See Also: Book Notes, (me), Notes on Consciousness, Social Conquest of Earth, Righteous Mind, Happiness Hypothesis, Consciousness: Confessions, Blank Slate, Info Viz & Perception, On Intelligence, The Quest for Consciousness, The Stuff of Thought, Neuroscience of Human Relationships, Human: Makes Us Unique, Thinking, Fast and Slow, Meca Loop

Consciousness and the Brain:

Deciphering How the Brain Codes Our Thoughts

Stanislas Dehaene (2014) Viking ISBN-13: 978-0670025435 - 266 pages text, 18 notes, 32 pages of references, 14 pages of index. (pronounced de HAH na)

This first thing I really like - and is new to me - is Dahaene's avenue of investigation about consciousness: measuring brain activity in response to subliminal stimuli and then measuring as stimuli is gradually increased until they become conscious phenomena to the subjects. For the first 1/3 of a second, there is little difference in the brain processing between what will stay subconscious and just fade away versus what will come to our attention. When the flood of visual/auditory sensations trigger an avalanche. The difference is that the supraliminal stimuli cause a global ignition, in which a much larger network of neurons light up. The frontal cortex is sending message back to the visual cortex to guide in the refinement of what we see. This larger coalition is the global neuronal workspace. Once in the Global Workspace, it is available to all other brain regions so they can take appropriate action - or be primed.

Also new, the concept of the Rider "sampling" the Elephant. System 1, aka, the elephant is presenting all sorts of information the the Rider/System2, and the Rider takes snapshots. See quote from p.97 below. I gotta believe this where the "see what you want see" action or inaction happens.

Chapter 2 is a well written catalog of all of the subconscious processing that is is the Elephant in Haidt's The Elephant And The Rider Metaphor and the System 1 in Kahneman's Thinking Fast and Slow. See the diagram further down the page. Great quote from Poincare:
"The subliminal self is in no way inferior to the conscious self; it is not purely automatic; it is capable of discernment; it has tact, delicacy; it knows how to choose, to divine. What do I say? It knows better how to divine than the conscious self, since it succeeds where that has failed. In a word, is not the subliminal self superior to the conscious self?"

p. 47 - "Recent experiments in psychology and brain imaging have tracked the fate of unconscious pictures in the brain. We recognize and categorize masked images unconsciously and we even decipher and interpret unseen words. Subliminal pictures trigger motivations and rewards in us all without our awareness. Even complex operations linking perception to action can unfold covertly, demonstrating how frequently we rely on an unconscious "automatic pilot." Oblivious to this boiling hodgepodge of unconscious processes, we constantly overestimate the power of our consciousness in making decisions-but in truth, our capacity for conscious control is limited.

More buzzwords: Attentional Blink, Psychological Refractory Period

image ignition.png

Signatures of Consciousness

Signatures of Consciousness form an upgrade from correlates of consciousness found in Christof Koch's The Quest for Consciousness. I would not say these are really signatures of consciousness, but rather signatures that new stimuli have entered consciousness - have made it into the Global Workspace. We retain whatever is conscious without the constant refresh of these signatures. Here are the . . .

p. 159 - "four reliable signatures of consciousness - physiological markers that index whether the participant experienced a conscious percept.
First, a conscious stimulus causes an intense neuronal activation that leads to a sudden ignition of parietal and prefrontal circuits.
Second, in the EEG, conscious access is accompanied by a slow wave called the P3 wave, which emerges as late as one-third of a second after the stimulus.
Third, conscious ignition also triggers a late and sudden burst of high-frequency oscillations.
Finally, many regions exchange bidirectional and synchronized messages over long distances in the cortex, thus forming a global brain web.

An avalanche is also used as a metaphor for ignition. The subliminal rumble of neural activity is almost identical to the supraliminal. Just a little bit strong stimulus triggers and avalanche that gets a new precept into the Global Workspace.

The P300 wave is much stronger in the case of ignition. It can be from 250ms to 500ms after the stimulus. The P3 wave is fired by the winning coalition, mostly to inhibit rival coalitions (p.179).

p.179 - "The landscape of active and inactive neurons can explain our second signature of consciousness: the P3 wave that I described in Chapter 4 a large positive voltage that peaks at the top of the scalp. During conscious perception, a small subset of workspace neurons becomes active and defines the current content of our thoughts, while the rest are inhibited. The active neurons broadcast their message throughout the cortex by sending spikes down their long axons. At most places, however, these signals land on inhibitory neurons. They act as a silencer that hushes entire groups of neurons: "Please remain silent, your features are irrelevant." A conscious idea is encoded by small patches of active and synchronized cells, together with a massive crown of inhibited neurons.

image workspace.png

Global Neuronal Workspace

This is an evolution of Baars's Global Workspace. I think the most concise description is in the introduction to Chapter 5:
p.161. In this chapter, I introduce the "global neuronal workspace" hypothesis, my laboratory's fifteen-year effort to make sense of consciousness. 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 keep it active within this broadcasting system. Once the information is conscious, it can be flexibly routed to other areas according to our current goals. Thus 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.

p.177 "higher sectors of the cortex" . . . "are particularly predominant in the prefrontal cortex but also in other sectors of the anterior temporal lobe, inferior parietal lobe, and a midline region called the precuneus. All send and receive numerous projections to and from a broad variety of distant brain regions, allowing the neurons there to integrate information over space and time. Multiple sensory modules can therefore converge onto a single coherent interpretation ("a seductive Italian woman"). This global interpretation may, in turn, be broadcast back to the areas from which the sensory signals originally arose. The outcome is an integrated whole. Because of neurons with long-distance top-down axons, projecting back from the prefrontal cortex and its associated high-level network of areas onto the lower-level sensory areas, global broadcasting creates the conditions for the emergence of a single state of consciousness, at once differentiated and integrated.

Altho the Global Workspace is much more explicitly defined by Dehaene, Christof Koch has the same notions as one of his 10 working assumptions in The Quest for Consciousness: 3) Conscious precepts are the results of a single winning coalition of neurons with at some prefrontal parts of the network.

image BrainRegionsIgnition.jpg

What Is Consciousness Good For?

p.96 (ambiguous images) - "Fascinatingly, the convergence process that leads our neurons to agree on a single interpretation vanishes under anesthesia. The loss of consciousness is accompanied by a sudden dysfunction of the neuronal circuits that integrate our senses into a single coherent whole. Consciousness is needed for neurons to exchange signals in both bottom-up and top-down directions until they agree with one another. In its absence, the perceptual inference process stops short of generating a single coherent interpretation of the outside world."

p.97 - "What we see at any time, tends to be the most likely interpretation, but, other possibilities occasionally pop up and stay in our conscious vision for a time duration that is proportional to their statistical likelihood. Our unconscious perception works out all of the probabilities - and then our consciousness samples from them at random."

p.102/103 - "In human subjects, memory-trace learning seems to occur if and only if the person reports being aware of the systematic predictive link between the tone and the air puff. Elderly people, amnesiacs and people who were simply too distracted to notice the temporal relationship show no conditioning at all (whereas these manipulations have no effect whatsoever on coincidence-based conditioning). Brain imaging shows that the subjects who gain awareness are precisely those who activate their prefrontal cortex and hippocampus during the learning." [ memory-trace learning means the air puff follows the tone by some amount of time. Like Pavlov's dog]

p.109 - multicore - " This active social transmission of a conscious symbol offers new computational abilities. Humans can create "multicore" social algorithms that do not draw solely on the knowledge available to a single mind but rather allow the confrontation of multiple points of view, variable levels of expertise, and a diversity of sources of knowledge."

p.110 - "Sharing information with others is a second reason our brain finds it advantageous to abstract from the details of our present sensations and create a conscious "brief." Words and gestures provide us with only a slow communication channel-only 40 to 60 bits per second,42 or about 300 times slower than the (now antiquated) 14,400-baud faxes that revolutionized our offices in the 1990s. Hence our brain drastically com- presses the information to a condensed set of symbols that are assembled into short strings, which are then sent over the social network. It would actually be pointless to transmit to others a precise mental image of what I see from my own point of view; what others want is not a detailed description of the world as I see it, but a summary of the aspects that are likely to also be true from my interlocutor's viewpoint: a multisensory, viewer-invariant, and durable synthesis of the environment."

image Chapter2elephant

More Notes

p.118 - "The primary visual cortex and surrounding areas were basically activated by all of the images, regardless of the amount of masking. In the higher visual centers of the cortex, however, within the fusiform gyrus and the lateral occipitotemporal region, a tight correlation urged between brain activation and reports of conscious reports.

p.126 - "the brain contains exquisite mechanisms that compensate for these delays . . .

p.135 - "The bestiary of brain oscillations includes the alpha band (8 to 13 hertz), the beta band (13 to 30 hertz), and the gamma band (30 hertz and higher) [jch - hertz is per second. 8 hertz means a pulse every 1/8 second]

p.244 - great discussion about consciousness in animals. For most definitions of consciousness, they are. DUH!!!

p.252 ". . . in humans the prefrontal cortex is vastly expanded ... Neurons have the largest dendritic trees ... Frontopolar cortex, or Brodmann's area 10 is larger in humans and the underlying white matter, the long distance axons to support connections to other regions, is disproportionate larger ...
. . . "Another special region is Broca's area, the left inferior frontal region that plays a critical role in human language. Its layer-3 neurons, which send long-distance projections, are more broadly spaced in humans than in other apes, again permitting a greater interconnection.49 In this area, as well as in the midline anterior cingulate, another crucial region for self-control, Constantin von Economo discovered giant [spindle] neurons that may well be unique to the brains of humans and great apes such as chimps and bonobos, as they seem to be absent in other primates, such as macaques.50 With their giant cell bodies and long axons, these cells probably make a very significant contribution to the broadcasting of conscious messages in the human brain."


One thing that was a little frustrating is that the Global Neuronal Workspace seemed to be used as if it were a specific thing, as if it were a workbench and you bring things to the workspace and they become conscious.

Also a bit frustrating is the use of the term code. The concept of a brain code - in the subtitle of the book! - was never developed. There was talk about how many different combinations of neuron connections there could be and that perhaps each concept or thing we have in our minds has a particular coalition of neurons to represent it.

And speaking of code and computers, I find it amusing to have on the same page, a little rant on how inadequate computers are followed by how great the global neuronal workspace simulator is.

Dahaene spends a lot of time talking about the ignition of consciousness and not a lot about the idling - the keeping those 7 +/- 2 things in mind.

For some context of how this work fits in read Christof Koch's take on the book in Scientific American Mind.

The Reality Club/ feedback from 2009

The two criticism in 2009 are addressed in the book. 300 ms - just to enter conscious ness. To keep it is easy. Default network is always active.

Could this be a better description of the Global Neuronal Workspace?

Check this out! -> Anil Seth (2007) Models of consciousness. Scholarpedia, 2(1):1328. P.S. I wonder if there is a first lieutenant coalition of neurons that runs the autopilot mindless tasks, like driving my car home along my commute.