Impaired thalamocortical connectivity in humans during general-anesthetic-induced unconsciousness.
Whereas converging lines of evidence suggest that anesthetic-induced unconsciousness may result from disruption of functional interactions within neural networks involving the thalamus and cerebral cortex, the effects anesthetics have on human thalamocortical connectivity remain unexamined with current neuroimaging techniques. To address this issue we retrospectively analyzed positron emission tomography data from 11 volunteers scanned for regional cerebral glucose utilization (rCMRglu) when awake and again during isoflurane- (n = 6) or halothane- (n = 5) induced unconsciousness using statistical parametric mapping (SPM99) and structural equation modeling. A main effect analysis, contrasting awake and unconscious metabolic activity, localized a discrete region of the left va/vl thalamus whose relative rCMRglu activity was significantly suppressed (P < 0.05, corrected) during the unconscious state. To identify brain regions whose functional connectivity with this region of the thalamus was impaired during the unconscious state, a psychophysiological interaction analysis was performed. This analysis revealed effects predominantly in topographically related areas of the primary motor and supplementary motor association cortices. Structural equation modeling of a neuroanatomical network encompassing these empirically identified regions revealed significant state-related changes in effective connectivity (chi(2)diff (6)-15.88; P < 0.05) which primarily involved impairment of thalamocortical and corticocortical projections during the unconscious state. These findings support the hypothesis that a mechanistic component underlying general-anesthetic-induced unconsciousness involves disruption of functional interactions within thalamocortical neural networks.
White
Nathan S
NS
Department of Anesthesiology, University of California at Irvine, Irvine, CA 92868, USA.
Alkire
Michael T
MT
D000768:Anesthesia, General; D001786:Blood Glucose / Q000378:metabolism; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000187:drug effects*; D003198:Computer Simulation; D004292:Dominance, Cerebral / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D019788:Fluorodeoxyglucose F18; D006221:Halothane; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007530:Isoflurane; D008279:Magnetic Resonance Imaging; D008432:Mathematical Computing; D009415:Nerve Net / Q000187:drug effects; D009434:Neural Pathways / Q000187:drug effects*; D012016:Reference Values; D012189:Retrospective Studies; D009435:Synaptic Transmission / Q000187:drug effects*; D013787:Thalamic Nuclei / Q000187:drug effects*; D014055:Tomography, Emission-Computed; D014474:Unconsciousness / Q000000981:diagnostic imaging*; D014851:Wakefulness / Q000502:physiology
D001786:Blood Glucose; D019788:Fluorodeoxyglucose F18; D007530:Isoflurane; D006221:Halothane