Medical/biological study (experimental study)

Effect of 7, 14 and 21 Hz modulated 450 MHz microwave radiation on human electroencephalographic rhythms med./bio.

By: Hinrikus H, Bachmann M, Lass J, Tomson R, Tuulik V

Published in: Int J Radiat Biol 2008; 84 (1): 69-79

Aim of study (acc. to author)

To study the effect of microwaves modulated at different frequencies (7, 14 and 21 Hz) on human electroencephalographic (EEG) rhythms.

Background/further details

13 subject participated.

Endpoint

effects on the neurological system: EEG rhythm

Exposure

- microwaves

Exposure	Parameters
Exposure 1: 450 MHz Modulation type: pulsed Exposure duration: intermittent, 1 min off/1 min on, for 10 min per frequency	power density: 0.16 mW/cm² mean SAR: 0.35 W/kg ([Hinrikus et al., 2004])

General information

Each subject went through two (or four?) EEG recording sessions on different days, double-blind and randomly assigned to real and sham exposure. Both exposure and sham protocols were applied twice to each subject. Microwave exposure was identical to previous studies [Lass et al., 2002 and Hinrikus et al., 2004], but three different modulation frequencies were applied.

Exposure 1

Main characteristics

Frequency	450 MHz
Type	electromagnetic field
Exposure duration	intermittent, 1 min off/1 min on, for 10 min per frequency

Modulation

Modulation type	pulsed
Duty cycle	50 %
Additional info	pulse rates of 7, 14, or 21 Hz

Exposure setup

Exposure source	quarter-wave antenna (13 cm)
Distance between exposed object and exposure source	10 cm
Chamber	During the EEG recording session, lasting 40 min, subjects were lying in a relaxed position, with eyes closed and ears blocked, in a dark room. The experimenter was also in the room.
Setup	The antenna was located 10 cm from the skin on the left side of the head.
Sham exposure	A sham exposure was conducted.
Additional info	10 minutes of reference recordings were followed by three times 10 min of exposure at a constant modulation frequency of 7, 14, or 21 Hz. The succession of the modulation frequencies was randomly assigned by a computer program.

Parameters

Measurand	Value	Type	Method	Mass	Remarks
power density	0.16 mW/cm²	mean	estimated	-	-
SAR	0.35 W/kg	-	estimated	-	[Hinrikus et al., 2004]

Measurement and calculation details

The average field power density at the skin on the left side of the head was estimated from calibration curves obtained from measuring the spatial distribution under real experimental conditions using a field strength meter. During the experiments, the stability of the radiation level was monitored.

Reference articles

Hinrikus H et al. (2004): Changes in human EEG caused by low level modulated microwave stimulation
Lass J et al. (2002): Effects of 7 Hz-modulated 450 MHz electromagnetic radiation on human performance in visual memory tasks

Exposed system:

human
partial body: head (left side)

Methods Endpoint/measurement parameters/methodology

effects on the neurological system: EEG rhythm (power in the four different EEG frequency bands: theta wave, alpha wave, beta wave I and II)

Investigated system:

investigation on living organism

Investigated organ system:

brain/CNS

Time of investigation:

before exposure
during exposure
after exposure

Main outcome of study (acc. to author)

The data support the authors' hypothesis that the effect of modulated microwaves on the EEG differs at different modulation frequencies. The microwave irradiation modulated at 14 and 21 Hz enhanced the EEG power in the alpha wave and beta wave frequencies whereas no enhancement of the EEG power was found during exposure at the modulation frequency of 7 Hz. Thus, it can be suggested that the effect of an external stimulus on brain oscillations is stronger if the frequency of the stimulus is higher or close to the physiological frequency of brain rhythms. The changes were more obvious at the beginning of the exposure segments. No changes in the EEG theta wave power were detected for any modulation frequencies.
Differences were also found in individual sensitivity to exposure.
The mechanisms of the observed effects of pulse modulated microwaves are unknown.

Study character:

medical/biological study
experimental study
full/main study
double blind study

Study funded by

Estonian Science Foundation (ETF), Estonia

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