Table 2.

Scoring criteria of EEG vigilance stages (see the VIGALL 2.1 manual [33] for detailed description); higher scores correspond to higher arousal levels

EEG characteristic	VIGALL stage classification	Stage score
Low amplitude, predominantly beta EEG (12–25 Hz) without horizontal SEM	0	7
Alpha frequency (8–12 Hz), dominant in occipital regions	A1	6
Alpha frequency (8–12 Hz), dominant in parietal regions	A2	5
Alpha frequency (8–12 Hz), dominant in frontal regions	A3	4
Low amplitude, predominantly beta EEG (12–25 Hz) with horizontal SEM	B1	3
Predominantly delta (2–4 Hz) or theta (4–7 Hz) EEG	B2/3	2
K-complexes or sleep spindles	C	1

VIGALL 2.1 Vigilance Algorithm Leipzig 2.1, EEG electroencephalogram, SEM slow eye movements