Coupling of cerebral blood flow and oxygen consumption during physiological activation and deactivation measured with fMRI
Coupling of cerebral blood flow and oxygen consumption during physiological activation and deactivation measured with fMRI
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DOI：
10.1016/j.neuroimage.2004.05.013
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发表时间：
2004-09-01
期刊：
影响因子：
5.7
通讯作者：
Buxton, RB
中科院分区：
文献类型：
--
作者：
Uludag, K;Dubowitz, DJ;Buxton, RB
通过比较基线改变后对视觉刺激的反应，研究血氧水平依赖(BOLD)信号的生理基础及其对基线脑血流量(CBF)的依赖性。对8名受试者分别用3T和4T磁共振扫描仪进行成像，同时测量BOLD信号和脑血流。在区块设计实验中，受试者观看了一个闪烁的放射状棋盘，在关闭期间交替睁眼或闭眼。与在黑暗的房间中睁开眼睛的基线状态相比，当闭上眼睛时，观察到枕叶皮质的显著失活(平均变化：2.9+/-0.3%BOLD，22+/-2.1%CBF)。刺激时的绝对反应(平均变化：4.4+/-0.4%BOLD，36.3+/-3.1%CBF)与之前的静息状态无关。我们估计CBF的分数变化大约是氧代谢率(CMRO2)分数变化的2.2+/-0.15倍。在激活和失活期间，CBF和CMRO2的变化始终是线性耦合的，与睁开眼睛的基线相比，CBF的变化大约在60%到150%之间。相对于假设的40%的基线氧提取分数(OEF)，估计的OEF在激活期间下降到33+/-1.4%，在闭眼休息时增加到46+/-1.2%。总而言之，我们发现，简单地闭上眼睛会在视觉皮质产生大量的生理失活，并为研究fMRI的基线效应提供了一个可靠的范例。此外，我们提出了一个神经血管偶联的前馈模型，该模型解释了基线变化后OEF的变化，包括当前的生理扰动以及先前报道的药物诱导的变化。(C)2004 Elsevier Inc.保留所有权利。
The physiological basis of the blood oxygenation level dependent (BOLD) signal and its dependence on baseline cerebral blood flow (CBF) were investigated by comparing responses to a visual stimulus after physiological changes of the baseline. Eight human subjects were imaged with 3 and 4 T MRI scanners, and both BOLD signal and CBF were simultaneously measured. Subjects viewed a flickering radial checkerboard in a block design experiment, alternating between eyes open or closed during the off periods. Compared to a baseline state with eyes open in a darkened room, substantial deactivation (average change: 2.9 +/- 0.3% BOLD, 22 +/- 2.1 % CBF) in the occipital cortex was observed when the eyes were closed. The absolute response during stimulation (average change: 4.4 +/- 0.4% BOLD, 36.3 +/- 3.1% CBF) was independent of the preceding resting condition. We estimated the fractional change in CBF to be approximately 2.2 +/- 0.15 times greater than the fractional change in metabolic rate of oxygen (CMRO2). The changes in CBF and CMRO2 were consistently linearly coupled during activation and deactivation with CBF changes being between approximately 60% and 150% compared to baseline with eyes open. Relative to an assumed baseline oxygen extraction fraction (OEF) of 40%, the estimated OEF decreased to 33 +/- 1.4% during activation and increased to 46 +/- 1.2% during rest with eyes closed. In conclusion, we found that simply closing the eyes creates a large physiological deactivation in the visual cortex, and provides a robust paradigm for studying baseline effects in fMRI. In addition, we propose a feedforward model for neurovascular coupling which accounts for the changes in OEF seen following baseline changes, including both the current physiological perturbations as well as previously reported pharmacologically induced changes. (C) 2004 Elsevier Inc. All rights reserved.