Great Myths of the Brain

Christian Jarrett

• Publisher: Wiley-Blackwell
• Year: 2014
• Print ISBN: 9781118312711, 9781118624500
• eBook ISBN: 9781118312704
• Edition: 1
• Topic: Psychology
• Subtopic: Cognitive Psychology & Cognition
• Index: Psychology

Great Myths of the Brain introduces readers to the field of neuroscience by examining popular myths about the human brain.

 

• Explores commonly-held myths of the brain through the lens of scientific research, backing up claims with studies and other evidence from the literature
• Looks at enduring myths such as "Do we only use 10% of our brain?", "Pregnant women lose their mind", "Right-brained people are more creative" and many more.
• Delves into myths relating to specific brain disorders, including epilepsy, autism, dementia, and others
• Written engagingly and accessibly for students and lay readers alike, providing a unique introduction to the study of the brain
• Teaches readers how to spot neuro hype and neuro-nonsense claims in the media

 

 

1
Defunct Myths

The consensus used to be that the earth is flat. Combustible materials, eminent scientists once proposed, all contain the nonexistent substance phlogiston. Mars, they told us, is crisscrossed with canals. All these once-influential ideas have been consigned to the scrap heap of obsolete theories. Brain science too has its share of defunct notions. This chapter is about those brain myths that no one (or very few people) believes any more. We'll start with the ancient idea that the mind is located, not in the brain, but in the heart. As the importance of the brain was eventually accepted, other myths to emerge or persist were that the nerves are filled with animal spirits and the main mental functions are located in the fluid-filled hollows of the brain: the ventricles.

Myth #1 Thought Resides in the Heart

It seems obvious to us today that thoughts and reason are located in the brain. That's because we've grown up knowing this universally accepted fact. But from a subjective point of view, there's little, other than the position of our eyes, to tell us that our mental life is housed in our heads. So perhaps we shouldn't be too surprised that many ancient civilizations from the Greeks to the Egyptians believed that the seat of mental function was located not in the brain but in the heart.

It is not that these cultures were necessarily unaware of the functional significance of the brain. Extracts from the Edwin Smith Surgical Papyrus (bought by the American archaeologist Edwin Smith in Luxor in 1862 and dated to approximately the age of the Pyramids) show us that the Ancient Egyptians recognized the potential effects of brain injury, including paralysis. But despite this knowledge, the cardiocentric view persisted, and the brain was seen as little more than a kind of bone marrow (today, the word for brain in many languages, including Russian “мозг,” Maori “roro,” Indonesian “benak,” Persian “

” and Swahili “ubongo” means literally “marrow”). Ancient Egyptian practices regarding the burial of the dead are revealing. Although the heart and other organs were venerated after death, left in the body for burial or preserved in canopic jars, the brain was scooped out via the nostrils, or a hole drilled in the base of the skull, and simply discarded.

In Ancient Greece, the Homeric poems from the eighth century bc reveal a belief in there being three types of soul – the psyche (a life-soul that animates the body), the thymos (associated with emotions), and the noos (associated with reason and intellect). The noos and thymos were both located in the chest, although not specifically in the heart. Among the first scholars to identify the heart specifically as involved in thought was Empedocles of Acragas (circa 495–435 bc) who believed that blood around the heart produced thoughts.

Perhaps the best-known cardiocentric advocate was Aristotle (384–322 bc). Like many others he was swayed by the fact that life ended when the heart stopped beating. Aristotle also noted how the brain was cold, senseless and peripheral whereas the heart was warm and central; that the heart develops in embryos before the brain; and that it is connected to all the sense organs whereas the brain is not (or so he mistakenly thought). Aristotle further reasoned that the brain couldn't be the control center for movement and sensation because invertebrates don't have brains.¹

Although he didn't see the brain as the seat of thought, Aristotle saw it as an important organ – he believed it was a bloodless, cooling radiator for the heart and that it was also involved in sleep. Another notable cardiocentrist was the physician Diocles of Carystus (circa fourth century bc) who made great breakthroughs in heart anatomy. Unfortunately, he interpreted his discoveries in line with his belief in the heart as a cognitive center, and so he saw the ear-like auricles of the heart as sense organs. Madness, he believed, is caused by the blood boiling in the heart (echoes of this idea remain today, as in “you make my blood boil”), and melancholy by the thickening of black bile, also in the heart.²

The cardiocentric view had actually been challenged decades before Aristotle by the philosopher-physician Alcmaeon of Croton (circa 450 bc), and later by Hippocrates, the “Father of medicine” (born circa 460 bc), and his followers. Alcmaeon was among the first scientists to perform animal dissections. Although his writings have been lost, quotations by others tell us that he wrote: “The seat of sensations is in the brain … it [is] also the seat of thought.” In a paper published in 2007, the neurobiologist Robert Doty at the University of Rochester argued that Alcmaeon's revelation was so profound as to be comparable in historical significance to the discoveries of Copernicus and Darwin.³

Also long before Aristotle, the Hippocratic treatise On The Sacred Disease (circa 425 bc) states: “Men ought to know that from the brain and the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears” and it goes on to attribute thinking and perceiving to the brain too. Another prescient Hippocratric treatise, On Injuries of the Head, states correctly that damage to one side of the brain causes impairments to the opposite side of the body.

After Hippocrates, further important breakthroughs were achieved by the Alexandrian anatomists, who were the first to perform systematic human dissections. Active around 300 bc, Herophilus of Chalcedon, often considered the founder of human anatomy, studied some of the cranial nerves and the ventricles (the fluid-filled hollows in the brain), while Erasistratus of Ceos compared the human cerebellum (the cauliflower-shaped “little brain” that hangs off the back of the brain) with the equivalent structure found in animals, deducing correctly that it must have something to do with movement. Both Herophilus and Erasistratus identified correctly the existence of separate sensory and motor (involved in movement) nerves in the human brain and spine.⁴

But as we've seen, long after the case for the brain (the encephalocentric view) was put forward, belief in cardiocentrism refused to go away. In the third century bc, all Stoic philosophers continued to believe that the intellect and soul reside in the heart. A particularly influential advocate at this time was the Stoic Chrysippus of Soli (277–204 bc). Among his arguments was that the mind must reside in the heart because the heart is the source of the voice, which is controlled by thought. Indeed, one of the reasons the cardiocentric view was so difficult to overturn was that many of its advocates were convinced by this kind of specious logic. They also believed the cardiocentric view must be true because it had been adhered to for so long and by so many great thinkers and poets. Incidentally, claiming that a fact must be true because it is endorsed by one or more authority figures is a hallmark of poor argument that is still used to today by those advocating pseudoscientific positions.

In the second century ad, frustrated by the continuing influence of Chrysippus and contemporary members of the cardiocentric camp, Galen “the Prince of physicians” famed for his treatment of gladiators at Pergamon, decided to perform a dramatic public demonstration in which he severed the recurrent laryngeal nerve of a pig.⁵ Cutting this nerve, which travels from the brain to the larynx (voice box), had the effect of stopping the animal from squealing as it continued to thrash about. Following the logic espoused by the cardiocentric advocates, severing nerves that originated in the brain should not have stopped the pig from squealing, unless the cardio view was wrong and speech and thought were controlled by the brain, as Galen argued. Galen's demonstration undermined their claims in what the historian Charles Gross describes as the first experimental demonstration of the brain's control of behavior.

Unsurprisingly perhaps, not everyone was convinced. Galen was heckled by, among others, the philosopher Alexander Damascenus, who said the demonstration only applied to animals. In fact, belief in the mental function of the heart persisted in many quarters all the way through to the Renaissance. Consider the writings of William Harvey, the English physician celebrated for his description of the circulation of the blood round the body. His classic work, De motu cordis et sanguinis in animalibus (published in 1628), describes the heart as the highest authority, ruling over the rest of the body. There are still hangovers from this myth to this day, in the way we allude to the psychological function of the heart in expressions like “to learn by heart,” and when we imply the heart is the seat of love.

It is important to add a note here that while cognitive function is based principally in the brain, there is growing evidence that the function of the heart certainly affects our thoughts and emotions (see pp. 163 and 166) so we ought not to be too dismissive of the cardiocentric views held by the Ancients.

Myth #2 The Brain Pumps Animal Spirits Round the Body

Some of the discoveries made by Galen and the Alexandrian anatomists seem remarkably modern. But their prescience can be misleading. The world at that time in fact knew virtually nothing about the biological brain processes that support mental function, and this remained the case for centuries to come.

For instance, despite his ground-breaking anatomical work, Galen, like most others of his time and beyond, was a strong believer that the body contains two different kinds of spirits. He thought inhaled air was transformed into “vital spirits” in the heart, and that these were converted into “animal spirits” or “pneumata psychikon” when they reached the brain. This conversion process he thought took place in the brain's hollow cavities (the ventricles) and in the rete mirabile (meaning “wonderful net”) – an intricate network of blood vessels he'd discovered in the base of the brain of several animals. In fact this network isn't found in the human brain but Galen didn't know this because he only dissected animals. Movement and sensation, Galen further theorized, are made possible by animal spirits traveling up and down the hollow nerves of the body, pumped by the brain.

The idea that animal spirits pulse through body sounds ridiculous to us today, but it was another idea, like the cardiocentric view of mental function, that showed remarkable longevity, only being debunked in the seventeenth century. One reason for its persistence was its vagueness. No one ever spelled out exactly what animal spirits are supposed to be, other than that you can't see them or feel them because they're weightless and invisible. This meant the theory could not be falsified using the technologies of the time. Today scientists recognize that any respectable theory should be logically falsifiable. That is, it ought to be possible to imagine the kinds of evidence that would indicate the theory is wrong, even if such evidence does not exist.

Another reaso...

Table of contents

• Cover
• Praise for Great Myths of the Brain
• Great Myths of Psychology
• Title page
• Copyright page
• Dedication
• Acknowledgments
• Introduction
• 1 Defunct Myths
• 2 Myth-Based Brain Practices
• 3 Mythical Case Studies
• 4 The Immortal Myths
• 5 Myths about the Physical Structure of the Brain
• 6 Technology and Food Myths
• 7 Brain Myths Concerning Perception and Action
• 8 Myths about Brain Disorder and Illness
• Afterword
• Supplemental Images
• Index
• End User License Agreement