University of Zürich

Institute of Pharmacology and Toxicology

Section of Psychopharmacology and Sleep Research

 

 

 

 

Pulsed high-frequency electromagnetic fields affect brain physiology

 

 

Comments

  • Exposure to EMF as defined by the specific absorption rate (SAR) was in the present studies in the range of the exposure during the use of mobile phones.
      
  • The prominent enhancement of spindle frequency activities (15%) was in its extent comparable to the effects induced by zolpidem  [8] and melatonin  [12]. However, the overall pattern of spectral changes differed.
     
  • The absence of hemispheric asymmetry despite unihemispheric EMF exposure (study 2) may suggest a high susceptibility of subcortical structures such as the thalamus.
           
  • It is unlikely that the changes in the sleep EEG were due to thermal effects on the brain:

    1) Considering blood flow and conduction, the rise in brain temperature does not exceed 0.01-0.1 °C     [30].

    2) The time-averaged EMF exposure did not differ between the pulse-modulated and continuous-wave conditions but only the pulse-modulated exposure resulted in an increase of EEG power in the spindle frequency range. The extremely low frequency (ELF) modulation components resulting from the GSM signal shape were at 2, 8, 217, 1736 Hz and higher harmonics. Therefore, either a single frequency component or a mixture of components could be responsible for the observed effects.
     
  • It is shown for the first time that pulse modulation of the EMF is necessary to induce changes in the waking and sleep EEG.
  • The processes underlying the present effects remain obscure. 

    The decline of the EEG changes in the course of sleep during exposure (study 1) pointed to an adaptation mechanism. The absence of a modulation of the EEG by the EMF on-off cycle suggests that field exposure triggered a chain of events rather than exerted a direct and immediate effect on sleep control. 

    The effects outlasted exposure by 20-50 min when EMF is applied during waking prior to daytime sleep (study 2). 

    Surprisingly, after exposure prior to a nocturnal sleep episode, the changes appeared to increase in the course of the night (study 3). Thus, the effects outlasted exposure up to 8 h. EMF exposure that gave rise to the initial post-exposure modification of cortical regional cerebral blood flow and to the increase in pre-sleep alpha activity may have induced long-term effects on spindle generating mechanisms that became more apparent as spindle frequency activity increased in the course of the night. Alternatively, EMF exposure may have affected the phase of the circadian pacemaker, thereby altering the time course of spindle frequency activity.
     
  • In two experiments it has been shown that exposure to EMF during waking affected the EEG during the subsequent sleep episode.
      
  • The present results lend support to previous reports on effects of EMF on physiological and psychological variables. These include sleep [22] and cognitive function [16,17,19,27] as well as blood pressure and heart-rate [7]. 
     
  • The observed reduction of waking after sleep onset (study 1) may be related to the finding of a previous study  reporting a successful treatment of insomnia with EMF exposure (27.12 MHz; low energy emission therapy; LEET) [25].

 

 

  1. [7] Braune S., Wrocklage C., Raczek J., Gailus T., and Lucking C. H. (1998) Resting blood pressure increase during exposure to a radio-frequency electromagnetic field. Lancet 351, 1857-8.
  2. [16] Koivisto M., Krause C. M., Revonsuo A., Laine M., and Hämäläinen H. (2000) The effects of electromagnetic field emitted by GSM phones on working memory. NeuroReport 11, 1641-1643.
  3. [17 ]Koivisto M., Revonsuo A., Krause C. M., Haarala C., Laine M., and Hämäläinen H. (2000) Effects of 902 MHz electromagnetic field emitted by cellular telephones on response times in humans. NeuroReport 11, 413-415.
  4. [ 19 ]Krause C. M., Sillanmäki L., Koivisto M., Häggqvist A., Saarela C., Revonsuo A., Laine M., and Hämäläinen H. (2000) Effects of electromagnetic field emitted by cellular phones on the EEG during a memory task. NeuroReport 11, 761-764.
  5. [20 ]Landolt H. P., Dijk D. J., Gaus S. E., and Borbély A. A. (1995) Caffeine reduces low-frequency delta activity in the human sleep EEG. Neuropsychopharmacol. 12, 229-38.
  6. [22] Mann K. and Röschke J. (1996) Effects of pulsed high-frequency electromagnetic fields on human sleep. Neuropsychobiology 33, 41-7.
  7. [25] Pasche B., Erman M., Hayduk R., Mitler M. M., Reite M., Higgs L., Kuster N., Rossel C., Dafni U., Amato D., Barbault A., and Lebet J. P. (1996) Effects of low energy emission therapy in chronic psychophysiological insomnia. Sleep 19, 327-36.
  8. [27] Preece A. W., Iwi G., Davies-Smith A., Wesnes K., Butler S., Lim E., and Varey A. (1999) Effect of a 915-MHz simulated mobile phone signal on cognitive function in man. Int J Radiat Biol 75, 447-456.
  9.