EEG slow-wave coherence changes in propofol-induced general anesthesia: experiment and theory

Abstract

The electroencephalogram (EEG) patterns recorded during general anesthetic-induced coma are closely similar to those seen during slow-wave sleep, the deepest stage of natural sleep; both states show patterns dominated by large amplitude slow waves. Slow oscillations are believed to be important for memory consolidation during natural sleep. Tracking the emergence of slow-wave oscillations during transition to unconsciousness may help us to identify drug-induced alterations of the underlying brain state, and provide insight into the mechanisms of general anesthesia. Although cellular-based mechanisms have been proposed, the origin of the slow oscillation has not yet been unambiguously established. A recent theoretical study by Steyn-Ross et al. (2013) proposes that the slow oscillation is a network, rather than cellular phenomenon. Modeling anesthesia as a moderate reduction in gap-junction interneuronal coupling, they predict an unconscious state signposted by emergent low-frequency oscillations with chaotic dynamics in space and time. They suggest that anesthetic slow-waves arise from a competitive interaction between symmetry-breaking instabilities in space (Turing) and time (Hopf), modulated by gap-junction coupling strength. A significant prediction of their model is that EEG phase coherence will decrease as the cortex transits from Turing–Hopf balance (wake) to Hopf-dominated chaotic slow-waves (unconsciousness). Here, we investigate changes in phase coherence during induction of general anesthesia. After examining 128-channel EEG traces recorded from five volunteers undergoing propofol anesthesia, we report a significant drop in sub-delta band (0.05–1.5 Hz) slow-wave coherence between frontal, occipital, and frontal–occipital electrode pairs, with the most pronounced wake-vs.-unconscious coherence changes occurring at the frontal cortex.

Cortical functional connectivity indexes arousal state during sleep and anesthesia

“…2b). These observations under propofol are consistent with previous reports (Chennu et al, 2016; Feshchenko et al, 2004; Ni Mhuircheartaigh et al, 2013; Purdon et al, 2013; Supp et al, 2011; Tinker et al, 1977; Wang et al, 2014) and some have suggested that changes in frontal alpha and delta power are reliable indicators of loss of consciousness under propofol (Purdon et al, 2013). However, a recent study using the isolated forearm technique challenges the reliability of such an approach (Gaskell et al, 2017).…”

The value of intra-operative electrographic biomarkers for tailoring during epilepsy surgery: from group-level to patient-level analysis

“…This is a remarkable result considering the differences in methodological (and arbitrary) choices we used to harmonize the analysis pipelines of the aforementioned studies. For the biomarkers for which we failed to observe a significant effect (PLV and sdDTF) this failure could be indeed related to different signal processing pipelines regarding the epoch length 69 , the reference montage 70,71 , the different state of vigilance [72][73][74] .…”

Network Properties in Transitions of Consciousness during Propofol-induced Sedation

“…In this regard most studies of anaesthetic-induced changes in consciousness, infer this state from changes in behavioural responsiveness 1 , 2 . Reversible changes in consciousness, based on responsiveness, appear to correlate with changes in slow wave activity, measured by recording the power between 0.5 and 4 Hz (delta activity) 3 , 4 . In other words, it is well known the delta activity is a typical feature as a signature of unconsciousness 5 .…”