Polysomnography in humans and animal models: basic procedures and analysis

Sleep is one of the great mysteries of life. We spend a third of our life sleeping without awareness of the outside world. Part of this time, during dreams, we have a bizarre cognitive activity disconnected from reality and guided by internal stimuli. In the last 70years, as a result of basic research, there has been a remarkable increase in the knowledge of the physiology of sleep. Some of this knowledge has been transferred to the medical practice, where about 80 different sleep disturbances have been described. In most mammals (including humans) and birds, two sleep states can be readily distinguished: rapid eye movement sleep and nonrapid eye movement sleep. Polysomnography (PSG) is the basic tool used to recognize and characterize these behavioral states, and to explore brain activity during sleep. In the present work, we present a brief review of the main PSG procedures and data analysis in clinical and humans research settings, as well as in animal models.