title: Default network connectivity reflects the level of consciousness in non-communicative brain-damaged patients.
abstract: The 'default network' is defined as a set of areas, encompassing posterior-cingulate/precuneus, anterior cingulate/mesiofrontal cortex and temporo-parietal junctions, that show more activity at rest than during attention-demanding tasks. Recent studies have shown that it is possible to reliably identify this network in the absence of any task, by resting state functional magnetic resonance imaging connectivity analyses in healthy volunteers. However, the functional significance of these spontaneous brain activity fluctuations remains unclear. The aim of this study was to test if the integrity of this resting-state connectivity pattern in the default network would differ in different pathological alterations of consciousness. Fourteen non-communicative brain-damaged patients and 14 healthy controls participated in the study. Connectivity was investigated using probabilistic independent component analysis, and an automated template-matching component selection approach. Connectivity in all default network areas was found to be negatively correlated with the degree of clinical consciousness impairment, ranging from healthy controls and locked-in syndrome to minimally conscious, vegetative then coma patients. Furthermore, precuneus connectivity was found to be significantly stronger in minimally conscious patients as compared with unconscious patients. Locked-in syndrome patient's default network connectivity was not significantly different from controls. Our results show that default network connectivity is decreased in severely brain-damaged patients, in proportion to their degree of consciousness impairment. Future prospective studies in a larger patient population are needed in order to evaluate the prognostic value of the presented methodology.
authors.affiliation: Coma Science Group, Cyclotron Research Centre, University of Liège, Allée du 6 août, B30, Liège, Belgium.
authors.forename: Audrey
authors.initials: A
authors.lastname: Vanhaudenhuyse
authors.forename: Quentin
authors.initials: Q
authors.lastname: Noirhomme
authors.forename: Luaba J-F
authors.initials: LJ
authors.lastname: Tshibanda
authors.forename: Marie-Aurelie
authors.initials: MA
authors.lastname: Bruno
authors.forename: Pierre
authors.initials: P
authors.lastname: Boveroux
authors.forename: Caroline
authors.initials: C
authors.lastname: Schnakers
authors.forename: Andrea
authors.initials: A
authors.lastname: Soddu
authors.forename: Vincent
authors.initials: V
authors.lastname: Perlbarg
authors.forename: Didier
authors.initials: D
authors.lastname: Ledoux
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Brichant
authors.forename: Gustave
authors.initials: G
authors.lastname: Moonen
authors.forename: Pierre
authors.initials: P
authors.lastname: Maquet
authors.forename: Michael D
authors.initials: MD
authors.lastname: Greicius
authors.forename: Steven
authors.initials: S
authors.lastname: Laureys
authors.forename: Melanie
authors.initials: M
authors.lastname: Boly
mesh_terms: D000328:Adult; D000368:Aged; D001930:Brain Injuries / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D003128:Coma / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D003243:Consciousness / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000502:physiology*; D018458:Persistent Vegetative State / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D011782:Quadriplegia / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology