Noninvasive Electromagnetic Source Imaging and Granger Causality Analysis: An Electrophysiological Connectome (eConnectome) Approach

Abbas Sohrabpour, Shuai Ye, Gregory A. Worrell, Wenbo Zhang, Bin He

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Objective: Combined source-imaging techniques and directional connectivity analysis can provide useful information about the underlying brain networks in a noninvasive fashion. Source-imaging techniques have been used successfully to either determine the source of activity or to extract source time-courses for Granger causality analysis, previously. In this work, we utilize source-imaging algorithms to both find the network nodes [regions of interest (ROI)] and then extract the activation time series for further Granger causality analysis. The aim of this work is to find network nodes objectively from noninvasive electromagnetic signals, extract activation time-courses, and apply Granger analysis on the extracted series to study brain networks under realistic conditions. Methods : Source-imaging methods are used to identify network nodes and extract time-courses and then Granger causality analysis is applied to delineate the directional functional connectivity of underlying brain networks. Computer simulations studies where the underlying network (nodes and connectivity pattern) is known were performed; additionally, this approach has been evaluated in partial epilepsy patients to study epilepsy networks from interictal and ictal signals recorded by EEG and/or Magnetoencephalography (MEG). Results: Localization errors of network nodes are less than 5 mm and normalized connectivity errors of ∼20% in estimating underlying brain networks in simulation studies. Additionally, two focal epilepsy patients were studied and the identified nodes driving the epileptic network were concordant with clinical findings from intracranial recordings or surgical resection. Conclusion: Our study indicates that combined source-imaging algorithms with Granger causality analysis can identify underlying networks precisely (both in terms of network nodes location and internodal connectivity). Significance: The combined source imaging and Granger analysis technique is an effective tool for studying normal or pathological brain conditions.

Original languageEnglish (US)
Article number7588130
Pages (from-to)2474-2487
Number of pages14
JournalIEEE Transactions on Biomedical Engineering
Issue number12
StatePublished - Dec 2016

Bibliographical note

Publisher Copyright:
© 2016 IEEE.


  • Directed transfer function (DTF)
  • Granger causality analysis
  • dynamic seizure imaging (DSI)
  • electromagnetic source imaging (ESI)
  • high-density electroencephalography (EEG)
  • interictal spikes (IIS)
  • magnetoencephalography (MEG)
  • network


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