Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN 55455, USA.
Cereb Cortex. 2011 Feb;21(2):374-84. doi: 10.1093/cercor/bhq105. Epub 2010 Jun 7.
Spontaneous hemodynamic signals fluctuate coherently within many resting-brain functional networks not only in awake humans and lightly anesthetized primates but also in animals under deep anesthesia characterized by burst-suppression electroencephalogram (EEG) activity and unconsciousness. To understand the neural origin of spontaneous hemodynamic fluctuations under such a deep anesthesia state, epidural EEG and cerebral blood flow (CBF) were simultaneously recorded from the bilateral somatosensory cortical regions of rats with isoflurane-induced burst-suppression EEG activity. Strong neurovascular coupling was observed between spontaneous EEG "bursts" and CBF "bumps," both of which were also highly synchronized across the 2 hemispheres. Functional magnetic resonance imaging (fMRI) was used to image spontaneous blood oxygen level-dependent (BOLD) signals under the same anesthesia conditions and showed similar BOLD "bumps" and dependence on anesthesia depth as the CBF signals. The spatiotemporal BOLD correlations indicate a strong but less-specific coherent network covering a wide range of cortical regions. The overall findings reveal that the spontaneous CBF/BOLD fluctuations under unconscious burst-suppression anesthesia conditions originate mainly from underlying neural activity. They provide insights into the neurophysiological basis for the use of BOLD- and CBF-based fMRI signals for noninvasively imaging spontaneous and synchronous brain activity under various brain states.
自发性血流动力学信号在许多静息态脑功能网络中不仅在清醒的人类和轻度麻醉的灵长类动物中，而且在以爆发抑制脑电图 (EEG) 活动和无意识为特征的深度麻醉动物中也呈现出相干波动。为了了解在这种深度麻醉状态下自发性血流动力学波动的神经起源，我们从双侧体感皮质区域同时记录了异氟醚诱导的爆发抑制 EEG 活动的大鼠硬膜外 EEG 和脑血流 (CBF)。自发性 EEG“爆发”和 CBF“隆起”之间观察到强烈的神经血管耦合，两者在两个半球之间也高度同步。功能性磁共振成像 (fMRI) 用于在相同麻醉条件下对自发性血氧水平依赖 (BOLD) 信号进行成像，结果显示与 CBF 信号相似的 BOLD“隆起”和对麻醉深度的依赖性。BOLD 相关性的时空分布表明存在一个强烈但不那么特异的相干网络，覆盖了广泛的皮质区域。总体研究结果表明，无意识爆发抑制麻醉条件下的自发性 CBF/BOLD 波动主要源自潜在的神经活动。它们为使用 BOLD 和 CBF 为基础的 fMRI 信号在各种大脑状态下非侵入性地成像自发性和同步脑活动提供了神经生理学基础。
