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The neuroscience of sleep is the study of the neuroscientific and physiological basis of the nature of sleep and its functions. Traditionally, sleep has been studied as part of psychology and medicine. The study of sleep from a neuroscience perspective grew to prominence with advances in technology and proliferation of neuroscience research from the second half of the twentieth century. The fact that organisms daily spend hours of their time in sleep and that sleep deprivation can have disastrous effects ultimately leading to death, demonstrate the importance of sleep. For a phenomenon so important, the purposes and mechanisms of sleep are only partially understood, so much so that as recently as the late 1990s it was quipped: "The only known function of sleep is to cure sleepiness". However, the development of improved imaging techniques like EEG, PET and fMRI, along with high computational power have led to an increasingly greater understanding of the mechanisms underlying sleep. The fundamental questions in the neuroscientific study of sleep are - # What are the correlates of sleep i.e. what are the minimal set of events that could confirm that the organism is sleeping? # How is sleep triggered and regulated by the brain and the nervous system? # What happens in the brain during sleep? # How can we understand sleep function based on physiological changes in the brain? # What causes various sleep disorders and how can they be treated? Other areas of modern neuroscience sleep research include the evolution of sleep, sleep during development and aging, animal sleep, mechanism of effects of drugs on sleep, dreams and nightmares, and stages of arousal between sleep and wakefulness. ==Introduction == (詳細はconsciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. In mammals and birds, sleep is broadly divided into two types- rapid eye movement (REM) and non-rapid eye movement (NREM or non-REM) sleep. NREM sleep itself is divided into multiple stages- N1, N2 and N3. Sleep proceeds in cycles of REM and NREM, the order normally being N1 → N2 → N3 → N2 → REM. Of the two, NREM is considered to be deep sleep (the deepest part of NREM is called slow wave sleep), and is characterized by lack of prominent eye movement or muscle paralysis. On the other hand, REM sleep is considered closer to wakefulness and is characterized by rapid eye movement and muscle atonia. It is during REM sleep that dreams (or nightmares) occur. Sleep timing is controlled by the circadian clock, and in humans, to some extent by willed behavior. The term circadian comes from the Latin ''circa'', meaning "around" (or "approximately"), and ''diem'' or dies, meaning "day". The circadian clock refers to a biological mechanism that governs multiple biological processes causing them to display an endogenous, entrainable oscillation of about 24 hours. These rhythms have been widely observed in plants, animals, fungi and cyanobacteria. Sleep is considered an essential function for animals, though it is not yet sure why this is so. However, sleep deprivation can lead to drastic consequences, and inadequate sleep can lead to sleep debt. Also, sleep at any time of the day is not equivalent and it is most effective only when it coincides with certain biological processes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Neuroscience of sleep」の詳細全文を読む スポンサード リンク
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