Stern S, Laties V G, Nguyen Q A, Cox C
Department of Environmental Medicine, School of Medicine and Dentistry, University of Rochester, New York, USA.
Bioelectromagnetics. 1996;17(4):279-92. doi: 10.1002/(SICI)1521-186X(1996)17:4<279::AID-BEM4>3.0.CO;2-0.
Two experiments failed to confirm the Thomas, Schrot, and Liboff report that low-intensity magnetic fields disrupted the operant behavior of rats. In their experiment, food-deprived rats were trained to press a lever to obtain food pellets under a multiple fixed-ratio (FR) 30, differential reinforcement of low rate 18-24 s (DRL 18-24) schedule. After baseline training, the rats were exposed to a 30 min treatment in a different chamber prior to behavioral testing. When the treatment consisted of a horizontal 60 Hz magnetic field at 5 x 10(-5) Telsa aligned along the north-south axis combined with a static field that reduced the background to 2.61 x 10(-5) Telsa, the rate of lever pressing in the DRL component of the multiple schedule increased reliably during the immediately following test session. Changes in responding were not observed when the rats were exposed to either the static field or the 60 Hz field independently nor during sham exposures to the fields. In the present experiments, only the combined fields, i.e., those reported to be effective, were studied in rats using the same general behavioral and exposure protocol used by Thomas et al [1986a]. In experiment 1, the 2.61 x 10(-5) Telsa was achieved by reducing the vertical component of the static field. In experiment 2, both the horizontal and the vertical components were altered to match those used by Thomas et al. In both experiments additional magnetic field conditions were also studied to ensure that threshold values were exceeded and, in experiment 2, to address concerns about the role of harmonic frequencies of the 60 Hz field. The baseline performances approximated those of Thomas et al. Performances were compared between exposure, sham-exposure and control sessions. None of the exposure conditions altered any of the behavioral measures. The reasons for failing to replicate the results of Thomas et al. remain unknown.
两项实验未能证实托马斯、施罗特和利博夫的报告，即低强度磁场会干扰大鼠的操作性行为。在他们的实验中，将食物匮乏的大鼠训练成在多重固定比率（FR）30、低比率18 - 24秒差异强化（DRL 18 - 24）的时间表下按压杠杆以获取食物颗粒。在基线训练后，大鼠在行为测试前于另一个实验箱中接受30分钟的处理。当处理包括一个沿南北轴排列的5×10⁻⁵特斯拉的水平60赫兹磁场与一个将背景磁场降低到2.61×10⁻⁵特斯拉的静磁场组合时，在紧接着的测试阶段，多重时间表的DRL部分中杠杆按压速率可靠地增加了。当大鼠单独暴露于静磁场或60赫兹磁场时，以及在对磁场进行假暴露期间，均未观察到反应变化。在本实验中，仅使用托马斯等人[1986a]所采用的相同一般行为和暴露方案，对大鼠研究了组合磁场，即那些据报道有效的磁场。在实验1中，通过降低静磁场的垂直分量达到2.61×10⁻⁵特斯拉。在实验2中，水平和垂直分量均被改变以匹配托马斯等人所使用的分量。在两个实验中还研究了额外的磁场条件，以确保超过阈值，并且在实验2中，以解决对60赫兹磁场谐波频率作用的担忧。基线表现接近托马斯等人的表现。在暴露、假暴露和对照阶段之间比较了表现。没有任何暴露条件改变任何行为指标。未能重复托马斯等人结果的原因仍然未知。
