Neural Correlates of Consciousness at Near-Electrocerebral Silence in an Asphyxial Cardiac Arrest Model

Abstract

Recent electrophysiological studies have suggested surges in electrical correlates of consciousness (i.e., elevated gamma power and connectivity) after cardiac arrest (CA). This study examines electrocorticogram (ECoG) activity and coherence of the dying brain during asphyxial CA. Male Wistar rats (n = 16) were induced with isoflurane anesthesia, which was washed out before asphyxial CA. Mean phase coherence and ECoG power were compared during different stages of the asphyxial period to assess potential neural correlates of consciousness. After asphyxia, the ECoG progressed through four distinct stages (asphyxial stages 1–4 [AS1-4]), including a transient period of near-electrocerebral silence lasting several seconds (AS3). Electrocerebral silence (AS4) occurred within 1 min of the start of asphyxia, and pulseless electrical activity followed the start of AS4 by 1–2 min. AS3 was linked to a significant increase in frontal coherence between the left and right motor cortices (p < 0.05), with no corresponding increase in ECoG power. AS3 was also associated with a significant posterior shift of ECoG power, favoring the visual cortices (p < 0.05). Although the ECoG during AS3 appears visually flat or silent when viewed with standard clinical settings, our study suggests that this period of transient near-electrocerebral silence contains distinctive neural activity. Specifically, the burst in frontal coherence and posterior shift of ECoG power that we find during this period immediately preceding CA may be a neural correlate of conscious processing.

Identifying neuronal correlates of dying and resuscitation in a model of reversible brain anoxia

“…In line with findings in human patients (Clute and Levy, 1990;Chawla et al, 2009;Pana et al, 2016) and in previous in vivo models of brain anoxia (Hansen, 1978;Vanderwolf et al, 1988;Silver and Erecinska, 1990;van Rijn et al, 2011;Borjigin et al, 2013;Kongara et al, 2014;Lee et al, 2017), we found that the interruption of oxygen supply led to a rapid (within 40─60 s) dissolution of ECoG signals, which was preceded by successive surges of fast and slow activities. The flattening of cortical signal was correlated with a decrease in the amplitude and frequency of synaptic potentials in the simultaneously recorded pyramidal neurons, consistent with the reduction of excitatory and inhibitory synaptic currents observed in neocortical cells after anoxia (Rosen and Morris, 1993;Peña and Ramirez, 2005).…”

“…For example, inducing an abrupt cardiac arrest in rats by intra-cardiac injection of potassium chloride led to a fast decline in EEG amplitude associated, within the first 30 s preceding the isoelectric line, with a surge of widespread high-frequency gamma oscillations (Borjigin et al, 2013). In another cardiac arrest rodent model, wherein anoxia was induced by an interruption of the artificial ventilation, the attenuation of EEG activity towards the isoelectric state was accompanied by a decreased power in all frequency bands and an increased functional connectivity between bilateral frontal cortices (Lee et al, 2017). Interruption of cerebral blood flow by decapitation in rats also resulted in a rapid loss of global EEG power, occasionally associated with slow waves or low amplitude fast activity (Vanderwolf et al, 1988;van Rijn et al, 2011;Kongara et al, 2014).…”

High-speed quantitative optical imaging of absolute metabolism in the rat cortex

“…Ten male Wistar rats (weight to 400 g) were imaged, and details of the animal preparation procedures are described in our previous publications. 8 , 12 , 15 , 16 Before the experiment, all subjects were endotracheally intubated under isoflurane anesthesia. Each subject had epidural screw electrodes implanted for electrocorticography (ECoG) and a hemicraniectomy (4 mm right-to-left × 6 mm anterior-to-posterior) was performed to enable imaging of a portion of the right sensory and visual cortices.…”

Spreading depolarization and repolarization during cardiac arrest as an ultra-early marker of neurological recovery in a preclinical model

“…The animal model of ACA and resuscitation employed in this study has been described previously [41][42][43][44]48 and is summarized in Fig. 1.…”