The experiments were designed with two objectives: 1) to study the reactivity of the "EEG burst suppression pattern" (see below) to the electromagnetic field stimulation and 2) to study the changes in the EEG signal due to continuous high power electromagnetic field exposure.
Eleven pigs were anaesthetised to the level where "burst-suppression pattern" appears in the EEG. At this level of anaesthesia both human subjects and animals show high sensitivity to external stimuli which produce EEG bursts during suppression (the low-amplitude EEG abruptly switches to very high amplitude bursts). This switching can be triggered by very minor stimuli and the phenomenon has been described as "hypersensitivity".
In the first phase of the experiment electromagnetic field stimulation (as external stimulus) was randomly switched on and off and the relation between EEG bursts and electromagnetic field stimulation onsets and endpoints were studied. In the second phase a continuous radiofrequency stimulation at 31 W/kg was applied for 10 minutes.
|Exposure duration||20 -30 min|
The exposure to 890 MHz electromagnetic field stimulation at 31 W/kg increased the subcutaneous temperature of the pigs by about 1.6°C and the heart rate by 14.2 beats per minute in a group of six anaesthetised pigs. No significant changes were observed in the EEG activity of the animals although several EEG signal analysis methods were applied. In a group of ten pigs, anaesthetized to the level where the EEG burst suppression pattern occurs, no correlation was found between switching on or off the electromagnetic field stimulation and triggering of the bursts.
In none of the pigs there was any sign of the "hypersensitive nonlinear burst suppression control system". Thus, the data indicate that the radiofrequency exposure does not produce sensory stimulation of somatosensory, auditory or visual system or directly affect the brain so as to produce EEG bursts during suppression. The slow rise in temperature at very high radiofrequency intensity suggests that there is an effect also in brain tissue, but this is not appropriate, intensive or abrupt enough to trigger the burst control system.