Modulated microwave effects on visual event-related potentials during oddball task

Abstract

The aim of this study was experimental investigation of the effects of low level modulated microwaves on human electroencephalographic (EEG) visual event-related potentials. Thirty healthy volunteers were exposed and sham exposed to electromagnetic field (EMF) (450 MHz, 0.16mW/cm2) modulated at 21Hz modulation frequency during visual oddball tasks. During the task the participants had to distinguish infrequent target stimuli from frequent standard stimuli. The task consisted of visually presented random ball shape stimuli, of which the 25% were target and 75% were standard stimuli. There were two tasks for a subject - EMF exposed task and sham exposed task. One task lasted 10 minutes, during the exposed task the EMF was switched on and off in one-minute intervals, so that the participants performed half of the task in exposed condition (EMF ON) and half of the task without the exposure (EMF OFF). The sham exposed task was identical to exposed task, except the EMF generator was switched off all the time. For analysis of the EEG event-related responses the channel Pz was used. The EEG responses of a task were grouped into four different categories taking into account the EMF exposure condition (ON, OFF) during the response and the response type (standard, target). The responses were averaged by categories. The EMF ON and OFF potentials were compared pair-wise. There were no statistically significant differences in responses in sham exposed tasks, neither in standard nor in target response components. In the exposed task the group mean N100 amplitude (measured from standard response) was -3,41±4,54μV in EMF ON category and -2,50±4,71μV in EMF OFF category, this difference was statistically highly significant (p< 0,00009). Differences in another components' amplitudes, latencies and in RT between EMF ON and OFF conditions were not significant during exposed tasks. It was concluded that modulated microwave effect has stronger impact on sensory components of EEG visual event-related potentials compared to later stages of visual information processing. © 2008 Springer-Verlag.