Dodel Silke, Golestani Narly, Pallier Christophe, Elkouby Vincent, Le Bihan Denis, Poline Jean-Baptiste
Service Hospitalier Frédéric Joliot, CEA, IFR49, 91401 Orsay, France.
Philos Trans R Soc Lond B Biol Sci. 2005 May 29;360(1457):921-35. doi: 10.1098/rstb.2005.1653.
This paper introduces a method to study the variation of brain functional connectivity networks with respect to experimental conditions in fMRI data. It is related to the psychophysiological interaction technique introduced by Friston et al. and extends to networks of correlation modulation (CM networks). Extended networks containing several dozens of nodes are determined in which the links correspond to consistent correlation modulation across subjects. In addition, we assess inter-subject variability and determine networks in which the condition-dependent functional interactions can be explained by a subject-dependent variable. We applied the technique to data from a study on syntactical production in bilinguals and analysed functional interactions differentially across tasks (word reading or sentence production) and across languages. We find an extended network of consistent functional interaction modulation across tasks, whereas the network comparing languages shows fewer links. Interestingly, there is evidence for a specific network in which the differences in functional interaction across subjects can be explained by differences in the subjects' syntactical proficiency. Specifically, we find that regions, including ones that have previously been shown to be involved in syntax and in language production, such as the left inferior frontal gyrus, putamen, insula, precentral gyrus, as well as the supplementary motor area, are more functionally linked during sentence production in the second, compared with the first, language in syntactically more proficient bilinguals than in syntactically less proficient ones. Our approach extends conventional activation analyses to the notion of networks, emphasizing functional interactions between regions independently of whether or not they are activated. On the one hand, it gives rise to testable hypotheses and allows an interpretation of the results in terms of the previous literature, and on the other hand, it provides a basis for studying the structure of functional interactions as a whole, and hence represents a further step towards the notion of large-scale networks in functional imaging.
本文介绍了一种研究功能磁共振成像（fMRI）数据中脑功能连接网络随实验条件变化的方法。它与弗里斯顿等人提出的心理生理交互技术相关，并扩展到相关调制网络（CM网络）。确定了包含几十个节点的扩展网络，其中的连接对应于受试者之间一致的相关调制。此外，我们评估了受试者间的变异性，并确定了条件依赖性功能交互可由受试者依赖变量解释的网络。我们将该技术应用于一项关于双语者句法生成的研究数据，并分析了不同任务（单词阅读或句子生成）和不同语言之间的功能交互差异。我们发现了一个跨任务一致功能交互调制的扩展网络，而比较语言的网络显示的连接较少。有趣的是，有证据表明存在一个特定网络，其中受试者间功能交互的差异可由受试者句法熟练度的差异来解释。具体而言，我们发现，包括先前已被证明参与句法和语言生成的区域，如左侧额下回、壳核、脑岛、中央前回以及辅助运动区，在句法更熟练的双语者中，与第一语言相比，第二语言的句子生成过程中这些区域之间的功能连接更强，而在句法不太熟练的双语者中则不然。我们的方法将传统的激活分析扩展到网络概念，强调区域之间的功能交互，而不考虑它们是否被激活。一方面，它产生了可检验的假设，并允许根据先前的文献对结果进行解释，另一方面，它为整体研究功能交互的结构提供了基础，因此代表了功能成像中迈向大规模网络概念的又一步。
