Effects of exposures to weak 2-Hz vs. 8-Hz electromagnetic fields on spectral characteristics of the electroencephalogram in afternoon nap

The human brain seems to be able to respond to low-level extremely low-frequency electromagnetic fields. Controlled laboratory studies of human sleep under exposure to such fields are scarce, especially on the effects of 1 Hz - 16 Hz fields overlapping with the frequencies of the electroencephalographic (EEG) signal (e.g., delta, theta, alpha, and sigma activities). In a double-blind placebo-controlled study, we examined the effects of exposure to low-level electromagnetic fields of frequencies 2 Hz and 8 Hz on the EEG power density spectra in the range from 1 Hz to 16 Hz and sleep structure. Sleep of 14 young healthy volunteers was polysomnographically recorded during three 50-min afternoon naps (either without exposure or with 2 Hz/0.004 mu T or 8 Hz/0.004 mu T electromagnetic field). During the first 30 min of a nap the sham, 2 Hz or 8 Hz/0.004 mu T exposures had the same effect. For the remaining 20 min, amount of stage 3 sleep and powers in 1 Hz-8 Hz range continued to build up under the 8 Hz/0.004 mu T and, especially, under the 2 Hz/0.004 mu T exposure, whereas they did not change in the sham condition. Therefore, the low-level 2 Hz electromagnetic fields might stimulate deep sleep in the afternoon nap.