Revealing Small Hidden Changes in Human EEG by Higuchi’s Fractal Dimension

Abstract

The aim of this study was to detect extremely small hidden changes in human EEG by non-linear Higuchi’s fractal dimension (HFD). As a source of small alterations in the EEG the modulated 450 MHz microwave radiation at different modulation frequencies (40 and 70 Hz) was applied at the level of exposure much lower than the health protection limits. The EEG was recorded for a group of 15 subjects during 40 minutes (1 min off, 1 min on). The signals in the P3-P4 EEG channels were selected for comparison. The HFD method revealed significant change at 40 Hz modulation frequency. The trend of changes but no statistically significant effect was detected at 70 Hz modulation frequency. The results confirm that the microwave effect depends on modulation frequency. More specific algorithms are needed for discrimination of the effect in future investigations.