Leonardo's Brain Page 5

  Michelangelo was twenty-five and Leonardo was forty-eight in 1500. The young sculptor had thrilled the citizens of Florence with his statue of David, completed when he was only twenty-one. Leonardo also had to compete with the even younger boy wonder, Raphael, the artist upon whom the authorities were lavishing rich commissions.

  Michelangelo intensely disliked Leonardo because Leonardo maintained that the art of painting was far superior to sculpture, and wrote disparagingly about what he considered to be a lesser art: “The sculptor’s face is so smeared with marble dust, he looks like a baker. The painter, by contrast, works at ease; he is well dressed; he moves a light brush dipped in delicate colors and adorns himself with the clothes he fancies.” Such comments did not endear Leonardo to the highly sensitive Michelangelo.

  Fortunately, Leonardo soon obtained a commission to paint the Holy Family, and began work on a revolutionary grouping of Mary’s mother Anne, Mary, and the baby Jesus. As was often the case, he never finished it. The fault, as in similar situations, was not entirely his. One of the most notorious and disreputable characters to live in a time that was filled with notorious and disreputable characters offered Leonardo a high-paying, prestigious job as his military adviser and chief engineer.

  Cesare Borgia was the son of Pope Alexander VI. Alexander had two infamous children: the ill-reputed Lucrezia Borgia and Cesare, a man noted for his exceptional cruelty. Alexander had appointed Cesare a cardinal when the teenager was seventeen, but his father soon accepted that his son was not cut out to be a man of the cloth. He released his son from his vows and instead appointed him the titular ruler of Romagna, a region along the Adriatic coast with ill-defined borders that encompassed the land south of Venice and around Ravenna. Significantly, the Pope had not bothered to inform the existing rulers of the city-states of Romagna that they were now under the hegemony of a Borgia. Thus, his decree set in motion a series of wars between the local populations, who resisted the invasion of a well-armed, well-financed Borgia usurper.

  It is another of the many paradoxes of Leonardo’s life that a man who called warfare una pazzia bestialissima (a most bestial folly) and detested violence would end up on the payroll of such an unscrupulous and violent person. It is a measure of how badly Leonardo needed the money and wanted to leave Florence that he took the position with Cesare Borgia.

  It was during his employ with Borgia that Leonardo focused his interest on cartography. Beginning with the exquisite jewel of a map that he drew of the town and surrounding countryside of Imola, he went on to create even more detailed maps of northern Italy, from higher and higher vantage points. No one has been able to adequately explain how Leonardo was able to envision the aerial maps of Italy from such staggering heights.

  An unforeseen result of Leonardo’s association with Cesare was a friendship with another of the Renaissance’s key thinkers. In 1502, Leonardo met and formed a lasting relationship with Niccolò Machiavelli, who had joined Cesare as a young administrator and liaison. The two men met at the court of Cesare Borgia in the town of Imola. Historians presume that Cesare Borgia was the model for Machiavelli when he wrote his classic, The Prince.

  While in the employ of Cesare, Leonardo and Machiavelli were approached by authorities of Florence who asked for their help in defeating their commercial rival, the city-state of Pisa. Leonardo devised a most outlandish engineering scheme: divert the Arno River away from Pisa and deprive the city-state of its lifeblood. An attractive side benefit of this was to dredge a series of canals that would make the Arno a navigable river that could accommodate seafaring vessels for Florence. Machiavelli convinced the city’s elders to fund this expensive project, but as so often happened with Leonardo’s plans, it was dogged by bad luck, underfunding, and the poor workmanship of those to whom he had delegated authority. The scheme failed despite the considerable time and resources that the rulers of Florence had devoted to it. Leonardo and Machiavelli made little mention of the project in their subsequent writings.

  Leonardo left the employ of Cesare Borgia after he learned that Cesare had personally strangled a subordinate that Leonardo had befriended. He returned once again to Florence. Michelangelo had also left, and was now working for the Signora of Florence. Florence had its two most famous artistic sons Leonardo and Michelangelo in one place. The governing body decided that they should paint two different battle scenes in which Florentine forces were victorious. Leonardo drew the commission to paint the Battle of Anghiari. All of the citizens took a keen interest in this competition, because it was widely known that the two artists disliked each other. The barely civil rivalry between Leonardo and Michelangelo soon became known as the “battle of the battles.”

  When Leonardo displayed his cartoon (a drawing to be used as a model for the final work), there was widespread amazement; as word spread, people arrived from afar to see it. Like so many of his other projects, fate was to interfere with its completion. Both the French king Louis XII and his son Francis I had instructed their aide, Charles d’Amboise, to order the Signora to release Leonardo from his obligations in Florence and send him to Milan to the court of the French immediately. At first, the Florentines were reluctant to allow Leonardo to leave, but the victorious French were in possession of a larger army, and that fact persuaded the Italians to submit. (Michelangelo never completed his commission, either, as he was called to Rome by Pope Julius II to paint the ceiling in the Sistine Chapel.) And so with another project unfinished, Leonardo packed his bags and headed back to Milan. One of the projects Leonardo took with him on his trek north was the portrait he was working on of a Florentine woman known only as La Gioconda (1504). She would later become the most famous painting in the history of art, known in English as the Mona Lisa [Fig. 1].

  Unlike Leonardo’s previous stay in Milan, his duties were light this time. He revisited a project that he had begun over twenty years earlier and painted a second version of Virgin of the Rocks (1506). His residence in Milan was short because an alliance of Venetians and Spaniards—with the help of papal armies—successfully drove the French out of Milan. Once again, Leonardo was forced to flee. And, once again, his situation was dire. He did not have a patron. He had little money. He had left a trail of unfinished works.

  News that Pope Julius II had suddenly died and the College of Cardinals had elected a Medici from Florence to be the next pope gave Leonardo hope that at last he could find work in Rome. Leo X, the new pope, let it be known that he intended to leave an artistic legacy in the city. Leonardo headed for Rome with high expectations that he could secure a few of the commissions that his fellow Florentine was promising to lavish.

  When he arrived, he found Michelangelo had finished his painting of the Sistine Chapel, and Raphael had painted his famous mural, The School of Athens. The architect Donato Bramante was occupied with the erection of St. Peter’s Basilica. Leonardo failed to land a lucrative commission. Another factor was that Leonardo was engrossed in human dissection at this time, and his work did not go unnoticed. Leonardo wrote in his notebooks, “An ill-wisher hindered me in anatomy, denouncing it before the Pope and also at the hospital.” This and other reports of his time spent with rotting corpses so displeased the Pope that it increasingly appeared Leonardo’s hopes for success in Rome would come to naught.

  Yet once again, fate intervened. The young French king Francis I had been so impressed with Leonardo when he’d spent time with him in Milan that he invited the aging master to come live with him in France and be his court artist.

  At Chambord, in the bucolic Loire River valley, Leonardo finally found peace. His duties were light, and he was given a chateau at Amboise. Now in his sixties, his health had begun to fail; according to Antonio de Beatis, the secretary to the cardinal, “Leonardo’s physical condition is that in 1517, his right hand was ‘paralyzed.’ ” Beatis goes on to say that this paralysis prevented him from painting.*

  * There is some dispute concerning which hand was paralyzed. Leonardo was left-handed, and he d
rew the elegant Turin red chalk self-portrait after this incident.

  The French king traveled regularly to visit Leonardo. When asked why he didn’t summon Leonardo to his court, the younger man replied that it was easier for him to travel to visit Leonardo than it was for the artist to make the trip to Paris. Leonardo spent the last few years of his life consumed as always with matters related to his boundless curiosity. He died in France in 1519 at the age of sixty-seven, and was buried at the Chapel of Saint-Hubert in Amboise.

  Chapter 4

  Mind/Brain

  Iron rusts from disuse; stagnant water loses its purity, and in cold weather becomes frozen; even so does inaction sap the vigour of the mind.

  —Leonardo da Vinci

  The theme of duality in human nature, of inner conflict, of man divided against himself has been at the core of great literature, art, and philosophy for thousands of years. Is the split-brain just another metaphor, or is there something deeper, something literal for us here?

  —David Galin, split-brain researcher

  Time and Space are Real Beings, a Male & a Female. Time is a Man, Space is a Woman.

  —William Blake

  To understand the uniqueness of Leonardo’s brain, we must first consider our own. The human brain remains among the last few stubborn redoubts to yield its secrets to the experimental method. During the period that scientists expanded the horizons of astronomy, balanced the valences of chemistry, and determined the forces of physics, the crowning glory of Homo sapiens and its most enigmatic emanation, human consciousness, resisted the scientific model’s persistent searching.

  The brain accounts for only 2 percent of the body’s volume, yet consumes 20 percent of the body’s energy. A pearly gray, gelatinous, three-pound universe, this exceptional organ can map parsecs and plot the whereabouts of distant galaxies measured in quintillions of light-years. The brain accomplishes this magic trick without ever having to leave its ensorcelled ovoid cranial shell. From minuscule-wattage electrical currents crisscrossing and ricocheting within its walls, the brain can reconstruct a detailed diorama of how it imagines the Earth appeared four billion years ago. It can generate poetry so achingly beautiful that readers weep, hatred so intense that otherwise rational people revel in the torture of others, and love so oceanic that entwined lovers lose the boundaries of their physical beings.

  Distinctly different from all other creatures, the human brain can use its powerful time awareness to range along a vector of past, present, and future that includes the “Big Bang” fourteen billion years ago. Despite the extraordinary intelligence of dogs, cats, seals, dolphins, elephants, and chimpanzees, there exists not a one among them that a human could train to keep an appointment to meet at a particular location two weeks hence. No other animal’s brain can hold steady in its consciousness the extended time frames from both the past and the future that a human can.

  Similarly remarkable is the bipedal primate’s freedom to explore space. All other complex animals remain tightly tethered by an invisible instinctual leash that confines them to a defined territory, flyway, or migration route. The human brain, in contrast, seems to possess an internal neuro-spatial GPS guidance system that allows its owner to wander freely all over the planet. While there exist a handful of creatures possessed of wanderlust, none can match a human in his or her willingness to explore distant and/or hostile environments. Moreover, no other creature has both plumbed the pressure-crushing depths of the oceans and escaped from the Earth’s atmosphere to voyage to the sublunary reaches of cold space.

  Early scientists, attempting to understand the human brain, confronted the ultimate “black box” problem: The investigative apparatus necessary to study the object of interest was the object itself.

  Modern neuroscience has its roots with ancients who began gleaning information about brain function by studying patients who had something going very wrong inside their cranium. But first, these early observers had to discard the erroneous belief that consciousness arose in the heart, not the brain. Given the virile vigor of the beating heart constantly rattling its cage when compared to the goopy brain, which to an untrained eye did not appear to do anything, one can easily forgive the earliest clinicians for making this error. Hippocrates, the Greek, fourth century BC father of all physicians, set the record straight. Using no device other than his own acumen, he correctly identified the conductor orchestrating consciousness as standing before a podium located behind the forehead rather than the breastplate.

  Unfortunately, the practice of autopsy was taboo in ancient times.* Not until the Renaissance did a few of the culture’s more intrepid explorers let their curiosity overcome squeamishness and religious strictures. Postmortems afforded a physician the opportunity to compare the clinical symptoms he observed during life with the lesions apparent in various parts of the brain after death.

  * Although there is evidence of trepanning (the boring of holes in the skull) among early cultures and the Egyptians certainly practiced postmortem examinations and removal of the internal organs, there is no evidence that any pre-Greek cultures had ever investigated what might be the function of the organs they were removing. From the available evidence, it appears that these activities were associated with magico-religious considerations more than scientific curiosity.

  This method had the inherent disadvantage of the interested party having to patiently await the subject’s demise before he could pry open the deceased’s skull to discover the physical abnormality lurking there. The clinician then would have to begin the difficult task of correlating the identified distinctive material defect observed within the brain with the neurologic deficit that he had noted during the patient’s life. Given the complexities of any single individual’s brain when added to the extreme variations between one brain and another, combining circumstantial observation with deductive reasoning was excruciatingly slow and hard work.

  Moreover, the brain decomposes rapidly after death, leaving a very short window during which any aspiring ancient pathologist could work. Even after fixative stains, formaldehyde, and microscopes upgraded the process from the primitive to the refined, hurdles persisted. Peering at postmortem tissue on a slide under a microscope or examining a formaldehyde-­fixed slice of dead brain tissue was a poor substitute for observing the living organ in real time, actively crackling with electrochemical jolts of energy and somersaulting neurotransmitters.

  Another erroneous conception about the brain impeded understanding of its operating system’s underlying architecture. The seventeenth-century philosopher René Descartes had authoritatively declared, “I observe . . . the brain to be double, just as we have two hands, two eyes, and two ears.” Descartes would not entertain the notion that the brain would be anything but elegantly designed so that each half was the exact mirror image of the other. A measure of how entrenched this idea had become can be found in the statement of the French physiologist Bichat, who wrote in 1800, “Harmony is to the function of organs as symmetry is to their configuration.” To Bichat and generations of earlier anatomists, because each half of the brain appeared symmetrical upon examination, it must follow that each side must function in a complementary way.

  Additionally Descartes concluded that the mind was something completely separate from the body. Its ethereal nature caused Descartes to place the mind in the world of immaterial spirit. He introduced to philosophy the mind/body split, and in so doing inadvertently distinguished the brain and its principal by-product—consciousness—as something completely “other” than the more prosaic interlocking body parts that went about their business grinding and meshing below the neck.

  God’s special organ within God’s special creation was essentially off limits to the more mundane human investigators. Descartes’ philosophical decapitation lingered until the mid-nineteenth century, when a breakthrough discovery exposed his fallacy. Paul Broca, a French physician, fractured the symmetry of this organ and in a single bold stroke initiated the beginning of modern
neurology. By connecting the common clinical syndrome of speechlessness (aphasia) that often followed a cerebral accident with its frequent accompaniment, paralysis of the right side of the body, he correctly located speech primarily in only one hemisphere of the brain; the majority of humans being right-handed, Broca identified the unique functions of the left hemisphere.* (Due to the arrangement of crisscrossed fibers in the brain, the left hemisphere controls the right side of the body and the right hemisphere controls the left side.) Soon afterward, Carl Wernicke further refined Broca’s observation by distinguishing another location in the left hemisphere that was specifically concerned with making sense of what we hear as opposed to Broca’s area further forward, whose primary purpose was generating intelligible speech. Broca’s and Wernicke’s discovery of dedicated areas of the brain performing specific language skills introduced a novel way to conceive of brain functions.

  * The French country physician Marc Dax had made this observation in the eighteenth century, but was unable to properly connect the defect of aphasia and paralysis of one side of the body with the localization of speech and preferential handedness to one dominant hemisphere.

  With the advent of the twentieth century, new investigative tools gave neuroscientists the ability to study the brains of normal people in real time. The first was the measurement of brain waves. Because neurons, the workhorse cells of the nervous system, operate by using electrochemical impulses, they generate weak electromagnetic fields that extend into the surrounding space. The cortex, just under the bony plates of the skull, contains the most concentrated mass of neurons in the brain, and the neurons’ combined activity can be measured by attaching sensors to a subject’s scalp. The readout occurring in real time is called an electroencephalogram, or EEG. Following rapidly on the heels of this breakthrough came other developments that provided neuroscientists with increasingly sophisticated tools to investigate elusive brain functions.