Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT, USA.
Neuroimage. 2011 Oct 15;58(4):1044-50. doi: 10.1016/j.neuroimage.2011.06.075. Epub 2011 Jul 2.
The analysis of spontaneous fluctuations of functional magnetic resonance imaging (fMRI) signals has recently gained attention as a powerful tool for investigating brain circuits in a non-invasive manner. Correlation-based connectivity analysis investigates the correlations of spontaneous fluctuations of the fMRI signal either between a single seed region of interest (ROI) and the rest of the brain or between multiple ROIs. To do this, a priori knowledge is required for defining the ROI(s) and without such knowledge functional connectivity fMRI cannot be used as an exploratory tool for investigating the functional organization of the brain and its modulation under different conditions. In this work we examine two indices that provide voxel based maps reflecting the intrinsic connectivity contrast (ICC) of individual tissue elements without the need for defining ROIs and hence require no a priori information or assumptions. These voxel based ICC measures can also be used to delineate regions of interest for further functional or network analyses. The indices were applied to the study of sevoflurane anesthesia-induced alterations in intrinsic connectivity. In concordance with previous studies, the results show that sevoflurane affects different brain circuits in a heterogeneous manner. In addition ICC analyses revealed changes in regions not previously identified using conventional ROI connectivity analyses, probably because of an inappropriate choice of the ROI in the earlier studies. This work highlights the importance of such voxel based connectivity methodology.
静息态功能磁共振成像（fMRI）信号的自发性波动分析最近作为一种非侵入性研究脑回路的强大工具受到关注。基于相关的连接分析研究了 fMRI 信号的自发性波动在单个感兴趣区（ROI）与大脑其余部分之间或多个 ROI 之间的相关性。为此，需要先验知识来定义 ROI，如果没有这种知识，功能连接 fMRI 就不能作为探索性工具来研究大脑的功能组织及其在不同条件下的调制。在这项工作中，我们检查了两个指标，这些指标提供了基于体素的映射，反映了单个组织元素的固有连接对比度（ICC），而无需定义 ROI，因此不需要先验信息或假设。这些基于体素的 ICC 测量值也可用于描绘进一步进行功能或网络分析的感兴趣区域。这些指标被应用于研究七氟醚麻醉诱导的固有连接改变。与先前的研究一致，结果表明七氟醚以不均匀的方式影响不同的脑回路。此外，ICC 分析显示，在以前使用常规 ROI 连接分析未识别的区域发生了变化，这可能是由于在早期研究中选择 ROI 不恰当。这项工作强调了这种基于体素的连接方法的重要性。
