[A scientific model of consciousness: implications for neuropsychiatic diseases]

Consciousness is an essential property of human cognition. According to the "Global neuronal workspace" hypothesis designed by Dehaene et al., consciousness results from amplification and synchronisation of distant processors. Frontoparietal loops play a crucial role in this large scale synchronisation. At any given time, many modular cerebral networks are active in parallel and process information unconsciously. An information becomes conscious, however, if the neural population that represents it is mobilized by top-down attentional amplification into a brain-scale state of coherent activity. This long-distance connectivity makes the information available to a variety of processes including perceptual categorization, long-term memorization, evaluation, and intentional action. Behavioral as well as neuroimaging studies using masked subliminal perception support this theoretical view. Among neuropsychiatric disorders, many neuroscientific studies have been devoted to schizophrenia. Some of them conclude on a global brain disconnectivity rather than on specific and localised perturbations. Hence conscious integration may be the core deficit in cognitive disabilities observed in schizophrenia. As shown in recent results, threshold for access to consciousness in schizophrenic patients compared with controls is elevated whereas unconscious processes, such as the ones involved in subliminal priming remain effective. We conclude on the potential use of the "global neuronal workspace" model in other neuropsychiatric diseases such as Alzheimer's disease or multiple sclerosis.