[en] Background. Despite recent evidence suggesting that some severely brain-injured patients retain some capacity for topdown
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.
Conclusion. 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.
Research center :
Centre, University of Liège and University Hospital of Liège, Sart Tilman,
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