REM sleep EEG pattern: Examination by a new EEG scoring system for REM sleep period

The pattern of rapid eye movement (REM) sleep was examined using a new scoring system for electroencephalogram (EEG) stages. An all-night polysomnogram (PSG) was recorded from 12 young healthy volunteers. First, all the data were scored according to the standard criteria of Rechtschaffen and Kales’ A Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects (1968), and epochs of typical REM sleep were collected. The extracted data were then re-scored for each 5 s using the criteria of seven EEG stages of REM sleep: (1) alpha wave, train; (2) alpha wave, intermittent A; (3) alpha wave, intermittent B; (4) EEG flattening; (5) theta wave; (6) sawtooth wave; and (7) movement time. The results showed that the EEG flattening (4) and theta wave stages (5) occupied 92.7% of the epochs of REM sleep. The most frequent transition pattern was also between these two stages (71.1%), and these stages rarely transitioned to other stages. The number of stage continuations within 2 epochs (10 s) was largest in EEG stage 4, and those in stage 5 followed it (64.5% and 54.2%, respectively). EEG stages 4 and 5 sometimes lasted for more than 13 epochs (over 1 min). The number of stages containing sawtooth waves was less than expected, and was more frequent at the beginning than at the end of REM sleep. The distinguishing feature of the REM sleep EEG pattern was the stability of the stages of EEG flattening and theta wave, compared with the sleep onset period EEG pattern.