We Are Our Brains (3 page)

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).

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 psychiatric 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.

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.