Brain Topography

, Volume 32, Issue 2, pp 193–214 | Cite as

Multi-Scale Neural Sources of EEG: Genuine, Equivalent, and Representative. A Tutorial Review

  • Paul L. NunezEmail author
  • Michael D. Nunez
  • Ramesh Srinivasan


A biophysical framework needed to interpret electrophysiological data recorded at multiple spatial scales of brain tissue is developed. Micro current sources at membrane surfaces produce local field potentials, electrocorticography, and electroencephalography (EEG). We categorize multi-scale sources as genuine, equivalent, or representative. Genuine sources occur at the micro scale of cell surfaces. Equivalent sources provide identical experimental outcomes over a range of scales and applications. In contrast, each representative source distribution is just one of many possible source distributions that yield similar experimental outcomes. Macro sources (“dipoles”) may be defined at the macrocolumn (mm) scale and depend on several features of the micro sources—magnitudes, micro synchrony within columns, and distribution through the cortical depths. These micro source properties are determined by brain dynamics and the columnar structure of cortical tissue. The number of representative sources underlying EEG data depends on the spatial scale of neural tissue under study. EEG inverse solutions (e.g. dipole localization) and high resolution estimates (e.g. Laplacian, dura imaging) have both strengths and limitations that depend on experimental conditions. The proposed theoretical framework informs studies of EEG source localization, source characterization, and low pass filtering. It also facilitates interpretations of brain dynamics and cognition, including measures of synchrony, functional connections between cortical locations, and other aspects of brain complexity.


EEG Sources Synchronization Dipole localization Laplacian Spatial scale 



The authors would like to thank members of the IFCN Workshop, and especially its leader, Claudio Babiloni for extended and useful discussions of EEG issues. Comments by the anonymous reviewers and Ed Kelly were also very helpful. This research was supported by National Institutes of Health of the United States Grant 2R01MH68004.

Compliance with Ethical Standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Authors and Affiliations

  1. 1.Cognitive Dissonance LLCEncinitasUSA
  2. 2.Department of Cognitive ScienceUniversity of California at IrvineIrvineUSA
  3. 3.Department of Biomedical EngineeringUniversity of California at IrvineIrvineUSA

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