Functional Perspectives of Endogenous Electric Fields in Humans and Rodents: A Viewpoint on Ephaptic Physiology

Abstract

The present chapter summarizes the functional perspectives of endogenous static and extremely low-frequency electric fields generated in the body of humans and rodents and discusses the possibility of ephaptic interaction. The electric field recorded on the head surface (electroencephalogram) exhibits μV-range amplitude, which is not significantly affected by the brain size. The surface potential is small, but the electric field inside the brain is regionally localized and exhibits an intensity of around 1 V/m. Electric fields with a similar intensity are present in the muscle and skin. These observations suggest that the endogenous electric field shows complex patterns of distribution inside the body. Furthermore, endogenous electric field profiles are influenced by externally applied electric field. Event-related field potentials in the human and rat brain are altered by concomitant static electric field treatment, and externally applied extremely low-frequency electric field induces an increase in electroencephalogram power. These findings would support the presence of ephaptic interaction, which may be related to the modulation of physiological function. Although further research is necessary, an endogenous electric field can serve as a form of interactive information to integrate physiological activities.