Complexity of brain dynamics as a correlate of consciousness in anaesthetized monkeys

Abstract

The use of anaesthesia is a fundamental tool in the investigation of consciousness. Anesthesia procedures allow to investigate different states of consciousness from sedation to deep anesthesia within controlled scenarios. In this study we use information quantifiers to measure the complexity of electrocorticogram recordings in monkeys. We apply these metrics to compare different stages of general anesthesia for evaluating consciousness in several anesthesia protocols. We find that the complexity of brain activity can be used as a correlate of consciousness. For two of the anaesthetics used, propofol and medetomidine, we find that the anaesthetised state is accompanied by a reduction in the complexity of brain activity. On the other hand we observe that use of ketamine produces an increase in complexity measurements. We relate this observation with increase activity within certain brain regions associated with the ketamine used doses. Our measurements indicate that complexity of brain activity is a good indicator for a general evaluation of different levels of consciousness awareness, both in anesthetized and non anesthetizes states.

Pattern Breaking: A Complex Systems Approach to Psychedelic Medicine

“…Firstly, there is now substantial evidence to support the entropy brain principle, in terms of increased brain entropy in relation to the psychedelic state (Carhart-Harris et al, 2014), and other flexible mental states such as Rapid Eyes Movement Sleep (Lee et al, 2013) and dreaming (Nardelli et al, 2019), jazz improvisation (Simon, 2005), and deep meditation (Kumar et al, 2022;Li, Hu, Zhang and Zhang, 2011) -and reduced brain entropy under states of reduced consciousness such as deep sleep (Kung et al, 2022), the anaesthetized state (Fuentes et al, 2022) and disorders of consciousness (Visani et al, 2022). More specific support for REBUS can be found in perceptual changes under psychedelics (Kaiser and Gold, 1973), altered beliefs under (Safron, 2020) and after psychedelics (McGovern et al, 2022;Timmermann et al, 2021) as well as other trait changes (Aday et al, 2021) as well as decreased top-down processing seen through such metrics as travelling waves (Alamia et al, 2020), dynamic causal modelling (Muthukumaraswamy et al, 2013), and transfer entropy (Wang, Chen and Chen, 2022;Vicente et al, 2011) reduced hierarchical organisation under psychedelics (Girn et al 2022) and the flattening of the brain's energy landscape under (Singleton et al 2021) and after (Daws et al 2022) psychedelics.…”

A Two-Stream Graph Convolutional Network Based on Brain Connectivity for Anesthetized States Analysis

“…Ketamine often causes complex, conscious experiences, which may result in an increase brain activity without abolishing consciousness [37,38]. Similar conclusions that ketamine increases neural activation and is associated with alterations of consciousness were reached in [39]. This is even in contrast with other anesthetics that act on the NMDA receptor like xenon, which reduces cortical activity in rat experiments [40].…”