この研究は、ボランティア誘発実験で、0.25 - 0.8Hzでパルス変調された高周波電磁界（RF EMF、搬送周波数900 MHz）ばく露が、睡眠中の脳電図（EEG）の特性を変化させるか否かを調べた。特に、タスク遂行成績の睡眠による改善は睡眠スピンドル（12〜15 Hz）および睡眠徐波活動（SWA、0.75〜4.5 Hz）と密接に関連することに着目し、RF EMFによる睡眠中の皮質活動の変化とタスク遂行成績の睡眠による変化の相互作用を分析した。16人の男性被験者は2回の終夜実験に参加した。１回は一晩中、パルスRFEMFばく露を、もう１回は擬似ばく露を実施し、終夜EEGを記録した。また、両実験の夕方および翌朝、運動シーケンスタスクを遂行した。その結果、両方の条件下で、すべての被験者は良好な睡眠の質を得た（平均睡眠効率1 > 90 %）；パルスRFEMFばく露夜は、擬似ばく露夜に比べ、睡眠期間の終わりにかけてのSWA増加が有意であった；スピンドルの活動への影響は見られなかった；さらに、SWA中にRF EMFバースト関連応答が増加した；パルスRFEMFばく露夜は、擬似ばく露夜に比べ、運動シーケンスタスク遂行成績の睡眠による改善の程度が有意に減少した（-20.1 %）;総括すると、RF EMFと睡眠中の皮質興奮性の繰り込みとの相互作用の結果、ばく露夜にはSWAの時間経過が変化し、それがタスク遂行成績の睡眠による改善に悪影響を及ぼした可能性がある、と報告している。
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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.
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).
Modulation type: pulsed
ばく露時間: 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
|ばく露時間||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|
|Pulse width||7.1 ms|
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.
|Distance between exposed object and exposure source||415 mm|
|ばく露装置の詳細||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.|
|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|
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.