We Are Our Brains Read online

  My research group was also involved in setting up the first study on Alzheimer’s disease in the Netherlands, at a time when the epidemic proportions of the disease were merely conjecture. Our observation that some brain cells could withstand the aging process and Alzheimer’s unscathed while others were destroyed was important in guiding our research of therapeutic strategies for the disorder (see chapter 18). Demographic aging means that many of us now have to see loved ones deteriorate during the last stage of life as a result of dementia. Most of us also experience the huge pressure that psychiatric disorders impose on the lives of patients, relatives, and carers. The questions about these conditions that I am confronted with as a brain researcher go so deep that I can’t avoid them.

  The general public, blissfully unaware of our daily battles with the technical problems of research, assumes that we know everything about the brain. People want answers to the big questions about memory, consciousness, learning and emotion, free will, and near-death experiences. As a researcher, if you don’t fend off those types of queries, you’ll get sucked into them sooner or later and discover that they are riveting.

  Discussions about the brain always reveal how firmly convinced people are of “facts” whose origins are a mystery to me. Take the myth that we use only 10 percent of our brains. You might well be forgiven for thinking this in the case of certain people, but I haven’t the faintest idea what prompted this crazy theory. The same goes for the claim that millions of our brain cells die off every day. But lack of expertise can also be refreshing. When I give lectures, I often get asked intriguing questions by members of the audience. Sometimes even children raise the most thought-provoking issues. One Dutch girl of Japanese origin wanted to write a school assignment on the difference between European and Asian brains—differences that do exist but are rarely acknowledged.

  On top of general inquiries, I also had to contend over the years with an avalanche of questions and a heated public response to my own research on the human brain, prompting the need for explanation and debate on issues like gender-based differences in the brain, sexual orientation, transsexuality, brain development, and brain disorders like depression and eating disorders (see chapters 1, 2, 3, and 5).

  In the forty-five years that I’ve been active in this field, brain research has developed from the preserve of a few mavericks into a global discipline that has rapidly brought a host of new insights, thanks to the efforts of many tens of thousands of researchers representing many different disciplines and employing highly diverse techniques. The general neurophobia of the old days has been transformed into an overwhelming fascination with everything connected to the brain, partly thanks to excellent science journalism. Unable to escape the questions that the public was posing, I found myself constantly compelled to step aside from my own line of research to think about every conceivable aspect of the brain and how it could all be explained to a general readership. In this way I developed my own views on features of the brain and our emergence as humans, on the way in which we develop and age, on the origins of brain disorders, and on life and death. Over the course of time my own little answers to and ideas about the big brain questions took shape. They are set out in this book.

  The question I am most frequently asked is whether I can explain how the brain works. That’s a conundrum that has yet to be fully solved, and this book can of course provide only a partial answer. It shows how our brains differentiate into male and female brains, what goes on in the adolescent mind, how the brain preserves the individual and the species, how we age, how we suffer from dementia and die, as well as how the brain evolved, how memory works, and how moral behavior developed. But the book also shows how things can go wrong. It looks at disorders of consciousness, brain damage caused by boxing, and diseases of the brain like addiction, autism, and schizophrenia, as well as the latest medical advances and possibilities for recovery. Finally, it looks at the relationship between the brain and religion, the soul, the mind, and free will.

  The various sections of this book can be read separately. In such a short space that deals with so many different subjects, it’s impossible to arrive at deep scientific conclusions. These thoughts are intended to prompt further debate about why we are as we are, how our brains develop and function, and how they can malfunction. I hope that this book can provide a general readership with answers to many frequently asked questions about the brain. I also hope it will give students and young brain researchers an introduction to neuroculture, encouraging them to cross the borders of their research and engage in dialogue with the general public. That this is necessary is self-evident, not just in view of the social impact of brain research but also because of the support that we, for our part, ask from society for our research.

  FIGURE 1. The brain seen from the side, facing left, with the parts of the cerebral cortex labeled. F is the frontal lobe (planning, initiative, speech, motor system), which contains the primary motor cortex (fig. 22). P is the parietal lobe, which contains the primary sensory cortex (fig. 22) and integrates sensory information (sight, touch, navigation). This part of the brain is also used for reasoning and calculation, and stores information on the significance of numbers as well as an inner body map. O is the occipital lobe (visual cortex). T is the temporal lobe (memory, hearing, language; fig. 21). At the base is C, the cerebellum (automatic movements and coordination), and B, the brain stem (regulates breathing, heartbeat, temperature, waking and sleeping).

  Introduction

  WE ARE OUR BRAINS

  It should be widely known that the brain, and the brain alone, is the source of our pleasures, joys, laughter, and amusement, as well as our sorrow, pain, grief, and tears. It is especially the organ we use to think and learn, see and hear, to distinguish the ugly from the beautiful, the bad from the good, and the pleasant from the unpleasant. The brain is also the seat of madness and delirium, of the fears and terrors which assail us, often at night, but sometimes even during the day, of insomnia, sleepwalking, elusive thoughts, forgetfulness, and eccentricities.

  Hippocrates

  Everything we think, do, and refrain from doing is determined by the brain. The construction of this fantastic machine determines our potential, our limitations, and our characters; we are our brains. Brain research is no longer confined to looking for the cause of brain disorders; it also seeks to establish why we are as we are. It is a quest to find ourselves.

  The brain is built from nerve cells called neurons. Weighing around three pounds, the brain contains 100 billion neurons (fifteen times the number of people on earth). And the neurons are outnumbered ten to one by glial cells. It was formerly thought that they were only there to hold neurons together (glia comes from the Greek word for “glue”). But recent studies show that these cells, of which humans possess more than any other organism, are crucial to the transfer of chemical messages and therefore to all brain processes, including the formation of long-term memory. That sheds interesting light on the finding that Einstein’s brain contained unusually many glial cells.

  The product of the interaction of all these billions of neurons is “mind.” Just as kidneys produce urine, the brain produces mind, as Jacob Moleschott (1822–1893) so inimitably put it. But now we know what this process actually entails: electrical activity, the release of chemical messengers, changes in cell contacts, and alterations in the activity of nerve cells (see above and chapter 14). Brain scans are used not only to trace diseases of the brain but also to show which areas light up during different activities, so that we know which parts we use to read, think, calculate, listen to music, have religious experiences, fall in love, or become sexually excited. By observing changing patterns of activity in your own brain, you can train it to function differently. With the aid of a functional scanner, for instance, patients suffering from chronic pain can be coached to control activity in the front of the brain, thereby reducing their pain.

  Malfunctions in this efficient information-processing machine cause psychiatri
c and neurological disorders. Paradoxically, these disorders tell us much about the way in which the brain normally functions. Effective therapies have already been devised for some of these conditions. Parkinson’s disease has been treated with L-dopa for a long time now, and combination therapy for AIDS now staves off dementia. Genetic and other risk factors for schizophrenia are being rapidly charted: Under the microscope you can see that brain development in schizophrenia sufferers is impaired before they are even born. Schizophrenia can now be treated with medication.

  Until recently, neurologists could do little more than pinpoint the exact location of the brain defect you were stuck with for life. Nowadays, the clots that cause strokes can be broken down, hemorrhages stanched, and stents inserted into clogging arteries. Over 3,500 people have donated their brains to the Netherlands Brain Bank (www.brainbank.nl), leading to new insights in the molecular processes that cause diseases like Alzheimer’s, schizophrenia, Parkinson’s, multiple sclerosis, and depression. The search for new approaches to medication is also in full swing. But research of this kind will only bear clinical fruit for the next generation of patients.

  Stimulation electrodes, implanted at exactly the right spot inside the brain, are proving effective. They were first tried on patients with Parkinson’s disease (fig. 23). It’s impressive to see how violent tremors suddenly disappear when the patients themselves press the button of the stimulator. Depth electrodes are already being used to treat cluster headaches, muscle spasms, and obsessive-compulsive disorder. They help patients who had previously washed their hands hundreds of times a day to lead a normal life. A depth electrode was even used to revive someone who had spent six years in a minimally conscious state. Attempts are being made to treat obesity and addiction with depth electrodes. As always, it takes a while before not only the effects but also the side effects of a new therapy come to light—as is now happening with deep brain stimulation (see chapter 11).

  Magnetic stimulation of the prefrontal cortex (fig. 15) has been successfully used to treat depression, and stimulation of the auditory cortex silences the incredibly annoying tunes that can suddenly start playing in the heads of people with inner ear hearing loss. Transcranial magnetic stimulation (see chapter 10) has proved effective in treating hallucinations provoked by schizophrenia.

  Neuroprostheses are getting better and better at replacing our senses. At present, over one hundred thousand people have cochlear implants that enable them to hear surprisingly well. Trials are being concluded with electronic cameras that transmit information to the visual cortex (fig. 22) of blind patients. A tiny square with ninety-six electrodes was implanted in the cerebral cortex of a twenty-five-year-old man who had become completely paralyzed after being stabbed in the neck. Merely by thinking of movements he could use a computer mouse, read his email, and play electronic games. The power of thought has even been used to control a prosthetic arm (see chapter 11).

  Attempts are being made to carry out cerebral repairs by transplanting pieces of fetal brain tissue into the brains of patients with Parkinson’s disease and Huntington’s disease. Gene therapy is already being tested on people with Alzheimer’s. Stem cells appear highly suitable for repairing brain tissue, but considerable problems, like the possible growth of tumors, still need to be overcome (see chapter 11).

  Disorders of the brain are still very difficult to treat, but the era of defeatism has given way to excitement at new insights and optimism about new methods of treatment in the near future.

  METAPHORS FOR THE BRAIN

  Throughout the ages people have tried to articulate the brain’s function in terms of the latest technological advances. In the fifteenth century, for instance, during the Renaissance, at a time when printing was being developed in Europe, the brain was described as “a book containing everything” and language as “a living alphabet.” In the sixteenth century the working of the brain was compared to a “theater in the head,” and a parallel was also drawn between the brain and a cabinet of curiosities, or a museum in which you could store and view everything. The philosopher Descartes (1596–1650) regarded the body and the brain as a machine, famously comparing the brain to a church organ. He likened the air pumped into the organ by the bellows to the subtlest and most active particles in the blood, “the animal spirits,” which he thought were pushed into the cavities of the brain via a system of blood vessels (now known as the choroid plexus). Hollow nerves then transported the animal spirits to the muscles. The pineal gland played the part of the keyboard. It could direct the animal spirits into “certain pores,” just as an organist can direct air into certain pipes by pressing a particular key. As a result Descartes has gone down in history as the founder of mind-body dualism, a school of thought that bears his Latinized name: Cartesianism. The ancient Greeks, however, should be credited as the real inventors of dualism, as they already distinguished between body and spirit.

  If you regard the brain as a rational, information-processing, organic machine, then the computer metaphor of our time isn’t such a bad one. It’s a comparison that’s hard to avoid, especially if you consider the impressive figures about our brains’ building blocks and their connections. There are 1,000 times 1,000 billion points at which neurons connect with one another—or, as Nobel Prize winner Santiago Ramón y Cajal put it, “hold hands”—through junctions called synapses. The neurons are linked by over sixty thousand miles of nerve fiber. The staggering number of cells (see above) and contacts works so efficiently that a typical brain’s energy consumption is equal to that of a fifteen-watt lightbulb. Neuroscientist Michel Hofman has calculated that the total energy bill of a single brain during an entire lifetime of eighty years wouldn’t exceed $1,500 at today’s rates. You certainly couldn’t get a decent computer for that price, nor would it last anywhere near as long. For a mere fifteen hundred dollars you can power a billion neurons for your entire lifetime! And your skull comes fitted with a fantastically efficient machine with parallel circuits that can process images and associations better than any computer yet built. It’s always an awe-inspiring moment when you carry out a postmortem and hold a person’s brain in your hands. You’re conscious that you’re holding someone’s entire life. Of course, you’re also immediately aware of how very “soft” the “hardware” of our brain actually is. This gelatinous mass contains everything that this person thought and experienced, coded and recorded in structural and molecular changes to the synapses.

  A better metaphor comes to mind when you visit the underground command center in the heart of London where, starting in 1940, Winston Churchill led his war cabinet and a huge staff night and day in efforts to defeat Adolf Hitler. The war rooms are covered in maps displaying all the information (coded and uncoded) that came in from a vast network of lines of communication spanning the globe. Priority was given to the most up-to-date reports, which were checked, evaluated, processed, and stored by a host of well-coordinated departments. Using the information selected (by the front part of the brain, the prefrontal cortex, fig. 15) a draft plan was drawn up, elaborated, and tested based on assessment of all available data. Constant consultations were carried out with an army of specialists, both internal and external, connected by a direct link with America. After weighing all the opinions and information, a plan was either given the green light or shelved. Plans could be carried out by the army (the motor functions), the navy (hormones), units operating stealthily behind the lines (the autonomic nervous system), or the air force (neurotransmitters, cleverly targeting a single brain structure). Most effective of all, of course, was a coordinated operation involving all branches of the service. Yes, our brains are much more like a complicated command center, equipped with the latest apparatus, than a telephone switchboard or a computer with simple one-on-one connections. The command center is engaged in a lifelong battle, first to be born, then to pass exams, to obtain some means of subsistence, to fight off competition, to survive in a sometimes hostile environment, and ultimately, to die as one would wish
. It’s protected not by the bombproof concrete of Churchill’s underground headquarters but by a skull strong enough to survive some very hard knocks. Churchill himself hated his shelter and would stand on the roof during air raids, following the action. He was happy to take risks, an innate quality of some brains.

  One could also think of more peaceful metaphors, like the air traffic control center of a large airport. But if you look back at all the metaphors of previous centuries, you realize that you’re simply comparing the most recent technology devised by our brains to the brain itself. Indeed, there appears to be nothing more complex than that fantastic machine.

  FIGURE 2. Cross section of the brain. (1) The cerebrum, with the convoluted cerebral cortex. (2) The corpus callosum, a bundle of neural fibers connecting the left and right sides of the brain. (3) The pineal gland, which at night secretes the sleep hormone melatonin, a substance that also inhibits puberty in young children. (4) The fornix, which transports memory information from the hippocampus to the mammillary bodies at the base of the hypothalamus (fig. 25), after which it travels on to the thalamus (5) and cortex (1). (5) The thalamus, where sensory information and memory information are sent. (6) The hypothalamus, which is crucial to the survival of the individual and the species. (7) The optic chiasma, where the optic nerves cross. (8) The pituitary gland. (9) The cerebellum. (10) The brain stem. (11) The spinal cord.