Department of Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York, NY 10012, USA.
Magn Reson Imaging. 2010 Sep;28(7):995-1003. doi: 10.1016/j.mri.2010.03.007. Epub 2010 Apr 24.
Functional connectivity measures based upon low-frequency blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) signal fluctuations have become a widely used tool for investigating spontaneous brain activity in humans. Still unknown, however, is the precise relationship between neural activity, the hemodynamic response and fluctuations in the MRI signal. Recent work from several groups had shown that correlated low-frequency fluctuations in the BOLD signal can be detected in the anesthetized rat - a first step toward elucidating this relationship. Building on this preliminary work, through this study, we demonstrate that functional connectivity observed in the rat depends strongly on the type of anesthesia used. Power spectra of spontaneous fluctuations and the cross-correlation-based connectivity maps from rats anesthetized with alpha-chloralose, medetomidine or isoflurane are presented using a high-temporal-resolution imaging sequence that ensures minimal contamination from physiological noise. The results show less localized correlation in rats anesthetized with isoflurane as compared with rats anesthetized with alpha-chloralose or medetomidine. These experiments highlight the utility of using different types of anesthesia to explore the fundamental physiological relationships of the BOLD signal and suggest that the mechanisms contributing to functional connectivity involve a complicated relationship between changes in neural activity, neurovascular coupling and vascular reactivity.
基于低频血氧水平依赖功能磁共振成像（BOLD fMRI）信号波动的功能连接测量已成为研究人类自发脑活动的常用工具。然而，神经活动、血流动力学反应和 MRI 信号波动之间的确切关系仍不清楚。最近几个研究小组的工作表明，在麻醉大鼠中可以检测到 BOLD 信号的相关低频波动——这是阐明这种关系的第一步。在此初步工作的基础上，通过这项研究，我们证明了在大鼠中观察到的功能连接强烈依赖于所使用的麻醉类型。使用高时间分辨率成像序列呈现了麻醉大鼠自发波动的功率谱和基于互相关的连接图，该序列可确保最小化生理噪声的污染。结果表明，与使用α-氯醛或甲磺酸二氢麦角碱麻醉的大鼠相比，使用异氟烷麻醉的大鼠的相关性较低。这些实验强调了使用不同类型的麻醉来探索 BOLD 信号的基本生理关系的实用性，并表明导致功能连接的机制涉及神经活动、神经血管耦合和血管反应性变化之间的复杂关系。
