title: Global reduction of information exchange during anesthetic-induced unconsciousness.
abstract: During anesthetic-induced unconsciousness (AIU), the brain undergoes a dramatic change in its capacity to exchange information between regions. However, the spatial distribution of information exchange loss/gain across the entire brain remains elusive. In the present study, we acquired and analyzed resting-state functional magnetic resonance imaging (rsfMRI) data in rats during wakefulness and graded levels of consciousness induced by incrementally increasing the concentration of isoflurane. We found that, regardless of spatial scale, the functional connectivity (FC) change (i.e., ∆FC) was proportionally dependent on the FC strength at the awake state across all connections. This dependency became stronger at higher doses of isoflurane. In addition, the relative FC change at each anesthetized condition (i.e., ∆FC normalized to the corresponding FC strength at the awake state) was exclusively negative across the whole brain, indicating a global loss of meaningful information exchange between brain regions during AIU. To further support this notion, we showed that during unconsciousness, the entropy of rsfMRI signal increased to a value comparable to random noise while the mutual information decreased appreciably. Importantly, consistent results were obtained when unconsciousness was induced by dexmedetomidine, an anesthetic agent with a distinct molecular action than isoflurane. This result indicates that the observed global reduction in information exchange may be agent invariant. Taken together, these findings provide compelling neuroimaging evidence suggesting that the brain undergoes a widespread disruption in the exchange of meaningful information during AIU and that this phenomenon may represent a common system-level neural mechanism of AIU.
authors.affiliation: The Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Hamilton
authors.affiliation: Department of Biomedical Engineering, The Pennsylvania State University, W-341 Millennium Science Complex, University Park, PA, 16802, USA.
authors.forename: Yuncong
authors.initials: Y
authors.lastname: Ma
authors.affiliation: The Huck Institutes of Life Sciences, The Pennsylvania State University, University Park, PA, 16802, USA. nuz2@psu.edu.|Department of Biomedical Engineering, The Pennsylvania State University, W-341 Millennium Science Complex, University Park, PA, 16802, USA. nuz2@psu.edu.
authors.forename: Nanyin
authors.identifier: http://orcid.org/0000-0002-5824-9058
authors.initials: N
authors.lastname: Zhang
mesh_terms: D018685:Anesthetics, Inhalation / Q000633:toxicity*; D000818:Animals; D020927:Dexmedetomidine / Q000633:toxicity; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D007091:Image Processing, Computer-Assisted; D007530:Isoflurane / Q000633:toxicity*; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D051381:Rats; D020318:Rats, Long-Evans; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D012146:Rest; D014474:Unconsciousness / Q000139:chemically induced* / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000503:physiopathology
chemical_list: D018685:Anesthetics, Inhalation; D020927:Dexmedetomidine; D007530:Isoflurane; D010100:Oxygen
keywords: Anesthetic-induced unconsciousness; Dexmedetomidine; Isoflurane; Rat; Resting-state functional connectivity