Stanislas Dehaene

Stanislas Dehaene is a disciple of Jean-Pierre Changeux. Changeux said that together they "sketched out a model - albeit a still very elemental one - of a neural network."

Dehaene was perhaps first known for his 1997 book The Number Sense, in which specific neurons were identified for numerical cognition. With colleagues he discovered lesions in regions of the parietal lobe that impaired multiplication but preserved subtraction and others (in the intraparietal sulcus) which impaired subtraction but preserved multiplication.

Later Dehaene worked on the neural correlates of consciousness,. He wrote many scientific articles and edited a book, The Cognitive Neuroscience of Consciousness.. He is the Past President of the Association for the Scientific Study of Consciousness.

He calls his theory of consciousness a "global neuronal workspace," an extension of Bernard Baars' Global Workspace Theory. He says the "proposal is simple: consciousness is brain-wide information sharing."

The human brain has developed efficient long-distance networks, particularly in the prefrontal cortex, to select relevant informa­tion and disseminate it throughout the brain. Consciousness is an evolved device that allows us to attend to a piece of information and keen it active within this broadcasting system. Once the information is conscious, it can be flexibly routed to other areas according to our current goals, we can name it, evaluate it, memorize it, or use it to plan the future. Computer simulations of neural networks show that the global neuronal workspace hypothesis generates precisely the signatures that we see in experimental brain recordings. It can also explain why vast amounts of knowledge remain inaccessible to our consciousness.
For Dehaene, the brain-wide information sharing is the result of what he calls "cortical ignition," and "brain-scale synchrony" of neuronal spikes and brain waves that are observable via electroencephalography (EEG).

Dehaene is correct that information is moving from place to place in the brain. But he is cautious. Questions remain. How can the "signatures of consciousness" that he measures result in "subjective experiences?"

Why should late neuronal firing, cortical ignition, and brain-scale synchrony ever create a subjective state of mind? How do these brain events, however complex, elicit a mental ex­perience? Why should the firing of neurons in brain area V4 elicit a perception of color, and those in area V5 a sense of motion? Although neuroscience has identified many empirical correspondences between brain activity and mental life, the conceptual chasm between brain and mind seems as broad as it ever was.
In our experience recorder and reproducer (ERR) model of the mind, consciousness is explained by the re-firing of multiple Hebbian assemblies, each one a complex of neurons that were originally wired together when a past experience was first recorded.

Donald Hebb said "neurons that fire together wire together." Information philosophy says that neurons that have been wired together in a past experience will all fire together again when even a small number of them fire during a new experience, thus bringing the past experience to mind.

Which pre-wired assemblies of neurons fire is determined (statistically) by the particular combination of sensory and limbic neurons that fire in the new experience. The Hebbian assemblies most likely to fire again are those with the most neurons in common with the new experience. In this we find a neuronal level explanation for the "association" of ideas as put forward by John Locke in his Essay Concerning Human Understanding (1690).

The reproduction or "playback" of a past experience may be a pale shadow of the original, as David Hume argued. And immense numbers of past experiences are likely to be reproduced (William James' "blooming buzzing confusion"), lessening the importance of any one. But together past experiences provide the "context" that gives "meaning" to the current experience.

An experience is "subjective" because it is contextualized, interpreted, and understood in the light of the unique past experiences of the individual.

While the neurons that fire together may be anywhere in the neocortex, those associated with a given experience are a tiny subset of them all, so particular experiential information is not simultaneously shared brain-wide, as Dehaene assumes.