With the widespread use of electrical equipment, cognitive functions such as working memory (WM) could be severely affected when people are exposed to 50 Hz electromagnetic fields (EMF) for long term. However, the effects of EMF exposure on WM and its neural mechanism remain unclear. In the present paper, 15 rats were randomly assigned to three groups, and exposed to an EMF environment at 50 Hz and 2 mT for a different duration: 0 days (control group), 24 days (experimental group I), and 48 days (experimental group II). Then, their WM function was assessed by the T-maze task. Besides, their local field potential (LFP) in the media prefrontal cortex (mPFC) was recorded by the in vivo multichannel electrophysiological recording system to study the power spectral density (PSD) of θ and γ oscillations and the phase-amplitude coupling (PAC) intensity of θ-γ oscillations during the T-maze task. The results showed that the PSD of θ and γ oscillations decreased in experimental groups I and II, and the PAC intensity between θ and high-frequency γ (hγ) decreased significantly compared to the control group. The number of days needed to meet the task criterion was more in experimental groups I and II than that of control group. The results indicate that long-term exposure to EMF could impair WM function. The possible reason may be the impaired communication between different rhythmic oscillations caused by a decrease in θ-hγ PAC intensity. This paper demonstrates the negative effects of EMF on WM and reveals the potential neural mechanisms from the changes of PAC intensity, which provides important support for further investigation of the biological effects of EMF and its mechanisms.
随着电气设备的广泛应用，长期处于50 Hz的电磁场（EMF）环境可能会使工作记忆（WM）等认知功能受到严重影响。然而，EMF影响WM的效应及其神经机制尚不明确。为此本文将15只大鼠随机分为三组，分别暴露于50 Hz、2 mT的EMF环境0 d（对照组）、24 d（实验Ⅰ组）和48 d（实验Ⅱ组），通过T-迷宫任务评估其WM水平，并基于在体多通道电生理记录系统获取内侧前额叶皮层（mPFC）的局部场电位（LFP），分析任务过程中θ和γ节律振荡的功率谱密度（PSD）变化，以及θ-γ节律的相位幅值耦合（PAC）强度变化。结果显示，实验Ⅰ组和Ⅱ组大鼠的θ和γ节律PSD均有不同程度下降，θ和高频γ（hγ）之间的PAC强度下降；实验Ⅰ组和Ⅱ组大鼠达到WM任务标准所需时长均高于对照组。结果表明EMF长期暴露损害了WM功能，可能的原因是θ-hγ的PAC强度下降引起的mPFC不同节律振荡之间的信息交流受损。本文从PAC强度变化的角度揭示了EMF对WM造成负面影响的潜在神经机制，为进一步探究EMF生物效应及其作用机制提供了重要支持。.
Keywords: Electromagnetic field; Local field potential; Media prefrontal cortex; Phase-amplitude coupling; Working memory.