Periodic Reporting for period 1 - CONSCIOUSBRAIN (Brain mechanisms of conscious processing, from correlates to signatures)
Reporting period: 2023-01-01 to 2025-06-30
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.
Two years into the project, the different branches have advanced satisfactorily. We have achieved, with fMRI, a characterization of the brain networks associated with task-related versus task-free conscious processing of auditory stimuli around threshold (see Figure 1). These data are corroborated by intracranial recordings with the same protocol, that allow analyzing neural activity at a finer scale. We have tested a first version of this protocol in electroencephalography with patients with disorders of consciousness, which already allows distinguishing different groups of patients depending on whether they show or not late sustained activity. We have designed an improved version of this protocol that should be even more sensitive in detecting task-free conscious access and hence should allow making individual diagnosis in these patients. We will also use it to probe conscious access and its dissolution in sleep and anesthesia.
We are currently analyzing a first set of magnetoencephalographic data which disentangles preconscious sensory processing from conscious access in a visual protocol. At the same time, we are working on building an improved version of this protocol.
We started applying models inspired from system dynamics in physics to characterize the brain dynamics we observed in our protocols. We are also working on a major update of the global workspace model that will describe the mechanisms of conscious access beyond task-related processes.
We are currently analyzing a first set of magnetoencephalographic data which disentangles preconscious sensory processing from conscious access in a visual protocol. At the same time, we are working on building an improved version of this protocol.
We started applying models inspired from system dynamics in physics to characterize the brain dynamics we observed in our protocols. We are also working on a major update of the global workspace model that will describe the mechanisms of conscious access beyond task-related processes.
The fMRI and intracranial results represent significant advances beyond the state-of-the-art, as they provide clear evidence of the existence of what we call a “global playground” during task-free conscious processing, namely the idea that, even when no decision making is taking place, conscious access involves a dialog between sensory areas and higher-level areas, notably in the frontal cortex (Figure 1). These are particularly hot topics in the domain nowadays, therefore this work has the potential to constitute an important breakthrough.
The update to the global neuronal workspace model should also constitute an important landmark. Indeed, this model is one of the main current models in the field, but its main weakness is that it only considers conscious access in the context of performing a task. Our update overcomes this limitation and reveals the full potential of the central ideas of the global workspace, namely the importance of broadcasting local information globally to allow conscious processing.
The update to the global neuronal workspace model should also constitute an important landmark. Indeed, this model is one of the main current models in the field, but its main weakness is that it only considers conscious access in the context of performing a task. Our update overcomes this limitation and reveals the full potential of the central ideas of the global workspace, namely the importance of broadcasting local information globally to allow conscious processing.