EEG Microstates in Altered States of Consciousness

Abstract

Conscious experiences unify distinct phenomenological experiences that seem to be continuously evolving. Yet, empirical evidence shows that conscious mental activity is discontinuous and can be parsed into a series of states of thoughts that manifest as discrete spatiotemporal patterns of global neuronal activity lasting for fractions of seconds. EEG measures the brain’s electrical activity with high temporal resolution on the scale of milliseconds and, therefore, might be used to investigate the fast spatiotemporal structure of conscious mental states. Such analyses revealed that the global scalp electric fields during spontaneous mental activity are parceled into blocks of stable topographies that last around 60–120 ms, the so-called EEG microstates. These brain states may be representing the basic building blocks of consciousness, the “atoms of thought.” Altered states of consciousness, such as sleep, anesthesia, meditation, or psychiatric diseases, influence the spatiotemporal dynamics of microstates. In this brief perspective, we suggest that it is possible to examine the underlying characteristics of self-consciousness using this EEG microstates approach. Specifically, we will summarize recent results on EEG microstate alterations in mind-wandering, meditation, sleep and anesthesia, and discuss the functional significance of microstates in altered states of consciousness.

The temporal dynamics of Large‐Scale brain network changes in disorders of consciousness: A Microstate‐Based study

“…The results were similar to our results, which showed that the lower the level of consciousness, the longer the mean duration of the microstate 24 . Lucie Bréchet et al also found that the mean duration of all microstates in the sensor level was longer under sleep and deep anesthesia 25 . The above studies further confirm that longer mean durations of microstates may represent lower brain dynamics in consciousness‐related studies.…”

“…24 Lucie Bréchet et al also found that the mean duration of all microstates in the sensor level was longer under sleep and deep anesthesia. 25 The above studies further confirm that longer mean durations of microstates may represent lower brain dynamics in consciousness-related studies.…”

Functional network dynamics revealed by EEG microstates reflect cognitive decline in amyotrophic lateral sclerosis

“…However, there remains a lack of understanding of the neural mechanisms leading to the presence of microstates and their transitions. It remains unclear how microstates actually reflect conscious thoughts, despite new insights on microstates in various states of consciousness (e.g., sleep, anaesthesia, wakefulness) (Bréchet & Michel, 2022) and rough estimations of the brain sources each microstate class originate from (Bréchet et al, 2020;Britz et al, 2010;Custo et al, 2017;Milz et al, 2017;Musso et al, 2010;Pascual-Marqui et al, 2014). The interpretation of microstates' characteristics often relies heavily on estimated brain sources.…”

Effect of topographic comparison of electroencephalographic microstates on the diagnosis and prognosis prediction of patients with prolonged disorders of consciousness

“…6 Analysis of clusters consistently reveals four configurations, called EEG microstate classes A to D. 7,8 Microstate temporal dynamics are sensitive to neuropsychiatric conditions 9,10 and altered states of consciousness. [11][12][13] Schizophrenia patients and their siblings have a higher prevalence of class C and a lower prevalence of class D. 9 All classes of Lewy body dementia have longer microstate durations in comparison with controls, but the occurrence of each class is lower than that in controls. 14 In the case of prolonged disorders of consciousness (pDoC), there were fewer classes of microstates, 15 and microstate D proved to be the most precise metric for discerning between VS/UWS and MCS.…”