Chapter

An Overview of Electromagnetic Fields

Paul L. Nunez and Ramesh Srinivasan

in Electric Fields of the Brain

Second edition

Published in print January 2006 | ISBN: 9780195050387
Published online May 2009 | e-ISBN: 9780199865673 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780195050387.003.0003
 An Overview of Electromagnetic Fields

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This chapter presents the fundamentals of electric currents and fields using very minimal mathematics. The emphasis here differs substantially from that of typical engineering or physics texts for several reasons: EEG is based on ion currents that spread non-uniformly in three dimensions in the head volume conductor, as opposed to one dimensional current in electric circuit wires. The so-called “generators” of EEG are best modeled as current sources in the cerebral cortex; these sources form dipole layers (or sheets) that spread in and out of the cortical folds. Emphasis is placed on the low frequency (quasi-static) fields of EEG, in which electric and magnetic fields are essentially uncoupled. In addition, several genuine electromagnetic phenomena are discussed as possible analogs of EEG dynamic behaviors even though the underlying causes differ. These metaphors include propagation along transmission lines like co-axial TV cables, Schumann resonances in the atmosphere, and food heating mechanisms in microwave ovens.

Keywords: volume conduction; quasi-static fields; ion currents; Schumann resonances; Ohm's law; dielectrics; conductors

Chapter.  20263 words.  Illustrated.

Subjects: Neuroscience

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