Consciousness and the Brain according to Stanislas Dehaene

I have read many books and articles on this subject over the past 20 years; but, I must admit, this book by French neuroscientist Stanislas Dehaene (Viking, 2014) feels like he's geting a lot right. He does it through brain imaging and metaphoric language.

His main contention is that "a staggering amount of unconscious processing occurs beneath the surface of our conscious mind." Imaging methods have become so precise that they can now show exactly where global unconscious processing crosses over into conscious thought. Admittedly, David Eagleman has been saying the same thing in his popular PBS series, The Brain. What does pass into conscious thought, said in the French way, is la crème de la crème of what the unconscious proposes to the conscious mind. Further, as Eagleman has said too, what we sense is "not raw sensation, but an expert reconstruction of the outside world."

Here's a good metaphoric offering from Dehaene:

"Unsurprisingly, it turns out that our attentional spotlight is operated by armies of unconscious workers that silently sift through piles of rubble before one of them hits gold and alerts us of its finding."

In another metaphoric rendering, he says: "The fortress of the conscious mind possesses a small drawbridge that forces mental representations to compete with one another. Conscious access imposes a narrow bottleneck." The best thought breaks on through to the other side.

Unconscious processing explains how mathematicians and scientists suddenly get answers to tricky conundrums when stepping up on a bus or shaving; and how poets get a fully formed poem, seemingly from out of nowhere, when waking up in the morning or taking a walk in the afternoon. The unconscious miners have been sifting through the rubble all along and the drawbridge has been crossed.

If the hard work is going on beneath the hood, so to speak, what is consciousness for anyway?

Simply put, unconscious processing is fleeting and unstable, whereas consciousness pins it down. On top, in the prefrontal cortex, neurons can hold on to and manipulate at a later time thoughts that would otherwise be lost forever down in the basement. It is also the front of the brain that allows us to share information with others. As Dehaene says, "Imperfect as it is, our human ability for introspecting and social sharing has created alphabets, cathedrals, jet planes and lobster Thermidor." With his penchant for poetry, Dehaene cites Julian Jaynes's definition of consciousness as "a secret theater of speechless monologue and prevenient counsel, an invisible mansion of all moods, musings, and mysteries, an infinite resort of disappointments and discoveries."

Further, consciousness has a "tipping point." In an "avalanche" of neuronal activity, another Dehaene metaphor, "the frontal regions of the brain are being informed of sensory inputs in a bottom-up manner, but these regions also send massive projections in the converse direction, top-down, and to many distributed areas." The end result is a brain web of synchronized areas. Only activation of the prefrontal cortex (top) and the parietal cortex (bottom) in long-distant loops creates conscious experience.

But that's not all. With all this activity going on, some neuronal firing has to be pared down to let the essentials through. A conscious idea is encoded by small patches of active and synchronized cells, together with a massive crown of inhibited neurons--a positive electrical potential--called the P3 wave on the surface of the head. Dehaene theorizes that the brain is highly self-stimulating, creating its own neuronal activity all the time, even when we are asleep. In the absence of external stimulation, the brain generates its own, as we saw in Oliver Sacks's Hallucinations.

Having worked with babies, along with his wife who is a neuropediatrician, Dehaene has concluded that babies are most likely conscious at birth, but their developing minds work much more slowly than ours. Even at two months old, they are already processing language in Broca's area in the left hemisphere and show evidence of remembering. Yes, he uses fMRIs designed especially for babies.

Dehaene made the interesting discovery that the amygdala, which lies at the bottom of the temporal lobe, responds to fearful words flashed to it, even without the person's conscious awareness. This unconscious processing of an invisible word remains in the left temporal lobe, only becoming conscious when it invades the frontal lobes. Of course, since he does not introduce the notion of atypical lateralization, I must add that the light bulb over the head effect might be occurring over the right side of the brain for some.

Here is a Dehaenian formula worth repeating: "My theory is that the architecture of the conscious workspace plays an essential role in facilitating the exchange of information among brain areas. Thus, consciousness is a useful device that is likely to have emerged a long time ago in evolution and perhaps more than once." Further, he says that the workspace system "may well be present in all mammals" and possibly in birds and fish as well. However, "[i]n humans alone, the power of this communication device was later boosted by a second evolution: the emergence of a 'language of thought; that allows us to formulate sophisticated beliefs and to share them with others."

Finally, Dehaene explains schizophrenia as a breakdown in the top-down processing of neural information. With their long-distance neural connections impaired, schizophrenics would feel that "something remains to be explained, that the world contains many hidden layers of meaning, deep levels of explanation that only they can perceive and compute. As a result, they would continually concoct far-fetched interpretations of their surroundings." As the top-down prediction system fails, as sense impressions become strange, "it is a short step to becoming convinced that you hear voices in your head."

Leonardo's Brain and Leonard Shlain

Like most people writing about the brain, Shlain (2014) focused first on a “universal model” which recognizes the primacy of the left hemisphere for language, linearity and logic while the right indulges in emotionality, poetry, creative artistry and humor. With his dual scientific and artistic genius, Leonardo did not fit the “typical” dominance mold. Shlain proposed that Leonardo’s brain was bilaterally organized, with neither side favored over the other. With this cerebral balance, Leonardo could be both an “extraordinary left-brained academician obsessed with portraying perspective correctly and an impish right-brained trickster who takes delight in fooling the viewer with perspectivist sleights of hand (7).” Leonardo, per Shlain, excelled in both science and art thanks to a large corpus callossum with more than typical neurons connecting the left and right hemispheres.      

      I was initially pleased that Shlain wrote about Leonardo’s childhood traumas because it fit my own paradigm of the creative poetic mind. Leonardo was the illegitimate child of a peasant girl and a rich city boy. His mother, whose marriage to another man had been arranged by Leonardo’s father’s family, raised him in the countryside. But, when Leonardo’s biological father married a 16-year-old girl, he moved his now 5-year-old son back into his own household, separating him from his biological mother. The new stepmother died in childbirth. Leonardo’s father married three more times, producing ten more children. This all sounds highly traumatic, but Leonardo would be well raised by his grandparents and his uncle Francesco (Capra: 66).

       When Leonardo’s grandfather died and Francesco married, even these losses led to a significant gain for the now 12 year old. Leonardo left the farm for the beautiful, artistic city of Florence with his father. He began an apprenticeship with an important artist and craftsman, a friend of his father’s, several years later. According to Fritjof Capra (2007), this intellectual and creative environment “shaped” Leonardo’s “entire approach to art and science (73).” He had at his disposal all the equipment and materials he needed for his many inventions in this workshop. In a later move to Milan, he was given a large workspace to fulfill his artistic duties to the court and do research on his burgeoning scientific and mathematical interests, especially geometry, along with access to the large and important library at the University of Pavia.

      Leonardo led a seemingly charmed life. He was considered by one and all to be physically beautiful; a flamboyant dresser; loving, eloquent and charming; an athlete; an excellent horseman; a musician, and serenely self-confident (Capra: 18-21). Nonetheless, at the societal level, his illegitimacy barred him from attending university; he did not begin learning Latin, necessary for reading most scholarly works, until he was 40 years old. This very constraint may have impelled his insatiable scientific inquiries through direct observation and his need for perfection in his art. We should also recall that he was a product of his times. Being a “Renaissance” man required knowing everything then, as it does now.

      Yet, an underlying difference in Leonardo’s brain lateralization cannot be denied. Shlain (2014) quotes Leonardo’s Treatise on Painting (1651), which advised artists how to “quicken the spirit of invention”:

• You should look at certain walls strained with damp, or at stones of uneven colour. If you have to invent some backgrounds you will be able to see in these the likeness of divine landscapes, adorned with mountains, ruins, rocks, woods, great plains, hills and valleys in great variety; and expressions of faces and clothes and an infinity of things which you will be able to reduce to their complete and proper forms. In such walls the same thing happens as in the sound of bells, in whose stroke you may find every named word which you can imagine (61).

While possibly good advice, it tells us more about the extent of Leonardo’s own active imagination and his ability to convert environmental sights and sounds into a new vision or voice, transformed from a stain on a wall or heard in clanging bells. Leonardo’s advice notwithstanding, this is not a universal skill. Rather, it is more likely encountered in altered states of consciousness, from whatever the source—sleep deprivation, isolation, drug usage, or organic injury to the brain, such as epilepsy or head trauma. A left-hander’s bilaterally organized brain, with an enhanced right hemisphere, could make associative visual or auditory connections that typical minds could not.[1]

      Shlain was one of the first writers to accent the left versus right hemispheric differences in creativity, based on important theorists of the 1980’s. I agree with him that myths derive from left-hemispheric confabulated stories trying to make sense of anomalous right-hemispheric voices and visions. Shlain says,

• Although each hemisphere has its own preferences and approaches, each contributes to make a whole person only when the corpus callosum integrates the two. But in the process of generating a major creative insight, a disconnect must occur between the two halves. Arthur Koestler called this the ‘hemispheric bisociation’ (91-92) . . . [Koestler also described the act of creation as “thinking aside” and it was clear to him that there could be no truth without beauty, whether artistic, mathematical, or scientific. If you look closely at the tattered cover of my 1989 edition of Koestler's classic, you'll see that the figure is tossing about pages of Leonardo's drawings, a poem, and musical notes. [These were the days when cover art was beautifully enigmatic, not diagrammatic or technological.]

Still describing the typical mind, Shlain says the “the right brain is essentially bereft of language, the description in words of how the creative process proceeds is practically impossible. Ask artists or scientists how they arrived at their most novel and creative work, and you will no doubt receive either an inarticulate answer or the left brain’s confabulation (98-9).” He does not postulate that language can be dominant on the right or spread out in both hemispheres.

      Beyond his reliance on science mostly from the 1980’s, Shlain comes to this odd conclusion about creativity:

• Creativity is at its base a combination of fear and lust. Danger and sex are the fundamental processes that artists traditionally call upon to create a work of art. Of course, he or she is not aware that these are the root causes. Creativity begins with perceiving a pattern, a feature, or an alternative use for a common object.[2] After recognizing something novel, the artist breaks down the observation into its component parts. This is primarily a left-brained function, reductionist and analytic. An artist will reassemble the pieces into a new and compelling manner that others will recognize as art. But the work of art must contain ‘passion.’ It must be a work of ‘love.’ He or she must be in a nearly ‘orgasmic’ state to produce it. Our word enthusiasm comes form Dionysian enthousiasmos, a wild state of holy inspiration. Orgasm is a right-hemispheric function. Love is rooted in the right brain. Ecstasy is an emotion experienced at the right of the corpus callosum (100-101).”

     Pursuing Leonardo’s cerebral differences, Shlain explains that the anterior commissure, which connects the temporal lobes, can be as much as 30 percent larger in women than men, 15% larger in gay men than straight men and larger still in both left-handed men and women. Most authors agree that Leonardo was left-handed and possibly gay, so he would indeed have had a more bilateral brain. Fritjof Capra (2007) says the artist was ambidextrous, able to write equally well with both hands.

      What about the mirror handwriting? Some authors agree that Leonardo wrote backwards so as not to smear the ink (Shlain; Nathan and Zöllner). Shlain adds that “[l]eft-handers must employ hook handwriting to avoid this distressing trait when they write from left to right (173).” Again, as a left-hander, and with confirmation from others on my blog post “The Eye of the Beholder,” I know that all left-handers do not hook their hand when writing. It depends on whether they are left or right dominant for language (President Clinton does not hook his hand. President Obama does). If indeed Leonardo’s mirror writing was designed to avoid smearing the ink, it would put his language function more squarely in the left hemisphere, reserving the right for visuo-spatial processing. The fact that he drew facial profiles to the right and his background hatching ran top left to bottom right shows a left-hander at work (Nathan and Zöllner: 137, 196). 

His impressive maps were in part drawn on Ptolemy’s Geographia, but he was also a mountaineer. His aerial views may well have been part visionary, part actual, part imaginary, like so much of his work (image below in Nathan and Zöllner: 484-5). Shlain suggests that Leonardo practiced remote viewing to get these views on paper. I will not discount the possibility of non-local perception, given the extent of Leonardo’s bilateral dominance, with enhanced right-hemispheric functioning.

   Shlain recognized that Leonardo’s language was highly metaphorical and that poetry is right-hemispheric language, as professor and poet Julie Kane has explained. Shlain’s conclusion, specifically with regard to the Renaissance artist, is well put, but requires refinement: “Leonardo had all the characteristics of the brain that would allow for an increased sensibility to aesthetics, harmony, and creativity. They were present as the result of differences in the organization of the possibly gay, left-hander’s, musical, backward-writing, ambidextrous brain (175).”

      While I am indebted to Shlain for the biographical details on Leonardo da Vinci’s early life, and agree in principle with the bilateral thesis, we need a fuller picture to understand the artist’s mind and practices. Capra, for instance, says Leonardo’s notes for his drawings were not only written backwards, they were “disjointed,” using “highly idiosyncratic” spelling and syntax, no spaces between words, and virtually no punctuation other than periods. It is quite possible that he was dyslexic, with compensatory visual prowess, or, possibly, that he was merely in a rush to get the words down, while perfecting his images, over and over again. Leonardo himself asserted that drawings were much important than words and painting more important than poetry (Capra: 39, 143).      
     Leonardo also did more drawings than paintings when usually the reverse is true for artists (Nathan and Zöllner: 12). An enormous percentage of his works has been lost and no studies remain for the Mona Lisa (Nathan and Zöllner: 16). What is especially interesting to me is his visuo-spatial capacity. Rather than drawing from a model, he was often drawing on memory alone and actually sought out certain faces on the street to be captured on paper only after returning to his study.  

     The fact that Leonardo never systematized his scientific work, according to Capra, shows him to be deliberately secretive, making it more difficult for others to steal his ideas. He even "designed his study so that the platform holding his work could be lowered through the floor to the story below . . . to hide it from inquisitive eyes whenever he was not working (Capra: 27)." Critical transcriptions that do exist to decipher Leonardo’s mirror writing, which has proven to be "highly eloquent, often witty, and at times movingly beautiful and poetic (Capra: 166-8)," suggest a right-hemispheric provenance for language.

      Even Leonardo’s study of science sounds right hemispheric, because his focus was on patterns, not logical sequences. The Dyslexic Society claims many artists and inventors among their ranks, including Leonardo. Capra (2007) realized that:

• Leonardo’s systematic studies of living and nonliving forms amounted to a science of quality and wholeness that was fundamentally different from the mechanistic science of Galileo and Newton. At the core of his investigations, it seemed to me, was a persistent exploration of patterns, interconnecting phenomena from a vast range of fields (Capra: xviii).

     Capra cited an exhibit of Leonardo’s drawings at the Hayward Gallery in London, which summarized the master’s art as "part of a vision embracing a profound sense of the interrelatedness of things (Capra: xix)." I see it as analogical thinking (right-oriented) at its height, combined with an unprecedented attention to detail and an obsessive need to depict the real, as it actually is (left-oriented), as well as moving through time and space (non-local). Science and art were synthesized, even synchronized, showing whole brain simultaneous processing. Leonardo also had a prodigious memory, capable of holding enormous amounts of visual information in mind before committing it to paper or canvas, which, complementing his insatiable, intellectual curiosity, provided the intuitive means and the practical skill to get whatever he saw right, with a minimal use of words.

      Leonardo never accepted blindly the words in classical texts; rather, he did his own experiments and directly observed nature to decide for himself (Capra: 156). As to art, he could do both linear perspective drawings with mathematical precision and hyperrealistic human and animal drawings, the former left hemispheric and the latter, right hemispheric, in my opinion. His art was scientific and his science artistic, accenting one side or the other at will, depending on the eyes’ focus and the mind’s intent. Leonardo’s vision, thought processes and memory were so keen that intuition, a form of cognition for him, permitted him to make inventive leaps centuries ahead of his time.

      Mind must have a body and a brain, so Leonardo did not believe in disembodied spirits or an afterlife. But he did believe in the importance of the mother, beautifully expressed in this passage from his notebook that accompanied his splendid drawing of the fetus in the womb:

• One and the same soul governs these two bodies; and the desires, fears, and pains are common to this creature as to all other animated parts. . . . The soul of the mother . . . in due time awakens the soul which is to be its inhabitant. This at first remains asleep under the guardianship of the soul of the mother who nourishes and vivifies it through the umbilical vein (in Capra: 254). 
  

      
Capra says succinctly: "Never again . . . was so much intellectual and artistic genius embodied in a single human being (259)." Leonardo apparently agreed, acknowledging about himself:

 Read me, O reader; if in my words you find delight,

 For rarely in the world will one such as I be born again.

Capra, Fritjof. 2007. The Science of Leonardo: Inside the Mind of  
    the Great Genius of the Renaissance. New York: Doubleday.
Kane, Julie. 2004. "Poetry As Right-Hemispheric 
     Language."Journal of Consciousness Studies, 11 (5-6): 21-59.
Koestler, Arthur. 1964/1989. The Act of Creation. London and New      York: Arkana.
Nathan, Johannes and Zöllner, Frank. 2014. Leonardo da Vinci 
      1452-1519: The Graphic Work. Cologne: Taschen.
Shlain, Leonard. 2014. Leonardo's Brain: Understanding Da 
      Vinci's Creative Genius. Guilford, CT and Helena, MT: Lyons
      Press.

---

[1] As a left-handed, right-dominant person myself, I can provide a telling example. I once made a journey from the US to France with a long layover in London. Not having slept the entire night in Heathrow Airport, I boarded a small plane bound for Toulouse and immediately fell asleep. In that moment, I saw a static hypnagogic image of a ship crossing the English Channel with a crusader standing at the helm, white tunic and bright red cross gleaming. After arriving in Toulouse, and driving with my son to my destination on unfamiliar roads, I fell again into a fitful sleep. In the morning, I awoke to frightening images of “monkey men” projected onto the rough-hewn walls of the medieval stone house where I was staying.

[2] This is a common scientific study method, which, I consider unsuitable for judging artistic creativity.