Brain Topography

, Volume 13, Issue 2, pp 79–96 | Cite as

On the Relationship of Synaptic Activity to Macroscopic Measurements: Does Co-Registration of EEG with fMRI Make Sense?

  • Paul L. Nunez
  • Richard B. Silberstein


A two-scale theoretical description outlines relationships between brain current sources and the resulting extracranial electric field, recorded as EEG. Finding unknown sources of EEG, the so-calledg “inverse problem”, is discussed in general terms, with emphasis on the fundamental non-uniqueness of inverse solutions. Hemodynamic signatures, measured with fMRI, are expressed as voxel integrals to facilitate comparisons with EEG. Two generally distinct cell groups (1 and 2), generating EEG and fMRI signals respectively, are embedded within the much broader class of synaptic action fields. Cell groups 1 and 2 may or may not overlap in specific experiments. Implications of this incomplete overlap for co-registration studies are considered. Each experimental measure of brain function is generally sensitive to a different kind of source activity and to different spatial and temporal scales. Failure to appreciate such distinctions can exacerbate conflicting views of brain function that emphasize either global integration or functional localization.

EEG ERP fMRI PET Co-registration Generators Current sources Dipole localization 


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Copyright information

© Human Sciences Press, Inc. 2000

Authors and Affiliations

  • Paul L. Nunez
    • 1
    • 2
  • Richard B. Silberstein
    • 1
    • 3
    • 2
  1. 1.The Brain Sciences Institute,Melbourne,Australia
  2. 2.Brain Physics Group, Dept. of Biomedical Engineering,Tulane University,New Orleans,USA
  3. 3.Dept. of Biophysical Sciences and Electrical Engineering,Swinburne University of Technology,Melbourne,Australia

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