title: Differential effects of deep sedation with propofol on the specific and nonspecific thalamocortical systems: a functional magnetic resonance imaging study.
abstract: BACKGROUND
  The current state of knowledge suggests that disruption of neuronal information integration may be a common mechanism of anesthetic-induced unconsciousness. A neural system critical for information integration is the thalamocortical system whose specific and nonspecific divisions may play the roles for representing and integrating information, respectively. How anesthetics affect the function of these systems individually is not completely understood. The authors studied the effect of propofol on thalamocortical functional connectivity in the specific and nonspecific systems, using functional magnetic resonance imaging.
  
  
  METHODS
  Eight healthy volunteers were instructed to listen to and encode 40 English words during wakeful baseline, light sedation, deep sedation, and recovery in the scanner. Functional connectivity was determined as the temporal correlation of blood oxygen level-dependent signals with seed regions defined within the specific and nonspecific thalamic nuclei.
  
  
  RESULTS
  Thalamocortical connectivity at baseline was dominantly medial and bilateral frontal and temporal for the specific system, and medial frontal and medial parietal for the nonspecific system. During deep sedation, propofol reduced functional connectivity by 43% (specific) and 79% (nonspecific), a significantly greater reduction in the nonspecific than in the specific system and in the left hemisphere than in the right. Upon regaining consciousness, functional connectivity increased by 58% (specific) and 123% (nonspecific) during recovery, exceeding their values at baseline.
  
  
  CONCLUSIONS
  Propofol conferred differential changes in functional connectivity of the specific and nonspecific thalamocortical systems, particularly in left hemisphere, consistent with the verbal nature of stimuli and task. The changes in nonspecific thalamocortical connectivity may correlate with the loss and return of consciousness.
authors.affiliation: Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Liu
authors.forename: Kathryn K
authors.initials: KK
authors.lastname: Lauer
authors.forename: B Douglas
authors.initials: BD
authors.lastname: Ward
authors.forename: Shi-Jiang
authors.initials: SJ
authors.lastname: Li
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Hudetz
mesh_terms: D000328:Adult; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects; D054810:Deep Sedation / Q000379:methods*; D017352:Echo-Planar Imaging / Q000379:methods; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009415:Nerve Net / Q000187:drug effects; D009434:Neural Pathways / Q000187:drug effects; D015742:Propofol / Q000494:pharmacology*; D012016:Reference Values; D013787:Thalamic Nuclei / Q000187:drug effects*; D014851:Wakefulness; D055815:Young Adult
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol