THE SCIENCE OF CONSCIOUSNESS
April 25-30, 2016 - Tucson, ARIZONA
Loews Ventana Canyon Resort
April 26, 2016
2:00 pm to 4:10 pm
PL 1 -Five Roads to Consciousness
Professor at the Collège de France, chair of Experimental Cognitive Psychology
Director of the INSERM-CEA Cognitive Neuroimaging Unit, NeuroSpin, Saclay, France
Stanislas Dehaene’s research combines the methods of experimental psychology, neuropsychology, neuroimaging and mathematical modeling in order to dissect the brain mechanisms of some major domains of human competence: mathematics, language processing, reading, and access to consciousness. Dehaene created simple yet innovative paradigms allowing those complex cognitive functions to be dissected under laboratory conditions, with a combination of behavioral and brain-imaging techniques.
His approach combines sophisticated behavioural paradigms with a variety of other experimental methods including neuropsychological studies of brain-lesioned patients and brain-imaging studies with positron emission tomography, functional magnetic resonance imaging, high-density recordings of event-related potentials, and intracranial recordings in epilepsy patients.
Born in 1965, Stanislas Dehaene was initially trained in mathematics and computer science. In 1984, he was admitted to the Ecole Normale Supérieure, rue d’Ulm in Paris, where he ranked 4th in the mathematics section. His interest was quickly aroused by the nascent domain of brain and cognitive sciences. In 1985, he joined the Laboratoire de Sciences Cognitives et Psycholinguistique (LSCP), founded and directed by Jacques Mehler. Dehaene started a PhD under Mehler’s direction, which he defended in 1989. Simultaneously, he started to collaborate with Jean-Pierre Changeux, Professor at Collège de France and head of a research unit at the Pasteur Institute in Paris, on the development of neuronal models of cognitive functions – a collaboration that continues to this day. In 1989, just prior to his PhD defense, he was granted a permanent research position at INSERM (Institut National de la Santé et de la Recherche Médicale, the French equivalent of NIH), where he spent most of this career. From 1992 to 1994, Dehaene stayed as a post-doc in Michael Posner’s laboratory at the University of Oregon, where he was first exposed to advanced brain-imaging techniques.
Taken together, Dehaene’s behavioral, neuropsychological, brain-imaging and modelling studies pointed to a precise prediction: in both human and non-human primates, there should be an evolutionary ancient neural code for number, a specific region of the cortex where individual neurons would be tuned to numerical quantities and show a Gaussian tuning curve on a compressive axis for number (Log-Gaussian tuning). The predicted neural code was subsequently demonstrated experimentally, at the expected intraparietal location, first in monkeys by Nieder and Miller, then in Dehaene’s laboratory using human fMRI.
In 1999, Dehaene received a centennial fellowship from the McDonnell Foundation to deepen his research on numerical abilities, their brain mechanisms and their pathologies. Dehaene demonstrated that the core number sense already exists in infants and in humans without access to education or symbols for number. He showed that impairments of the intraparietal area can be associated with developmental dyscalculia in a genetic disease, Turner’s syndrome. To help address these number-sense deficits, he developed two open-source adaptive software games for the remediation of arithmetic difficulties, the “Number Race” (www.thenumberrace.com) and the “Number Catcher” (www.thenumbercatcher.com), which are freely available on the internet and have now been translated in several languages.
Under the impulsion of Michael Posner and Bruce McCandliss, Dehaene extended the scope of his research to ask how education to cultural symbols such as written and spoken words impacts on brain development. He recently gave a demonstration of this approach by visualizing, with fMRI, the cerebral changes due to reading acquisition and absent from the brains of illiterate adults. The results supported his earlier identification, with Laurent Cohen, of the Visual Word Form Area (VWFA), a left occipito-temporal brain area that specializes for orthographic coding in literate subjects. Dehaene proposed a specific model of “local combination detectors” for the neural code in the visual word form area, and he performed a series of brain-imaging studies to test this hypothesis.
Already in the 1990’s, with Jacques Mehler, Laurent Cohen, Christophe Pallier and colleagues, Dehaene began to be interested in the brain networks for language. In 1993, they published one of the first systematic studies of syntax using positron emission tomography (PET). This was followed by a series of PET and fMRI studies of the localization, specialization and timing of spoken-language areas, both in the subject’s first language as well as in a second language learned later in life. Dehaene also collaborated with his spouse Ghislaine Dehaene-Lambertz, a neuro-pediatrician and cognitive psychologist specialized in infant cognition and brain development, who performed a landmark series of studies using infant brain-imaging to dissect the brain mechanisms of language acquisition. Those studies support Noam Chomsky’s concept of a specialized “language-acquisition device” by showing that the core language network is already active and hierarchically organized in 2-3 month-old infants, and quickly adapts to the specificities of the mother’s tongue.
In both arithmetic and language, Dehaene asked an original question: is cognitive processing possible without consciousness, or do certain steps require a conscious appraisal? Dehaene pioneered the use of brain imaging to investigate the subliminal processing of masked words and numbers. An influential and oft-replicated study, published in Nature (1998), demonstrated that an unseen number could activate a series of cortical representations and even influence motor decisions. By designing minimal contrasts between conscious and non-conscious experimental conditions, Dehaene probed the sequence of brain events leading to access to consciousness. Based on this empirical research, Dehaene and his PhD student Lionel Naccache developed a theory and, with Jean-Pierre Changeux, some computer simulations of a “global neuronal workspace”. The neurocognitive theory, founded upon an earlier psychological proposal by Bernard Baars, linked conscious access to the activation of a distributed set of parietal and prefrontal neurons with long axons. The theory led to the later discovery of a series of signatures of consciousness, i.e. markers derived from brain activity that reliably indicate whether a particular stimulus is consciously perceived, or whether a person is conscious. In 2010, Dehaene received a grant from the European Research Council (ERC) to pursue research on the brain mechanisms of consciousness. In collaboration with neurologist Lionel Naccache, he used his knowledge of the brain mechanisms of consciousness to develop fMRI and EEG tests which are now starting to be applied to brain-lesioned patients in coma, vegetative state, or minimal consciousness.
In 2005, the French Academy of Sciences recognized Stanislas Dehaene’s scientific contributions by electing him at an unusually young age. That same year, he was elected to a professorship at the Collège de France, on the newly created chair of Experimental Cognitive Psychology. He then became a member of the Pontifical Academy of Sciences (2008), a foreign associate of the US National Academy of Sciences (2010), a corresponding fellow of the British Academy (2010) and a member of the American Philosophical Society (2010). His research was distinguished by the Dr A.H. Heineken Prize for Cognitive Science (2010) and the Grete Lundbeck Brain Prize (2014, with G. Rizzolatti and T. Robbins).
Dehaene enjoys using those platforms to convey, to a broad audience, the most recent and exciting findings in cognitive neuroscience. He is particularly interested in developing the applications of psychological science to education, and has served on the advisory board of various institutions including the French Ministry of Education and the Organization for Economic Cooperation and Development (OECD). To share his passion for brain and cognitive sciences, Dehaene has written three general-audience books in cognitive science: "The number sense" (1997), "Reading in the brain" (2009), and “Consciousness and the brain” (2014).