Figure 2.

Muscle tone, sleep stages and SWA. Time course of (A) EMG variance (i.e. total power), (B) sleep profile (MT, movement time; 1 to 4, NREMS stages 1 to 4), and (C) slow-wave activity (SWA) of an individual for a night and a morning sleep episode. The horizontal red lines in A indicate the threshold that was predetermined to identify episodes of low muscle tone (see Methods). Note the episodes with low level of EMG variance during NREMS at sleep onset (red arrow) and later in the night. In the morning, the episodes of NLMT are longer than in night sleep and often, the muscle tone remained low during the entire recording.