title: Preserved feedforward but impaired top-down processes in the vegetative state.
abstract: Frontoparietal cortex is involved in the explicit processing (awareness) of stimuli. Frontoparietal activation has also been found in studies of subliminal stimulus processing. We hypothesized that an impairment of top-down processes, involved in recurrent neuronal message-passing and the generation of long-latency electrophysiological responses, might provide a more reliable correlate of consciousness in severely brain-damaged patients, than frontoparietal responses. We measured effective connectivity during a mismatch negativity paradigm and found that the only significant difference between patients in a vegetative state and controls was an impairment of backward connectivity from frontal to temporal cortices. This result emphasizes the importance of top-down projections in recurrent processing that involve high-order associative cortices for conscious perception.
authors.affiliation: Coma Science Group, Cyclotron Research Centre and Neurology Department, University of Liège and CHU Sart Tilman Hospital, 4000 Liège, Belgium. mboly@ulg.ac.be
authors.forename: Melanie
authors.initials: M
authors.lastname: Boly
authors.forename: Marta Isabel
authors.initials: MI
authors.lastname: Garrido
authors.forename: Olivia
authors.initials: O
authors.lastname: Gosseries
authors.forename: Marie-Aurélie
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: Marcello
authors.initials: M
authors.lastname: Massimini
authors.forename: Vladimir
authors.initials: V
authors.lastname: Litvak
authors.forename: Steven
authors.initials: S
authors.lastname: Laureys
authors.forename: Karl
authors.initials: K
authors.lastname: Friston
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001307:Auditory Perception; D001364:Awareness; D001499:Bayes Theorem; D001931:Brain Mapping; D003243:Consciousness; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory; D005260:Female; D005625:Frontal Lobe / Q000502:physiology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D015233:Models, Statistical; D009434:Neural Pathways; D010296:Parietal Lobe / Q000502:physiology / Q000503:physiopathology*; D018458:Persistent Vegetative State / Q000175:diagnosis / Q000503:physiopathology*; D011930:Reaction Time; D013702:Temporal Lobe / Q000502:physiology / Q000503:physiopathology*; D055815:Young Adult