title: Persistent default-mode network connectivity during light sedation.
abstract: The default-mode network (DMN) is a set of specific brain regions whose activity, predominant in the resting-state, is attenuated during cognitively demanding, externally-cued tasks. The cognitive correlates of this network have proven difficult to interrogate, but one hypothesis is that regions in the network process episodic memories and semantic knowledge integral to internally-generated mental activity. Here, we compare default-mode functional connectivity in the same group of subjects during rest and conscious sedation with midazolam, a state characterized by anterograde amnesia and a reduced level of consciousness. Although the DMN showed functional connectivity during both rest and conscious sedation, a direct comparison found that there was significantly reduced functional connectivity in the posterior cingulate cortex during conscious sedation. These results confirm that low-frequency oscillations in the DMN persist and remain highly correlated even at reduced levels of consciousness. We hypothesize that focal reductions in DMN connectivity, as shown here in the posterior cingulate cortex, may represent a stable correlate of reduced consciousness.
authors.affiliation: Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California 94305-5235, USA. greicius@stanford.edu
authors.forename: Michael D
authors.initials: MD
authors.lastname: Greicius
authors.forename: Vesa
authors.initials: V
authors.lastname: Kiviniemi
authors.forename: Osmo
authors.initials: O
authors.lastname: Tervonen
authors.forename: Vilho
authors.initials: V
authors.lastname: Vainionpää
authors.forename: Seppo
authors.initials: S
authors.lastname: Alahuhta
authors.forename: Allan L
authors.initials: AL
authors.lastname: Reiss
authors.forename: Vinod
authors.initials: V
authors.lastname: Menon
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D016292:Procedural Sedation; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008874:Midazolam / Q000494:pharmacology; D009415:Nerve Net / Q000502:physiology*; D012146:Rest / Q000502:physiology*
chemical_list: D006993:Hypnotics and Sedatives; D008874:Midazolam