Study type: Medical/biological study (experimental study)

Higuchi's fractal dimension for analysis of the effect of external periodic stressor on electrical oscillations in the brain. med./bio.

Published in: Med Biol Eng Comput 2011; 49 (5): 585-591

Aim of study (acc. to author)

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).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 450 MHz
Modulation type: pulsed
Exposure duration: 1 min on - 1 min off, for 10 cycles (20 min)
  • power density: 0.16 mW/cm² spatial average (+/- 0.02 at the left side of the head)
  • power density: 0.025 mW/cm² spatial average (+/- 0.01 at the right side of the head)
  • power density: 0.08 mW/cm² spatial average (+/- 0.01 above the head)
  • power density: 0.8 mW/cm² spatial average (+/- 0.2 at the left side of the neck and the left shoulder)
  • power density: 0.03 mW/cm² spatial average (+/- 0.01 at the right side of the neck and the right shoulder)
  • SAR: 0.303 W/kg peak value (1 g)

Exposure 1

Main characteristics
Frequency 450 MHz
Type
Exposure duration 1 min on - 1 min off, for 10 cycles (20 min)
Modulation
Modulation type pulsed
Duty cycle 50 %
Repetition frequency 40 Hz
Exposure setup
Exposure source
Setup antenna placed at a distance of 10 cm from the skin of the left side of the head
Parameters
Measurand Value Type Method Mass Remarks
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 -

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • before exposure
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

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.

Study character:

Study funded by

Related articles