Chicharro Daniel, Panzeri Stefano
Neural Computation Laboratory, Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia Rovereto, Italy.
Neural Computation Laboratory, Center for Neuroscience and Cognitive Systems@UniTn, Istituto Italiano di Tecnologia Rovereto, Italy ; Institute of Neuroscience and Psychology, University of Glasgow Glasgow, UK.
Front Neuroinform. 2014 Jul 2;8:64. doi: 10.3389/fninf.2014.00064. eCollection 2014.
In recent years, powerful general algorithms of causal inference have been developed. In particular, in the framework of Pearl's causality, algorithms of inductive causation (IC and IC(*)) provide a procedure to determine which causal connections among nodes in a network can be inferred from empirical observations even in the presence of latent variables, indicating the limits of what can be learned without active manipulation of the system. These algorithms can in principle become important complements to established techniques such as Granger causality and Dynamic Causal Modeling (DCM) to analyze causal influences (effective connectivity) among brain regions. However, their application to dynamic processes has not been yet examined. Here we study how to apply these algorithms to time-varying signals such as electrophysiological or neuroimaging signals. We propose a new algorithm which combines the basic principles of the previous algorithms with Granger causality to obtain a representation of the causal relations suited to dynamic processes. Furthermore, we use graphical criteria to predict dynamic statistical dependencies between the signals from the causal structure. We show how some problems for causal inference from neural signals (e.g., measurement noise, hemodynamic responses, and time aggregation) can be understood in a general graphical approach. Focusing on the effect of spatial aggregation, we show that when causal inference is performed at a coarser scale than the one at which the neural sources interact, results strongly depend on the degree of integration of the neural sources aggregated in the signals, and thus characterize more the intra-areal properties than the interactions among regions. We finally discuss how the explicit consideration of latent processes contributes to understand Granger causality and DCM as well as to distinguish functional and effective connectivity.
近年来,已经开发出了强大的因果推断通用算法。特别是在珀尔因果关系框架下,归纳因果算法(IC和IC(*))提供了一种程序,用于确定即使在存在潜在变量的情况下,网络中节点之间的哪些因果联系可以从经验观察中推断出来,这表明了在不对系统进行主动操纵的情况下能够学到的知识的局限性。这些算法原则上可以成为格兰杰因果关系和动态因果建模(DCM)等既定技术的重要补充,以分析脑区之间的因果影响(有效连接性)。然而,它们在动态过程中的应用尚未得到检验。在这里,我们研究如何将这些算法应用于时变信号,如电生理或神经成像信号。我们提出了一种新算法,该算法将先前算法的基本原理与格兰杰因果关系相结合,以获得适合动态过程的因果关系表示。此外,我们使用图形标准从因果结构预测信号之间的动态统计依赖性。我们展示了如何用一种通用的图形方法来理解神经信号因果推断中的一些问题(例如测量噪声、血液动力学反应和时间聚合)。聚焦于空间聚合的影响,我们表明,当在比神经源相互作用的尺度更粗的尺度上进行因果推断时,结果强烈依赖于信号中聚合的神经源的整合程度,因此更多地表征了区域内属性而非区域间的相互作用。我们最后讨论了对潜在过程的明确考虑如何有助于理解格兰杰因果关系和DCM,以及区分功能连接性和有效连接性。