Spectral asymmetry index and Higuchi’s fractal dimension for detecting microwave radiation effect on electroencephalographic signal

This study is aimed to the comparison of the sensitivity of linear spectral asymmetry index (SASI) and nonlinear Higuchi's fractal dimension (HFD) methods for detecting modulated microwave effect on human electroencephalographic (EEG) signal at non-thermal level of exposure. The experiments were carried out on a group of 14 healthy volunteers exposed to 450 MHz microwave radiation modulated at 40 Hz frequency. The applied microwave power was 1 W and the field power density near the head was 0.16 mW/cm2. The EEG signal was recorded from 8 channels: frontal -- FP1, FP2; temporal -- T3, T4; parietal -- P3, P4; and occipital -- O1, O2; with the common recording reference Cz. Microwave exposure increased the group averaged SASI value about 64%. However, the alteration was not statistically significant (p = 0.2). The HFD method detected small (about 1.7%), but statistically significant (p = 0.008) enhancement of its value with microwave exposure.