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Published November 15, 2014 | Published
Journal Article Open

Effects of millimeter wave irradiation and equivalent thermal heating on the activity of individual neurons in the leech ganglion


Many of today's radiofrequency-emitting devices in telecommunication, telemedicine, transportation safety, and security/military applications use the millimeter-wave (MMW) band (30-300 GHz). To evaluate the biological safety and possible applications of this radiofrequency band for neuroscience and neurology, we have investigated the physiological effects of low-intensity 60 GHz electromagnetic irradiation on individual neurons in the leech midbody ganglia. We applied incident power densities of 1, 2, and 4 mW/cm^2 to the whole ganglion for a period of 1 minute, while recording the action potential with a standard sharp-electrode electrophysiology setup. For comparison, the recognized U.S. safe exposure limit is 1 mW/cm^2 for 6 minutes. During the exposure to MMWs and gradual bath heating at a rate of 0.04 ºC/sec (2.4 ºC/min), the ganglionic neurons exhibited similar dose-dependent hyperpolarization of the plasma membrane and decrease in the action potential amplitude. However, narrowing of the action potential half-width during MMW irradiation at 4 mW/cm^2 was 5 times more pronounced, as compared to equivalent bath heating of 0.6 ºC. Even more dramatic difference in the effects of MMW irradiation and bath heating was on the firing rate, which was suppressed at all applied MMW power densities and was increased in a dose-dependent manner during gradual bath heating. The mechanism of enhanced narrowing of action potentials and suppressed firing by MMW irradiation, as compared to gradual bath heating, is hypothesized to involve specific coupling of MMW energy with the neuronal plasma membrane.

Additional Information

© 2014, Journal of Neurophysiology. Licensed under Creative Commons Attribution CC-BY 3.0. Published 13 August 2014. Sergii Romanenko was funded through a Boswell Postdoctoral Fellowship from Caltech/HMRI and is presently a postdoctoral fellow at LABEX Sigma-Lim – XLIM, Faculté des Sciences et Techniques, Limoges, Cedex, France. Daniel A. Wagenaar was funded through a Career Award at the Scientific Interface from the Burroughs Wellcome Fund and is presently an Assistant Professor at the Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA. Disclosures. The authors declare no competing financial interests.

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