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Source separation and higher-order causal analysis of MEG and EEG
Proceedings of the 26th Conference on Uncertainty in Artificial Intelligence, PMLR R8:734-741, 2010.
Abstract
Separation of the sources and analysis of their connectivity have been an important topic in EEG/MEG analysis. To solve this problem in an automatic manner, we propose a two- layer model, in which the sources are con- ditionally uncorrelated from each other, but not independent; the dependence is caused by the causality in their time-varying vari- ances (envelopes). The model is identified in two steps. We first propose a new source separation technique which takes into ac- count the autocorrelations (which may be time-varying) and time-varying variances of the sources. The causality in the envelopes is then discovered by exploiting a special kind of multivariate GARCH (generalized au- toregressive conditional heteroscedasticity) model. The resulting causal diagram gives the effective connectivity between the sep- arated sources; in our experimental results on MEG data, sources with similar functions are grouped together, with negative influ- ences between groups, and the groups are connected via some interesting sources.