Preserved feedforward but impaired top-down processes in the vegetative state.
Melanie Boly, Marta Isabel Garrido, Olivia Gosseries, Marie-Aurélie Bruno, Pierre Boveroux, Caroline Schnakers, Marcello Massimini, Vladimir Litvak, Steven Laureys, Karl Friston
Science (New York, N.Y.) May 13, 2011 DOI: 10.1126/science.1202043 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Population | Patients in a vegetative state and healthy controls |
| Key findings | The only significant difference between patients in a vegetative state and controls was an impairment of backward connectivity from frontal to temporal cortices, emphasizing the importance of top-down projections in recurrent processing for conscious perception. |
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.