EEG and EMG recording system for sleep study with a freely moving rat

다국어 초록 (Multilingual Abstract)

Sleep is known to play an important role in cognitive functions as well as in physical recovery. Especially, high-quality sleep is closely associated with smooth sleep cycles between NREM (non-rapid eye movement) and REM (rapid eye movement) sleep. It is well known that both sleep stages show clear distinction in electroencephalogram (EEG) and electromyogram (EMG) signals. Therefore, as a first step for sleep study with rodents, a sleep monitoring system must be established for stable measurement of EEG and EMG. There are two challenges for the setup. First, animals should be able to freely move without interruption of EEG or EMG recording cable, so that their natural behavior and sleep can occur. Second, long-term EEG and EMG should be recorded stably. Also, the movements of animals can cause a cable tension and moving artifacts. The movement-related artifacts can interfere with judgment of sleep stages. Also, rodent gnawing of the recording cable frequently leads to early termination of sleep study. In this study, in order to overcome these problems, acrylic cages were developed for sleep monitoring which can minimize the interruption of cables and the artifacts. Principle of lever mechanics is applied to rotational cover of the cage, and it rotates vertically in synchronization with rat’s movement. When the rat stand up, the cage cover opens up to prevent the cable from loosening. Therefore, cable tension can be stably maintained, allowing the rat to move freely without causing artifact. As a result, long-term EEG and EMG recordings are successful performed, and specific characteristics of each sleep stages can be extracted due to the high-quality recorded signals. We expected that the developed sleep monitoring setup can be applied to various long-term in vivo experiments with rats.