Dynamic coupling between fMRI local connectivity and interictal EEG in focal epilepsy: A wavelet analysis approach.
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. Hum Brain Mapp 38:5356-5374, 2017. © 2017 Wiley Periodicals, Inc.
['Omidvarnia|Amir|A|0000-0002-4744-8721', 'Pedersen|Mangor|M|', 'Vaughan|David N|DN|', 'Walz|Jennifer M|JM|', 'Abbott|David F|DF|0000-0002-7259-8238', 'Zalesky|Andrew|A|', 'Jackson|Graeme D|GD|']
D000328:Adult D019540:Area Under Curve D001921:Brain D001931:Brain Mapping D002560:Cerebrovascular Circulation D015331:Cohort Studies D004569:Electroencephalography D004828:Epilepsies, Partial D005260:Female D006801:Humans D016014:Linear Models D008279:Magnetic Resonance Imaging D008297:Male D064847:Multimodal Imaging D009434:Neural Pathways D000075082:Proof of Concept Study D012372:ROC Curve D012146:Rest D012890:Sleep D013997:Time Factors D058067:Wavelet Analysis
focal epilepsy wavelet coherence DRePS functional connectivity simultaneous EEG-fMRI