15/03/2013
Stimulation of the Brain with Radiofrequency Electromagnetic Field Pulses Affects Sleep-Dependent Performance Improvement
Caroline Lustenberger, Manuel Murbach, Roland Dürr, Marc R. Schmid, Niels Kuster, Peter Achermann, and Reto Huber, Brain Stimulation, Volume 6, Issue 5, pp. 805-811, September 2013, online February 26, 2013
This study explores possible mechanisms of how radiofrequency electromagnetic fields (RF EMF) affect cortical activity during sleep and impact sleep-dependent performance changes. Sixteen male subjects were trained in a motor task, to be used to assess changes in overnight performance improvement, and then were exposed overnight to pulsed RF EMF. Each 500 ms RF EMF burst was comprised of 7 × 7.1 ms pulses, each with a peak spatial specific absorption rate averaged over 10 g (psSAR10g) of 10 W/kg, at a burst repetition rate of 0.25 – 0.8 Hz, resulting in an average whole-night psSAR10g of 0.15 W/kg. Electroencephalograms (EEG) were recorded in parallel during the entire sleep period. The slow-wave activity (SWA, 0.75 – 4.5 Hz) increased towards the end of the sleep period and also after the RF EMF bursts in event-related EEG spectral power and phase changes. Sleep-dependent performance improvement after overnight RF EMF exposure was significantly reduced (–20%, P = 0.03) compared to the sham overnight treatment. The changes in the time course of the SWA during overnight exposure may reflect an interaction of RF EMF with the renormalization of cortical excitability during sleep, and we propose two potential interaction mechanisms: (1) oscillatory brain activity caused by sensory perception of RF EMF, or (2) non-synaptic or ephaptic coupling of cortical neurons. Overnight exposure to pulsed RF EMF appears to negatively impact sleep-dependent performance improvement.
The scientific and technical impact of this study can be summarized as:
- We introduce a novel exposure system for application of RF EMF with a circularly polarized field and appropriate RF filtering of the EEG recoding
- Our findings provide further evidence of the influence of RF EMF on brain physiology
- Based on these findings, we suggest two potential mechanisms for the interactions of RF EMF with the brain