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Title: Dynamic coupling between fMRI local connectivity and interictal EEG in focal epilepsy: a wavelet analysis approach
Austin Authors: Omidvarnia, Amir;Pedersen, Mangor;Vaughan, David N;Walz, Jennifer M;Abbott, David F ;Zalesky, Andrew;Jackson, Graeme D 
Affiliation: The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Heidelberg, Victoria, Australia
Department of Neurology, Austin Health, Heidelberg, Victoria, Australia
Department of Psychiatry, Melbourne Neuropsychiatry Centre, The University of Melbourne and Melbourne Health, Carlton, Victoria, Australia
Melbourne School of Engineering, The University of Melbourne, Parkville, Victoria, Australia
Issue Date: Nov-2017 2017-07-24
Publication information: Human Brain Mapping 2017; 38(11): 5356-5374
Abstract: Simultaneous scalp EEG-fMRI recording is a noninvasive neuroimaging technique for combining electrophysiological and hemodynamic aspects of brain function. Despite the time-varying nature of both measurements, their relationship is usually considered as time-invariant. The aim of this study was to detect direct associations between scalp-recorded EEG and regional changes of hemodynamic brain connectivity in focal epilepsy through a time-frequency paradigm. To do so, we developed a voxel-wise framework that analyses wavelet coherence between dynamic regional phase synchrony (DRePS, calculated from fMRI) and band amplitude fluctuation (BAF) of a target EEG electrode with dominant interictal epileptiform discharges (IEDs). As a proof of concept, we applied this framework to seven patients with focal epilepsy. The analysis produced patient-specific spatial maps of DRePS-BAF coupling, which highlight regions with a strong link between EEG power and local fMRI connectivity. Although we observed DRePS-BAF coupling proximate to the suspected seizure onset zone in some patients, our results suggest that DRePS-BAF is more likely to identify wider 'epileptic networks'. We also compared DRePS-BAF with standard EEG-fMRI analysis based on general linear modelling (GLM). There was, in general, little overlap between the DRePS-BAF maps and GLM maps. However, in some subjects the spatial clusters revealed by these two analyses appeared to be adjacent, particularly in medial posterior cortices. Our findings suggest that (1) there is a strong time-varying relationship between local fMRI connectivity and interictal EEG power in focal epilepsy, and (2) that DRePS-BAF reflect different aspects of epileptic network activity than standard EEG-fMRI analysis. These two techniques, therefore, appear to be complementary.
DOI: 10.1002/hbm.23723
ORCID: 0000-0002-7259-8238
PubMed URL:
Type: Journal Article
Subjects: DRePS
Focal epilepsy
Functional connectivity
Simultaneous EEG-fMRI
Wavelet coherence
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