Signatures of conscious processing in the human brain
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1
InsermCEA Cognitive Neuroimaging Unit, CEA/SAC/DSV/DRM/NeuroSpin, France
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, and multivariate decoding techniques to extract the activity profiles that encode conscious or unconscious information.
The results show that conscious access relates to a global burst of late synchronized activity (a cortical “ignition”), distributed through many cortical areas, and with strong inter-areal communication across distant cortical sites. They fit with the 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 linked by long-distance axons.
This knowledge is now being applied to the monitoring of conscious states in non-communicating patients. By combining event-related and EEG-based measures of cortical activation, local fluctuations and global long-distance synchrony, we can reliably begin to sort out patients in coma, vegetative state or minimal consciousness.
References
Dehaene, S., & Changeux, J. P. (2011). Experimental and theoretical approaches to conscious processing. Neuron, 70, 200-227.
Keywords:
Consciousness,
Magnetoencephalography,
EEG/ERP,
masking,
vegetative state,
Coma,
MMN (Mismatch negativity)
Conference:
Belgian Brain Council, Liège, Belgium, 27 Oct - 27 Oct, 2012.
Presentation Type:
Oral Presentation (only for invited speakers)
Topic:
Higher Brain Functions in health and disease: cognition and memory
Citation:
Dehaene
S
(2012). Signatures of conscious processing in the human brain.
Conference Abstract:
Belgian Brain Council.
doi: 10.3389/conf.fnhum.2012.210.00132
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Received:
20 Jul 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Dr. Stanislas Dehaene, InsermCEA Cognitive Neuroimaging Unit, CEA/SAC/DSV/DRM/NeuroSpin, GIF/YVETTE, F-91191, France, Stanislas.Dehaene@cea.fr