Even during wakefulness, our brain processes a large amount of information unconsciously. For example, some visual information can enter our eyes and be processed by the brain without us having the conscious experience of seeing the stimulus. So, what is the difference in our brain when the same information is processed unconsciously versus consciously? By contrasting brain activity when people report having perceived a stimulus versus not, past research has revealed a general picture of all the neural activity that can correlate with conscious access. The great challenge we are currently facing is to identify, among all these correlates, what belongs to the core mechanism of conscious access, and distinguish them from preconscious sensory processing on the one hand, and from consequences of conscious access such as decision making, on the other hand. This is the objective of the present project. We designed novel protocols that allow desynchronizing the moment of conscious access from the initial sensory processing of a stimulus; we use them to disentangle neural signatures of conscious access from sensory precursors. We also discovered that conscious access seems to be associated with bifurcation dynamics: the same stimulus, when presented at the consciousness threshold, sometimes triggers late sustained activity, and sometimes not at all. These dynamics allow us to read out conscious access directly from the brain activity, irrespective of task-related processes or decision making. This experimental work will go hand in hand with an updating of one of the main current models of consciousness, the global workspace model. This research should help us achieve a better understanding of the core mechanism of conscious access. We will also use this knowledge to help diagnose conscious processing in patients with disorders of consciousness.
