Processed EEG in natural sleep.

Sleep stages are conventionally scored according to recommendations by a committee chaired by Rechtschaffen and Kales in 1968. With these rules normal sleep is divided into rapid eye movement sleep and non-rapid eye movement sleep. Non-rapid eye movement sleep is subdivided into four further stages. With the Rechtschaffen and Kales scoring system the dominant sleep stage at any one time is scored. However, the dynamic structure of sleep is not adequately shown. Furthermore, there is considerable interscorer variability, the scoring is time consuming, tedious and difficult to perform. To overcome these limitations automatic sleep scoring devices using processed EEG technology are developed. These developments are discussed in this chapter.