Scientific Reports
October 13, 2020
Lucie Bréchet, Denis Brunet, Lampros Perogamvros et al.
92 citations
During non-rapid eye movement (NREM) sleep, brief brain states lasting less than a second, called EEG microstates, determine whether a person will recall a dream upon waking. Two microstates (3 and 4) dominated NREM sleep compared to wakefulness. Within NREM sleep, microstate 3 was more present before dream recall, while microstate 4 was less present. Microstate 3 involved the medial frontal lobe, suggesting deeper local deactivation and executive disconnection that keeps the brain asleep. Microstate 4 involved the occipital cortex, thalamus, and brainstem, and its reduced presence may indicate local activation enabling rich perceptual dream content. The temporal dynamics of these alternating brain states determine whether conscious experience arises during NREM sleep.
Frontiers in Psychology
April 27, 2022
Lucie Bréchet, Christoph M. Michel
41 citations
Conscious experience feels continuous but actually consists of brief, discrete brain states lasting 60–120 milliseconds, called EEG microstates. These stable scalp electric field patterns, measured with high temporal resolution, may represent the basic building blocks of thought. Altered states of consciousness—including sleep, anesthesia, meditation, and psychiatric conditions—change the dynamics of these microstates. This perspective argues that studying EEG microstates can reveal underlying features of self-consciousness, summarizing recent findings on microstate alterations during mind-wandering, meditation, sleep, and anesthesia.
Brain Connectivity
March 1, 2021
Lucie Bréchet, David A Ziegler, Alexander J. Simon et al.
After six weeks of breath-focused, digital meditation training, young adults showed changes in resting-state brain networks measured by EEG microstates, particularly in the right insula, superior temporal gyrus, superior parietal lobule, and superior frontal gyrus bilaterally. These topographical changes were not seen in an active placebo control group. The results suggest that this low-cost, digital meditation practice can reorganize brain network connectivity and may offer a novel, noninvasive approach for treating neuropathological conditions.
Neuroimage
July 1, 2019
Lucie Bréchet, Denis Brunet, Gwénaël Birot et al.
The study used ultra-high field fMRI and high-density EEG to investigate the neural basis of self-generated thoughts. Participants engaged in two conditions: retrieving self-relevant past memories or performing serial mental arithmetic. fMRI showed increased activity in temporal, parietal, and occipital areas during memory retrieval, organized into subsystems for scene reconstruction and self-experience. EEG microstate analysis revealed that specific brief periods of stable brain activity were modulated differently between conditions, linking these fast temporal dynamics to the slower fMRI changes. The findings suggest that fMRI networks related to mental activity can be captured by EEG as brief, recurring periods of coherent neuronal activity.
Frontiers in Behavioral Neuroscience
January 1, 2018
Lucie Bréchet, Petr Grivaz, Baptiste Gauthier et al.
The inferior parietal lobule, particularly the angular gyrus, may be a shared brain region for both bodily self-consciousness—the sense of being located in a body and experiencing the world from a first-person perspective—and episodic autobiographical memory, the conscious reliving of past events. An anatomical overlap in the angular gyrus was found bilaterally when comparing a prior study on spatial aspects of bodily self-consciousness with a new meta-analysis of functional neuroimaging studies on episodic autobiographical memory. No overlap appeared with semantic autobiographical memory, which involves factual knowledge about one's past. These preliminary findings suggest the bilateral angular gyrus is a key structure for both online self-awareness and the re-experiencing of personal memories.
Fiorenzo Artoni, Julien Maillard, Juliane Britz et al.
preprint
The stream of consciousness is thought to be composed of discrete brain states, reflected in EEG microstates—transient, stable patterns of global neuronal activity lasting fractions of seconds. In 23 surgical patients, high-density EEG was recorded continuously from wakefulness to unconsciousness induced by step-wise increasing propofol concentrations. Under surgical anesthesia, microstate sequences became sparser, longer-lasting, and less complex. However, moderate sedation initially increased the temporal dynamics and complexity of microstates, producing a distinctive U-shaped pattern that may correspond to paradoxical excitation. These findings suggest that normal consciousness relies on a metastable balance between order and chaos, enabling flexible state transitions, and that altered consciousness reflects changes in this balance.