この研究は、ヒトの認知タスク遂行能力に対する50 Hz、100 μTの磁界ばく露の直接的影響および遅発的影響を調べた。80人の被験者が、視覚的持続時間弁別タスクを完了した。タスク遂行中に、半数は磁界ばく露を受け、もう半数は擬似ばく露を受けた。遅発的影響は、弁別タスク完了の直後に続けて実施した認知記憶タスクで調べた。その結果、著者の以前の研究とは異なり、視覚弁別タスクの反応時間および正確さに対する磁界ばく露の影響は見られなかった；しかし、磁界ばく露による遅発的影響が記憶について見られた（認知の正確さを低下させた）、と報告している。著者は、長年の実験の結果として、磁界の影響を信頼性高く引き出すような磁場パラメータとタスク遂行能力尺度との組み合わせを見つけることは、とらえどころがないことが証明されつつあると結論している。
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The direct and delayed effects of exposure of subjects to a 50 Hz magnetic field on cognitive performance should be investigated.
The findings of Whittington et al. 1996, who found a significantly decreased reaction time in probands after exposure to a 50 Hz magnetic field, should be reproduced while being extended to investigate the delayed effects on recognition memory.
80 subjects participated in the study, 30 males and 50 females aged between 19 and 53 years, one half being exposed to the magnetic field (exposure group) and the other half being sham exposed (sham exposure group). Each group was subsequently equally divided into a morning and an afternoon session to account for potential time of day effects. A preliminary analysis revealed no time of day effects. Therefore, the data from morning and afternoon sessions were combined for the analysis of all test parameters.
ばく露時間: intermittent (1 s on, 1 s off) for 11 minutes
|ばく露時間||intermittent (1 s on, 1 s off) for 11 minutes|
|チャンバの詳細||4.5 x 5.5 m unshielded room, plastic chair with adjustable head rest|
|ばく露装置の詳細||a set of Helmholtz coils (radius = 0.2 m) was suspended in each of four adjacent booths, such that each coil set was positioned at right angles to the sets on each side; the coils were wound onto a wooden form, each coil having 120 turns of 1.5 mm resin coated copper wire; the booths were constructed entirely from non-metallic materials; there was no detectable noise or vibration from the coils|
|Sham exposure||A sham exposure was conducted.|
|磁束密度||100 µT||effective value||測定値||-||-|
The recognition memory performance and decision confidence were significantly reduced in exposed subjects compared to sham exposed subjects.
No significant differences in reaction time and decision accuracy were found between exposed and sham exposed individuals in the visual duration discrimination assay. Hence, the results from Whittington et al. 1996 could not be confirmed.
Subjects and experimentators could not distinguish between exposure and sham exposure, thus ensuring the double-blind procedure.
As previous findings could not be reproduced but new possible effects were found, the authors conclude that it might be difficult to find reliable parameters for the investigation of effects of exposure to a 50 Hz magnetic field on the cognitive performance.