It is now well established that, even during wakefulness, an important part of the stimulations we receive through our senses is processed non consciously, i.e. we do not have conscious access to them and, if prompted, we report that we have not seen them or heard them etc… This raises the following question: what brain mechanisms distinguish conscious from non-conscious processing ? We will present results in experimental psychology and neuroimaging in humans suggesting that conscious processing might be associated with the all-or none triggering of a specific form of brain-scale activity beyond the initial phase of sensory processing. We will present recent developments in trying to model these dynamics, in order to better describe and understand them. Being able to diagnose these dynamics could lead to interesting applications, notably informing the diagnosis of patients with disorders of consciousness.