Preserved feedforward but impaired top-down processes in the vegetative state |
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| Authors: | Boly Melanie Garrido Marta Isabel Gosseries Olivia Bruno Marie-Aurélie Boveroux Pierre Schnakers Caroline Massimini Marcello Litvak Vladimir Laureys Steven Friston Karl |
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| Institution: | Coma Science Group, Cyclotron Research Centre and Neurology Department, University of Liège and CHU Sart Tilman Hospital, 4000 Liège, Belgium. mboly@ulg.ac.be |
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| 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. |
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