of areas that consistently exhibit decreases from this baseline, during a wide variety of goal-directed behaviors monitored with positron-emission tomography and functional MRI. These decreases suggest the existence of an organized, baseline default mode of brain function that is suspended during specific goal-directed behaviors.