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New methodologies for directed functional connectivity applied to brain neuroimaging research
Publication . Rodrigues, João; Andrade, Alexandre da Rocha Freire de, 1971-
In the last decade directed functional connectivity analysis has been increasingly adopted as a method to study the information transfer in the human brain. However, its use with functional neuroimaging data has faced several limitations and controversies, especially when applied to functional magnetic resonance imaging (fMRI) data. This thesis presents a study of directed functional connectivity metrics and their application to datasets from two of the most widely used functional neuroimaging techniques, electroencephalography (EEG) and fMRI. Since a major part of this work focuses on testing and benchmarking connectivity metrics in controlled simulations, an initial study was performed on known generative models, with varying degrees of biophysical fidelity, for the former datasets. Its results suggested that less realistic models are more suitable for large simulations, due to their computational efficiency, or for testing novel metrics, due to their increased control over simulated causal relations. The following study provided a thorough performance assessment of directed functional connectivity metrics in broad experimental simulations with synthetic fMRI data. Our conclusions argued in favor of their applicability in the context of fMRI, provided that a stringent set of experimental specifications is met. The two succeeding studies proposed a novel framework for causal inference, oriented to EEG data, with the use of adaptive data analysis. Their findings suggested that this new framework is able to not only provide improved frequency localization but also to restrict causal analysis to components with physical meaning. The last study provided the opportunity to apply some of the knowledge gathered throughout these studies in the analysis of intracranial EEG data from a patient with infantile spams. From studying the causal relations in the recorded data it was possible to delineate a seizure onset zone that is consistent, and even more specific, with regions determined clinically or by novel localization strategies.
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Fundação para a Ciência e a Tecnologia
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3599-PPCDT
Número da atribuição
PTDC/SAU-ENB/112294/2009