title: Stimulation of the brain with radiofrequency electromagnetic field pulses affects sleep-dependent performance improvement.
abstract: BACKGROUND
  Sleep-dependent performance improvements seem to be closely related to sleep spindles (12-15 Hz) and sleep slow-wave activity (SWA, 0.75-4.5 Hz). Pulse-modulated radiofrequency electromagnetic fields (RF EMF, carrier frequency 900 MHz) are capable to modulate these electroencephalographic (EEG) characteristics of sleep.
  
  
  OBJECTIVE
  The aim of our study was to explore possible mechanisms how RF EMF affect cortical activity during sleep and to test whether such effects on cortical activity during sleep interact with sleep-dependent performance changes.
  
  
  METHODS
  Sixteen male subjects underwent 2 experimental nights, one of them with all-night 0.25-0.8 Hz pulsed RF EMF exposure. All-night EEG was recorded. To investigate RF EMF induced changes in overnight performance improvement, subjects were trained for both nights on a motor task in the evening and the morning.
  
  
  RESULTS
  We obtained good sleep quality in all subjects under both conditions (mean sleep efficiency > 90%). After pulsed RF EMF we found increased SWA during exposure to pulse-modulated RF EMF compared to sham exposure (P < 0.05) toward the end of the sleep period. Spindle activity was not affected. Moreover, subjects showed an increased RF EMF burst-related response in the SWA range, indicated by an increase in event-related EEG spectral power and phase changes in the SWA range. Notably, during exposure, sleep-dependent performance improvement in the motor sequence task was reduced compared to the sham condition (-20.1%, P = 0.03).
  
  
  CONCLUSIONS
  The changes in the time course of SWA during the exposure night may reflect an interaction of RF EMF with the renormalization of cortical excitability during sleep, with a negative impact on sleep-dependent performance improvement.
authors.affiliation: University Children's Hospital Zurich, Child Development Center, Steinwiesstrasse 75, 8032 Zurich, Switzerland; Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland.
authors.forename: Caroline
authors.initials: C
authors.lastname: Lustenberger
authors.forename: Manuel
authors.initials: M
authors.lastname: Murbach
authors.forename: Roland
authors.initials: R
authors.lastname: Dürr
authors.forename: Marc Ralph
authors.initials: MR
authors.lastname: Schmid
authors.forename: Niels
authors.initials: N
authors.lastname: Kuster
authors.forename: Peter
authors.initials: P
authors.lastname: Achermann
authors.forename: Reto
authors.initials: R
authors.lastname: Huber
mesh_terms: D000293:Adolescent; D001921:Brain / Q000502:physiology / Q000528:radiation effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004569:Electroencephalography; D004574:Electromagnetic Fields / Q000009:adverse effects*; D006801:Humans; D008297:Male; D011597:Psychomotor Performance / Q000528:radiation effects*; D011846:Radio Waves / Q000009:adverse effects*; D012890:Sleep / Q000502:physiology / Q000528:radiation effects*; D055815:Young Adult
keywords: Memory consolidation; Mobile phones; Sleep EEG; Synaptic plasticity