Auteurs

Lipping, T. Rorarius, M. Jantti, V. Annala, K. Mennander, A. Ferenets, R. Toivonen, T. Toivo, T. Varri, A. and Korpinen, L. Using the nonlinear control of anaesthesia-induced hypersensitivity of EEG at burst suppression level to test the effects of radiofrequency radiation on brain function. Nonlinear Biomed Phys. 2009; 3(1):5.

Introduction
Studies on the effect of radiofrequency fields (RF) exposure on brain functions have yielded conflicting results. There are reports from animal experiments that exposure to modulated RF fields produce changes on electroencephalogram (EEG), but the positive findings have not been followed up. Compared to the waking condition, EEG during anesthesia is less variable, and changes in EEG properties produced by anesthesia itself are well known. It has been previously shown that during burst suppression, i.e. the phase of anesthesia when periods of low-amplitude EEG alternate with high amplitude bursts, the burst can be produced by minor stimuli. This phenomenon has been described as hypersensitivity.

Objectives
The objective was twofold: 1) to study the reactivity of the EEG burst suppression pattern to the stimulation by RF radiation from the GSM mobile phone; 2) to study changes in the EEG signal in response to continuous RF stimulation at high SAR.

Methods
Eleven anesthetized pigs were exposed to pulse modulated signal of a GSM mobile phone at 890 MHz. In the first phase, the electromagnetic field (EMF) stimulation was switched on and off for 1-10 seconds at irregular intervals during 10-20 minutes, first at SAR 7.3 W/kg and then at SAR 31 W/kg (maximum 10 g average). The EEG signal was analyzed visually to study the temporal relation between the EMF stimuli and EEG bursts. In the second phase of the experiment, the EMF source was switched on continuously for 10 minutes at SAR of 31 W/kg. The ECG (to obtain heart rate), EEG, and the subcutaneous temperature were recorded.

Results
No correlation was observed between the timing of the EMF stimuli and the EEG bursts in phase I. No significant changes were recorded in the EEG activity during continuous EMF exposure in phase II. During the 10 minute exposure, the subcutaneous temperature increased by 1.63 degrees and the heart rate increased by 14.15 beats per minute on average. There was no clear correlation between the magnitude of changes in the heart rate and temperature increase.

Interpretation and Conclusion
These results indicate that exposure to RF radiation does not produce sensory stimulation or directly affect the brain so as to produce EEG bursts during suppression. The slow temperature rise at very high SAR level suggests that there may be an effect in brain tissue, but this is not appropriate or sufficient to trigger the burst control system.

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