Study type: Medical/biological study (experimental study)

Stimulation of the brain with radiofrequency electromagnetic field pulses affects sleep-dependent performance improvement. med./bio.

Published in: Brain Stimul 2013; 6 (5): 805-811

Aim of study (acc. to author)

To study possible mechanisms how radiofrequency electromagnetic fields affect cortical activity during sleep and to test whether such effects on cortical activity during sleep interact with sleep-dependent performance changes.

Background/further details

Sleep-dependent performance improvements seem to be closely related to sleep spindles (12-15 Hz) and sleep slow-wave activity (0.75-4.5 Hz). In previous studies (see "related articles"), pulse modulated radiofrequency electromagnetic fields (900 MHz) were capable to modulate these EEG characteristics of sleep. A sleep spindle is a burst of oscillatory brain activity visible on an EEG that occurs during sleep stage 2. It consists of 12-14 Hz waves that occur for at least 0.5 seconds.
16 male subjects (18-21 years) underwent two experimental nights (one exposure night, one control night).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 900 MHz
Modulation type: pulsed
Exposure duration: intermittent during 8 h (during the sleep; exposure of 5 min "Intermittent-1" was followed by 1 min with no exposure (OFF phase), then 5 min "Intermittent-2" was followed by a 7 min OFF phase; this 18 min sequence was repeated throughout the whole night
  • SAR: 0.15 W/kg spatial average (10 g) (peak spatial SAR during the whole night)
  • SAR: 10 W/kg spatial average (10 g) (peak spatial SAR during the 7.1 ms pulses)
  • SAR: 1 W/kg (500 ms burst average)
  • SAR: 0.125 W/kg ("Intermittent-1" average)
  • SAR: 0.4 W/kg ("Intermittent-2" average)

Exposure 1

Main characteristics
Frequency 900 MHz
Type
Exposure duration intermittent during 8 h (during the sleep; exposure of 5 min "Intermittent-1" was followed by 1 min with no exposure (OFF phase), then 5 min "Intermittent-2" was followed by a 7 min OFF phase; this 18 min sequence was repeated throughout the whole night
Modulation
Modulation type pulsed
Pulse width 7.1 ms
Additional info

7 consecutive 7.1 ms pulses forming one 500 ms burst; these 500 ms bursts were repeated every 4 s ("Intermittent-1" phase, 0.25 Hz, corresponding approximately to occurrence of sleep spindles), and every 1.25 s ("Intermittent-2" phase, 0.8 Hz, corresponding approximately to frequency of slow oscillations), respectively.

Exposure setup
Exposure source
Distance between exposed object and exposure source 415 mm
Setup circular-polarized antenna mounted on the wall at a height of 490 mm above the matress and facing down toward the volunteer's forehead
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 0.15 W/kg spatial average - 10 g peak spatial SAR during the whole night
SAR 10 W/kg spatial average - 10 g peak spatial SAR during the 7.1 ms pulses
SAR 1 W/kg - - - 500 ms burst average
SAR 0.125 W/kg - - - "Intermittent-1" average
SAR 0.4 W/kg - - - "Intermittent-2" average

Reference articles

  • Christ A et al. (2010): The Virtual Family--development of surface-based anatomical models of two adults and two children for dosimetric simulations.

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)

Good sleep quality was obtained in all subjects under both conditions (exposure and sham exposure). After pulsed radiofrequency electromagnetic field exposure an increased slow wave activity during exposure compared to sham exposure was found toward the end of the sleep period. Spindle activity was not affected. Moreover, subjects showed an increased electromagnetic field burst-related response in the slow wave activity range, indicated by an increase in event-related EEG spectral power (ERD/ERS) and phase changes (ITC) in the slow wave activity range.
Under exposure, sleep-dependent performance improvement in the motor task was reduced compared to the sham exposure condition .
The study showed that a radiofrequency electromagnetic field exposure may directly affect ongoing brain activity during sleep, and as a consequence alter sleep-dependent performance improvement.

Study character:

Study funded by

Related articles