Reduced repertoire of cortical microstates and neuronal ensembles in medically-induced loss of consciousness

Abstract

SUMMARYMedically-induced loss of consciousness (mLOC) has been linked to a macroscale break-down of brain connectivity, yet the neural microcircuit correlates of mLOC remain unknown. We applied non-linear t-stochastic neighbor embedding (t-SNE) and Lempel-Ziv-Welch complexity analysis to two-photon calcium imaging and local field potential (LFP) measurements of cortical microcircuit activity across anesthetic depth in mice, and to micro-electrode array recordings in human subjects.We find that mLOC disrupts population activity patterns by i) a reduction of discriminable network microstates and ii) a reduction of independent neuronal ensembles. These alterations are not explained by a simple reduction of neuronal activity and reveal abnormal functional microcircuits. Thus, normal neuronal ensemble dynamics could contribute to the emergence of conscious states.

Complexity and 1/f slope jointly reflect brain states

“…It has been shown that LZc decreases concomitantly with the loss of phenomenological possibilities, which is consistent with theoretical views of consciousness (Tononi & Edelman, 1998). Lempel-Ziv complexity algorithm computes the number of non-redundant segments of a signal (Lempel & Ziv, 1976), which in turn, when applied to brain data, is related to the abundance of the repertoire of brain activity patterns observed (Wenzel et al, 2019). During the transition from wakefulness to sleep or anesthesia, the number of possible experiences and cognitive processes that one can have is greatly reduced.…”

“…The slope of the spectral power law has been linked to E/I balance (Lombardi et al, 2017), while LZc reflects the vastness of the repertoire of brain activity patterns (Wenzel et al, 2019). Although these two measures may seem unrelated at first, we hypothesize that both reflect a specific type of entropy of cortical systems.…”

“…Thus, it is expectable that the complexity of brain activity follows the same pattern. In fact, this reduction of the repertoire of brain activity has been seen in rats at the single neuron level using a myriad of convergent measures of cortical diversity, including LZc (Wenzel et al, 2019) which suggests that LZc can be applied as a multiscale proxy of neural repertoire.…”

Measuring stimulus-evoked neurophysiological differentiation in distinct populations of neurons in mouse visual cortex

“…Theoretical work has demonstrated that ND can serve as a proxy for integrated information in highly recurrent systems where integration can be assumed, such as the brain (Marshall et al, 2016). Consistent with IIT's predictions, several studies have employed differentiation analysis across a range of species and spatiotemporal scales to show that loss of ND is implicated in loss of consciousness (Casali et al, 2013;Hudetz et al, 2014;Barttfeld et al, 2015;Wenzel et al, 2019).…”

Single-cell Networks Reorganise to Facilitate Whole-brain Supercritical Dynamics During Epileptic Seizures

“…Furthermore, our data indicate that supercritical networks cause increased population covariance which reduces the number of metastable states. Given the evidence for reduced brain state diversity during a loss of awareness induced by general anaesthesia (Schartner et al, 2015;Wenzel et al, 2019), we hypothesise that impaired metastability may explain the loss of awareness that occurs during generalised seizures (Blumenfeld & Taylor, 2003). In this way, supercritical networks may give rise to brain dysfunction in epilepsy.…”