Tracking Eye Movements During Sleep in Mice

Qingshuo Meng; Xinrong Tan; Chengyong Jiang; Yanyu Xiong; Biao Yan; Jiayi Zhang

doi:10.3389/fnins.2021.616760

Tracking Eye Movements During Sleep in Mice

Front Neurosci. 2021 Feb 25:15:616760. doi: 10.3389/fnins.2021.616760. eCollection 2021.

Authors

Qingshuo Meng¹, Xinrong Tan¹, Chengyong Jiang¹, Yanyu Xiong¹, Biao Yan¹, Jiayi Zhang¹

Affiliation

¹ 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.

Abstract

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.

Keywords: biocompatibility; eye movement tracking; phasic REM; sleep–wake cycle; tonic REM.