This book discusses the evolution of sleep and its possible function in the higher invertebrates and vertebrates, including humans. It describes the current concept of sleep and its functions, based on research on the mammalian system. To date, electrophysiological recordings of the brain waves, muscle activity, and eye movements are the only tools available for characterizing the sleep architecture in the majority of animals. In mammals and birds, only two distinct types of sleep are found – non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Since the discovery of...