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fMRI相关结构的马尔可夫模型:大脑功能连接是小世界还是可分解成网络?

Markov models for fMRI correlation structure: is brain functional connectivity small world, or decomposable into networks?

Gaël Varoquaux, Alexandre Gramfort, Jean Baptiste Poline, Bertrand Thirion

摘要:

通过功能性磁共振成像(fMRI)观察到的信号的相关性,预计将揭示通过血液动力学反应在潜在的神经群体的相互作用。特别是,他们强调了与不同认知功能相关的大脑网络相对应的相互关联区域的分布式集合。然而,神经连接的图论研究给出了一个不同的图景:一个具有小世界特性的高度集成系统:局部聚类,但整个结构中的路径较短。我们研究的功能磁共振成像信号的条件独立性,即其马尔可夫结构,找到现实的假设所需的解释所观察到的功能连接的连接结构。特别是,我们寻求分解的马尔可夫结构到隔离的功能网络使用可分解的图形:一组强连接和部分重叠的集团。我们引入了一种新的方法来有效地提取这样的团在一个大的,强连通图。我们通过测试他们在新数据上学习的模型的拟合优度来比较从功能连接性学习不同图结构的方法。我们发现,将结构概括为强连接网络只能很好地描述非常大的重叠网络。这些结果表明,马尔可夫模型是从fMRI信号中识别大脑连接结构的好工具,但为此目的,它们必须反映底层神经系统的小世界特性。

英文摘要:

Correlations in the signal observed via functional Magnetic Resonance Imaging (fMRI), are expected to reveal the interactions in the underlying neural populations through hemodynamic response. In particular, they highlight distributed set of mutually correlated regions that correspond to brain networks related to different cognitive functions. Yet graph-theoretical studies of neural connections give a different picture: that of a highly integrated system with small-world properties: local clustering but with short pathways across the complete structure. We examine the conditional independence properties of the fMRI signal, i.e. its Markov structure, to find realistic assumptions on the connectivity structure that are required to explain the observed functional connectivity. In particular we seek a decomposition of the Markov structure into segregated functional networks using decomposable graphs: a set of strongly-connected and partially overlapping cliques. We introduce a new method to efficiently extract such cliques on a large, strongly-connected graph. We compare methods learning different graph structures from functional connectivity by testing the goodness of fit of the model they learn on new data. We find that summarizing the structure as strongly-connected networks can give a good description only for very large and overlapping networks. These results highlight that Markov models are good tools to identify the structure of brain connectivity from fMRI signals, but for this purpose they must reflect the small-world properties of the underlying neural systems.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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