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Scientific article
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Simultaneous Intracranial EEG-fMRI Shows Inter-Modality Correlation in Time-Resolved Connectivity Within Normal Areas but Not Within Epileptic Regions

Published inBrain topography, vol. 30, no. 5, p. 639-655
Publication date2017
Abstract

For the first time in research in humans, we used simultaneous icEEG-fMRI to examine the link between connectivity in haemodynamic signals during the resting-state (rs) and connectivity derived from electrophysiological activity in terms of the inter-modal connectivity correlation (IMCC). We quantified IMCC in nine patients with drug-resistant epilepsy (i) within brain networks in 'healthy' non-involved cortical zones (NIZ) and (ii) within brain networks involved in generating seizures and interictal spikes (IZ1) or solely spikes (IZ2). Functional connectivity (h 2 ) estimates for 10 min of resting-state data were obtained between each pair of electrodes within each clinical zone for both icEEG and fMRI. A sliding window approach allowed us to quantify the variability over time of h 2 (vh 2) as an indicator of connectivity dynamics. We observe significant positive IMCC for h 2 and vh 2, for multiple bands in the NIZ only, with the strongest effect in the lower icEEG frequencies. Similarly, intra-modal h 2 and vh 2 were found to be differently modified as a function of different epileptic processes: compared to NIZ, [Formula: see text] was higher in IZ1, but lower in IZ2, while [Formula: see text] showed the inverse pattern. This corroborates previous observations of inter-modal connectivity discrepancies in pathological cortices, while providing the first direct invasive and simultaneous comparison in humans. We also studied time-resolved FC variability multimodally for the first time, finding that IZ1 shows both elevated internal [Formula: see text] and less rich dynamical variability, suggesting that its chronic role in epileptogenesis may be linked to greater homogeneity in self-sustaining pathological oscillatory states.

Keywords
  • Adult
  • Brain/diagnostic imaging/physiopathology
  • Brain Mapping
  • Electroencephalography/methods
  • Epilepsy/diagnostic imaging/physiopathology
  • Female
  • Humans
  • Magnetic Resonance Imaging/methods
  • Male
  • Multimodal Imaging
  • Nerve Net/diagnostic imaging/physiopathology
  • Seizures/diagnostic imaging/physiopathology
  • Young Adult
Funding
  • Swiss National Science Foundation - 141165
  • Swiss National Science Foundation - 140332
Citation (ISO format)
RIDLEY, Ben et al. Simultaneous Intracranial EEG-fMRI Shows Inter-Modality Correlation in Time-Resolved Connectivity Within Normal Areas but Not Within Epileptic Regions. In: Brain topography, 2017, vol. 30, n° 5, p. 639–655. doi: 10.1007/s10548-017-0551-5
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Article (Published version)
accessLevelRestricted
Identifiers
ISSN of the journal0896-0267
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