Understanding how brain activity leads to a conscious experience remains a major experimental challenge. I will describe a series of experiments that probe the signatures of conscious processing. In these experiments, my colleagues and I ask whether a specific type of brain activity can be detected when a person suddenly becomes aware of a piece of information. We create minimal contrasts whereby the very same visual stimulus is sometimes undetected, and sometimes consciously seen. We then use time-resolved methods of electro- and magnetoencephalography to follow the time course of brain activity. The results show that conscious access relates to a global burst of late synchronized activity (a cortical “ignition”), distributed through many cortical areas. We propose a theory of a global neuronal workspace, according to which what we experience as a consciousness is the global availability of information in a large-scale network of pyramidal neurons with long-distance axons. This knowledge is now being applied to the monitoring of conscious states in non-communicating patients. Using real-time signal processing techniques, we believe that a few minutes of testing with simple sounds and two recording electrodes might suffice to determine whether a person is conscious.
Stanislas Dehaene (Collège de France & CEA)
Stanislas Dehaene is professor at the Collège de France, where he holds the chair of Experimental Cognitive Psychology. He directs the INSERM-CEA Cognitive Neuroimaging Unit at NeuroSpin in Saclay, south of Paris -- France’s advanced neuroimaging research center. His research investigates the neural bases of human cognitive functions such as reading, calculation and language, with a particular interest for the differences between conscious and non-conscious processing. His main research findings include the discovery of automatic links between numbers and space, and of the role of the intraparietal sulcus in number sense; the operation of the “visual word form area”, a left occipito-temporal region which acquires the visual component of reading; and the identification of physiological responses unique to conscious processing, supporting the theory of a “global neuronal workspace” for consciousness. He is the author of "The number sense" (1997/2010) and "Reading in the brain" (2009), and the editor of "The cognitive neuroscience of consciousness" (2001) and "From monkey brain to human brain" (2007). He is a member of the French and US Academies of Sciences and the Pontifical Academy of Sciences, and the recipient of the Dr. A.H. Heineken Prize in Cognitive Science (2009) and the McDonnell Centennial Award (1999).