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. 2022 Apr 27;13:856697. doi: 10.3389/fpsyg.2022.856697

FIGURE 1.

FIGURE 1

The influence of different functional brain states on EEG microstates. (1) Instructing subjects to focus their thoughts on an autobiographical memory increased duration and occurrence of one microstate, while focusing the attention on a serial subtraction task increased duration and occurrence of another microstate. Source localization attributed the memory-specific microstate to the lateral parietal lobe and the arithmetic-specific microstate to the activity of a frontoparietal network (Figure modified with permission from Bréchet et al., 2019). (2) Compared to placebo, six weeks of digital meditation training led to a reconfiguration of two of the four predominant microstates whose generators were found in the superior frontal gyrus, the superior temporal gyrus, the insula, the left inferior, and the right superior parietal lobule (Figure modified with permission from Bréchet et al., 2021). (3) EEG microstates during dreaming: compared to awake, Non-Rapid Eye Movement Sleep (NREM), dominated by slow-wave activity, selectively increased the Global Explained Variance and duration of two out of five microstates which were localized in the medial and middle frontal gyrus and the posterior cortex and midbrain, respectively. Interestingly, dreaming during NREM sleep further increased the presence of the frontal microstate but decreased the presence of the posterior microstate, indicating a local awakening (less slow-wave) of the posterior cortex (Figure modified with permission from Bréchet et al., 2020). (4) EEG microstate during global anesthesia. All five microstates identified in this study were modulated in the same way by different levels of Propofol: they first showed an increase in occurrence and complexity and decrease in duration with moderate sedation, but an inverted behavior with deeper sedation. This u-shaped behavior might be linked to the paradoxical excitation induced by moderate levels of Propofol. OAAS refers to the Observer’s Assessment of Alertness/Sedation scale ranging from 5 (awake) to 0 (deep anesthesia) (Figure modified with permission from Artoni et al., 2022).