title: Repertoire of mesoscopic cortical activity is not reduced during anesthesia.
abstract: Consciousness has been linked to the repertoire of brain states at various spatiotemporal scales. Anesthesia is thought to modify consciousness by altering information integration in cortical and thalamocortical circuits. At a mesoscopic scale, neuronal populations in the cortex form synchronized ensembles whose characteristics are presumably state-dependent but this has not been rigorously tested. In this study, spontaneous neuronal activity was recorded with 64-contact microelectrode arrays in primary visual cortex of chronically instrumented, unrestrained rats under stepwise decreasing levels of desflurane anesthesia (8%, 6%, 4%, and 2% inhaled concentrations) and wakefulness (0% concentration). Negative phases of the local field potentials formed compact, spatially contiguous activity patterns (CAPs) that were not due to chance. The number of CAPs was 120% higher in wakefulness and deep anesthesia associated with burst-suppression than at intermediate levels of consciousness. The frequency distribution of CAP sizes followed a power-law with slope -1.5 in relatively deep anesthesia (8-6%) but deviated from that at the lighter levels. Temporal variance and entropy of CAP sizes were lowest in wakefulness (76% and 24% lower at 0% than at 8% desflurane, respectively) but changed little during recovery of consciousness. CAPs categorized by K-means clustering were conserved at all anesthesia levels and wakefulness, although their proportion changed in a state-dependent manner. These observations yield new knowledge about the dynamic landscape of ongoing population activity in sensory cortex at graded levels of anesthesia. The repertoire of population activity and self-organized criticality at the mesoscopic scale do not appear to contribute to anesthetic suppression of consciousness, which may instead depend on large-scale effects, more subtle dynamic properties, or changes outside of primary sensory cortex.
authors.affiliation: Department of Anesthesiology, Center for Consciousness Science, Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, United States. Electronic address: ahudetz@med.umich.edu.
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Hudetz
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States.
authors.forename: Jeannette A
authors.initials: JA
authors.lastname: Vizuete
authors.affiliation: Department of Psychiatry, University of Wisconsin-Madison, Madison, WI, United States.
authors.forename: Siveshigan
authors.initials: S
authors.lastname: Pillay
authors.affiliation: Department of Anesthesiology, Center for Consciousness Science, Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, United States.
authors.forename: George A
authors.initials: GA
authors.lastname: Mashour
mesh_terms: D000758:Anesthesia; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D003243:Consciousness / Q000187:drug effects / Q000502:physiology; D000077335:Desflurane; D004305:Dose-Response Relationship, Drug; D004567:Electrodes, Implanted; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D017207:Rats, Sprague-Dawley; D012815:Signal Processing, Computer-Assisted; D014793:Visual Cortex / Q000187:drug effects* / Q000502:physiology*; D014851:Wakefulness / Q000187:drug effects / Q000502:physiology
chemical_list: D018685:Anesthetics, Inhalation; D000077335:Desflurane; D007530:Isoflurane
keywords: anesthesia; avalanche; consciousness; criticality; information integration; synchrony