title: 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.
authors.affiliation: 1 Department of Neurology, University of California , Irvine, California.
authors.forename: Donald E
authors.initials: DE
authors.lastname: Lee
authors.affiliation: 1 Department of Neurology, University of California , Irvine, California.
authors.forename: Lauren G
authors.initials: LG
authors.lastname: Lee
authors.affiliation: 1 Department of Neurology, University of California , Irvine, California.
authors.forename: Danny
authors.initials: D
authors.lastname: Siu
authors.affiliation: 1 Department of Neurology, University of California , Irvine, California.
authors.forename: Afsheen K
authors.initials: AK
authors.lastname: Bazrafkan
authors.affiliation: 1 Department of Neurology, University of California , Irvine, California.
authors.forename: Maryam H
authors.initials: MH
authors.lastname: Farahabadi
authors.affiliation: 1 Department of Neurology, University of California , Irvine, California.
authors.forename: Tin J
authors.initials: TJ
authors.lastname: Dinh
authors.affiliation: 2 Center for the Neural Basis of Cognition, Carnegie Mellon University , Pittsburgh, Pennsylvania.
authors.forename: Josue
authors.initials: J
authors.lastname: Orellana
authors.affiliation: 3 Department of Neurology, Case Western Reserve University School of Medicine , Cleveland, Ohio.
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.affiliation: 4 Department of Biomedical Engineering, University of California , Irvine, California.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Lopour
authors.affiliation: 1 Department of Neurology, University of California , Irvine, California.
authors.forename: Yama
authors.initials: Y
authors.lastname: Akbari
mesh_terms: D000818:Animals; D001237:Asphyxia / Q000503:physiopathology; D001921:Brain / Q000503:physiopathology*; D003243:Consciousness / Q000502:physiology*; D004195:Disease Models, Animal; D004569:Electroencephalography; D006323:Heart Arrest / Q000503:physiopathology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
keywords: cardiac arrest; coherence; connectivity; consciousness; electroencephalogram; near death