[LINK] electromagnetic fields effect brain activity.
stephen at melbpc.org.au
Fri Dec 29 01:38:02 AEDT 2006
It's astonishing how sense-evolved human minds are.
Here's a definitive Swiss study, published June 2006
in the Journal Environmental Health Perspectives and
a Project awarded by the Swiss Research Foundation.
Effect of electromagnetic fields (EMF) on sleep, sleep EEG, and regional cerebral blood flow
In view of the very limited available data related to the exposure to personal telecommunication devices, the need for human laboratory research in volunteers including sleep studies was recognized.
Therefore, the () University of Zurich and IT'IS performed experimental sleep studies at the PET-Center of the University Hospital.
Study 1: Intermittent night-time exposure
In a first study, 24 subjects were exposed intermittently (15 min on - 15 min off) to electromagnetic fields of mobile phones while asleep. The maximum exposure intensity was set not to exceed half of the value of the international exposure limit. Compared to a sham condition without exposure, the following effects were observed: 1) The brain waves (sleep EEG) were altered in a specific frequency range (7 - 14 Hz). These changes appeared rapidly and subsided in the course of the night. 2) Waking after sleep onset was reduced.
Study 2: Unilateral exposure prior to daytime sleep
The previous results prompted us to perform a study in which 16 subjects were exposed to electromagnetic fields of mobile phones for 30 min prior to daytime sleep. The sleep EEG was affected in the same frequency range (9 - 14 Hz) as for exposure during sleep. The effect subsided in the course of the sleep episode. Sleep duration was not affected.
Study 3: Unilateral exposure to pulse-modulated and continuous-wave EMF
We investigated whether pulse modulation of the signal is critical for the EEG effect in 16 healthy men. Pulse-modulated EMF enhanced power in the alpha frequency range in the waking EEG prior to sleep onset and in the spindle frequency range (12 - 14 Hz) during stage 2 sleep. The effect was most pronounced in the second part of the night. EMF without pulse modulation did not enhance power in the waking or sleep EEG. Sleep duration and sleep stages were not affected. The results showed for the first time that pulse modulation of the EMF is necessary to induce changes in the waking and sleep EEG.
Study 4: Exposure during waking: Positron emission tomography (PET) study
We also addressed the question whether exposure to EMF modifies regional cerebral blood flow (rCBF). PET scans were taken after unilateral head exposure for 30 min in 13 subjects. Compared to sham exposure, regional rCBF was increased in the dorsolateral prefrontal cortex of the exposed hemisphere after "handset-like" EMF exposure.
The results demonstrate that high frequency electromagnetic fields affect brain physiology as assessed by measures of cerebral blood flow and brain electrical activity.
Effects of EMF on the sleep EEG were consistently observed in three studies under similar, yet different experimental conditions: exposure before sleep vs. exposure during sleep; unilateral exposure vs. exposure of the entire head; exposure to different modulation schemes.
The studies do not allow conclusions about possible adverse effects of EMF exposure on human health.
In future studies, varying the modulation characteristics of the signal will help to specify the critical frequencies
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