To study the application of Higuchi's fractal dimension as a non-linear measure to evaluate the effect of external periodic stressor (microwave exposure) on electrical oscillations in the brain of 14 participants (21-24 years old, seven males, seven females).
Modulation type: pulsed
Exposure duration: 1 min on - 1 min off, for 10 cycles (20 min)
|Exposure duration||1 min on - 1 min off, for 10 cycles (20 min)|
|Duty cycle||50 %|
|Repetition frequency||40 Hz|
|power density||0.16 mW/cm²||spatial average||estimated||-||+/- 0.02 at the left side of the head|
|power density||0.025 mW/cm²||spatial average||estimated||-||+/- 0.01 at the right side of the head|
|power density||0.08 mW/cm²||spatial average||estimated||-||+/- 0.01 above the head|
|power density||0.8 mW/cm²||spatial average||estimated||-||+/- 0.2 at the left side of the neck and the left shoulder|
|power density||0.03 mW/cm²||spatial average||estimated||-||+/- 0.01 at the right side of the neck and the right shoulder|
|SAR||0.303 W/kg||peak value||calculated||1 g||-|
The data of fractal dimension values averaged over a group detected a small (1-2%) but statistically significant increase with exposure in all EEG channels. The fractal dimension was increased for 12 participants, decreased for one, and was constant for one subject. The fractal dimension showed the most remarkable effect in temporal and parietal regions of the left hemisphere where the microwave field was maximal. Changes of fractal dimension in these regions of the right hemisphere were much higher than expected in accordance with the electromagnetic field distribution.
In conclusion, the data showed that the weak periodic electromagnetic field exposure caused an increase of fractal dimension of the recorded EEG signals. The effect was mild but statistically significant in all EEG channels.