title: Preserved covert cognition in noncommunicative patients with severe brain injury?
abstract: BACKGROUND
  Despite recent evidence suggesting that some severely brain-injured patients retain some capacity for top-down processing (covert cognition), the degree of sparing is unknown.
  
  
  OBJECTIVE
  Top-down attentional processing was assessed in patients in minimally conscious (MCS) and vegetative states (VS) using an active event-related potential (ERP) paradigm.
  
  
  METHODS
  A total of 26 patients were included (38 ± 12 years old, 9 traumatic, 21 patients >1 year postonset): 8 MCS+, 8 MCS-, and 10 VS patients. There were 14 healthy controls (30 ± 8 years old). The ERP paradigm included (1) a passive condition and (2) an active condition, wherein the participant was instructed to voluntarily focus attention on his/her own name. In each condition, the participant's own name was presented 100 times (ie, 4 blocks of 25 stimuli).
  
  
  RESULTS
  In 5 MCS+ patients as well as in 3 MCS- patients and 1 VS patient, an enhanced P3 amplitude was observed in the active versus passive condition. Relative to controls, patients showed a response that was (1) widely distributed over frontoparietal areas and (2) not present in all blocks (3 of 4). In patients with covert cognition, the amplitude of the response was lower in frontocentral electrodes compared with controls but did not differ from that in the MCS+ group.
  
  
  CONCLUSIONS
  The results indicate that volitional top-down attention is impaired in patients with covert cognition. Further investigation is crucially needed to better understand top-down cognitive functioning in this population because this may help refine brain-computer interface-based communication strategies.
authors.affiliation: University Hospital of Liège, Liège, Belgium University of Liège, Liège, Belgium c.schnakers@gmail.com.
authors.forename: Caroline
authors.initials: C
authors.lastname: Schnakers
authors.affiliation: Spaulding Rehabilitation Hospital and Harvard Medical School, Boston, MA, USA JFK Johnson Rehabilitation Institute, Edison, NJ, USA.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Giacino
authors.affiliation: Sunnaas Rehabilitation Hospital, Nesoddtangen, Norway University of Oslo, Oslo, Norway.
authors.forename: Marianne
authors.initials: M
authors.lastname: Løvstad
authors.affiliation: University Hospital of Liège, Liège, Belgium University of Liège, Liège, Belgium.
authors.forename: Dina
authors.initials: D
authors.lastname: Habbal
authors.affiliation: University Hospital of Liège, Liège, Belgium University of Liège, Liège, Belgium.
authors.forename: Melanie
authors.initials: M
authors.lastname: Boly
authors.affiliation: Hangzhou Normal University, Hangzhou, China.
authors.forename: Haibo
authors.initials: H
authors.lastname: Di
authors.affiliation: University of Liège, Liège, Belgium.
authors.forename: Steve
authors.initials: S
authors.lastname: Majerus
authors.affiliation: University Hospital of Liège, Liège, Belgium University of Liège, Liège, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Laureys
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology; D001921:Brain / Q000503:physiopathology*; D001930:Brain Injuries / Q000150:complications / Q000503:physiopathology*; D003071:Cognition / Q000502:physiology*; D004569:Electroencephalography; D018913:Event-Related Potentials, P300; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018458:Persistent Vegetative State / Q000209:etiology / Q000503:physiopathology*
keywords: attention; consciousness; event-related potentials; minimally conscious state; vegetative state