Meng Qingshuo, Tan Xinrong, Jiang Chengyong, Xiong Yanyu, Yan Biao, Zhang Jiayi
Institutes of Brain Science, State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Department of Ophthalmology, Zhongshan Hospital, Fudan University, Shanghai, China.
Front Neurosci. 2021 Feb 25;15:616760. doi: 10.3389/fnins.2021.616760. eCollection 2021.
Eye movement is not only for adjusting the visual field and maintaining the stability of visual information on the retina, but also provides an external manifestation of the cognitive status of the brain. Recent studies showed similarity in eye movement patterns between wakefulness and rapid eye movement (REM) sleep, indicating that the brain status of REM sleep likely resembles that of awake status. REM sleep in humans could be divided into phasic REM and tonic REM sleep according to the difference in eye movement frequencies. Mice are the most commonly used animal model for studying neuronal and molecular mechanisms underlying sleep. However, there was a lack of details for eye movement patterns during REM sleep, hence it remains unknown whether REM sleep can be further divided into different stages in mice. Here we developed a device combining electroencephalogram (EEG), electromyogram (EMG) as well as eye movements recording in mice to study the eye movement patterns during sleep. We implanted a magnet beneath the conjunctiva of eye and tracked eye movements using a magnetic sensor. The magnetic signals showed strong correlation with video-oculography in head-fixed mice, indicating that the magnetic signals reflect the direction and magnitude of eye movement. We also found that the magnet implanted beneath the conjunctiva exhibited good biocompatibility. Finally, we examined eye movement in sleep-wake cycle, and discriminated tonic REM and phasic REM according to the frequency of eye movements, finding that compared to tonic REM, phasic REM exhibited higher oscillation power at 0.50 Hz, and lower oscillation power at 1.50-7.25 Hz and 9.50-12.00 Hz. Our device allowed to simultaneously record EEG, EMG, and eye movements during sleep and wakefulness, providing a convenient and high temporal-spatial resolution tool for studying eye movements in sleep and other researches in mice.
眼球运动不仅用于调整视野和维持视网膜上视觉信息的稳定性，还提供了大脑认知状态的外在表现。最近的研究表明，清醒状态和快速眼动（REM）睡眠之间的眼球运动模式存在相似性，这表明REM睡眠时的大脑状态可能类似于清醒状态。根据眼球运动频率的差异，人类的REM睡眠可分为相位性REM睡眠和紧张性REM睡眠。小鼠是研究睡眠潜在神经元和分子机制最常用的动物模型。然而，关于REM睡眠期间的眼球运动模式缺乏详细信息，因此尚不清楚REM睡眠在小鼠中是否可以进一步分为不同阶段。在这里，我们开发了一种结合脑电图（EEG）、肌电图（EMG）以及小鼠眼球运动记录的装置，以研究睡眠期间的眼球运动模式。我们在小鼠眼结膜下方植入一块磁铁，并使用磁传感器跟踪眼球运动。在头部固定的小鼠中，磁信号与视频眼动图显示出很强的相关性，这表明磁信号反映了眼球运动的方向和幅度。我们还发现，植入眼结膜下方的磁铁表现出良好的生物相容性。最后，我们检查了睡眠-觉醒周期中的眼球运动，并根据眼球运动频率区分紧张性REM和相位性REM，发现与紧张性REM相比，相位性REM在0.50Hz时表现出更高的振荡功率，在1.50-7.25Hz和9.50-12.00Hz时表现出更低的振荡功率。我们的装置能够在睡眠和清醒期间同时记录EEG、EMG和眼球运动，为研究小鼠睡眠中的眼球运动及其他研究提供了一种方便且具有高时空分辨率的工具。
