Dipole theory and electroencephalography.

Abstract

Dipole theory has become a centerpiece of modern discussions regarding the nature of EEG phenomena. Along with dipole theory, the role of volume conduction and, in particular, the inverse problem have gained a powerful position in the modern approach to EEG. An attempt is being made to explore the origins of these concepts. Their advent and rise to a dominant position has been the expression of a new wave of biophysical approaches to EEG. These new trends started in the 1970's and have gradually overshadowed the classical neurophysiological-neurobiological approach. Electrogenesis in cerebral structures and propagation of EEG signals along pathways characterize the "old" EEG theory. It is being pointed out that dipole theory is indeed theory; it is based on spherical models of homogeneous fluid. Attempted adjustments to the brain and its anatomy have been made. Microdipoles at the neuronal level (an essential part of electrogenesis) are plausible; major problems exist as far as macrodipoles are concerned. Differences between the dipole theory in EEG and MEG are discussed. The modern search for the source of a given EEG potential (inverse problem) depends on dipole theory and may be quite misleading. Spread by volume conduction is likely to be vastly exaggerated. A plea is made for mutual understanding and tolerance.