Abstract
Different levels of brain arousal can be delineated not only during sleep but also during wakefulness. Electroencephalography (EEG) is the gold standard to assess different levels of brain arousal. A novel EEG- and electrooculography (EOG)-based tool, the Vigilance Algorithm Leipzig (VIGALL 2.0), allows determining the level of EEG-vigilance (indicating brain arousal). Considering the frequency patterns and LORETA-based cortical distribution of electroencephalic activity, VIGALL 2.0 automatically attributes one out of seven vigilance stages to each EEG segment (1-sec EEG segments by default), ranging from high alertness (stage 0), to relaxed wakefulness (stage A1 to A3), to drowsiness (stage B1 to B2/3) up to sleep onset (stage C). Building on the time series of these seven vigilance stages across 20 min, two parameterizations of the temporal dynamic (brain arousal regulation) are calculated: the lability score and the slope index. 27 healthy participants (age = 22.93 ± 3.44 years, 18 females) underwent two sessions (7 days apart) of a twenty-minute eyes-closed resting EEG paradigm. The test-retest reliability coefficients for the EEG-vigilance stages were between rho = .53 and .86 (all p < .01). For the temporal dynamic of the stages across 20 min, the test-retest reliability coefficients were rho = .70 (lability score, p < .001) and .71 (slope index, p < .001). This study demonstrated some trait aspects of brain arousal regulation by confirming the stability of temporal dynamic of EEG-vigilance stages as assessed with VIGALL 2.0. Considering the “first day in lab” effect identified in the present study, more adaptation to the lab surrounding and a stricter control of other state factors should be taken into account, which might improve reliability. Additionally, in a clinical context, a broader range of brain arousal regulation patterns might be found, possibly leading to higher test-retest reliability than was found in this homogenous healthy sample. This would be desirable, as parameters of brain arousal regulation are promising diagnostic and prognostic biomarkers for diseases with arousal disturbances, such as affective disorders, ADHD and fatigue.
Highlights
Different levels of brain arousal can be delineated during sleep and during wakefulness
Arousal regulation denotes the adaptation of brain arousal to situational requirements, which is of most importance for efficient human behavior
Having in mind the potential use of EEG parameters of brain arousal regulation as diagnostic or predictive biomarkers, the aim of this study was to assess the testretest reliability of lability score, slope index, EEG-vigilance stages and mean EEGvigilance level as assessed by Vigilance Algorithm Leipzig (VIGALL) in healthy subjects
Summary
Different levels of brain arousal can be delineated during sleep and during wakefulness. Considering the frequency patterns and LORETA-based cortical distribution of electroencephalic activity, VIGALL 2.0 automatically attributes one out of seven vigilance stages to each EEG segment (1-sec EEG segments by default), ranging from high alertness (stage 0), to relaxed wakefulness (stage A1 to A3), to drowsiness (stage B1 to B2/3) up to sleep onset (stage C). Different levels of brain arousal can be delineated during sleep (e.g. Iber et al 2008; Rechtschaffen and Kales 1969) and during wakefulness (see below). By taking into account the frequency patterns as well as the Low Resolution Electromagnetic Tomography (LORETA)-based cortical distribution of EEG activity, different EEG-vigilance stages (indicating brain arousal states) can be distinguished during the transition from high alertness to relaxed wakefulness, to drowsiness up to sleep onset
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