Painfully shy, Brodmann was repeatedly overlooked for promotions despite the importance of his work and struggled for years to secure an adequate research position. His career was further sidetracked with the outbreak of World War I, when he was sent to work at a mental asylum in Tübingen. Finally, in 1917, at the age of forty-eight his luck turned. He landed an important job as head of the Department of Topographical Anatomy at an institute in Munich. At last he had the economic security to get married and have a child, both of which he did in short order. Brodmann enjoyed not quite a year of unaccustomed serenity. In the summer of 1918, eleven and a half months after his marriage, two and a half months after the birth of his child, and at the very height of his happiness, he contracted a sudden infection and within five days was dead. He was forty-nine years old.
The area that Brodmann mapped, the cerebral cortex, is the brain’s celebrated gray matter. Beneath it is the much greater volume of white matter, which is so called because the neurons are sheathed in a pale fatty insulator called myelin, which greatly accelerates the speed at which signals are transmitted. Both white matter and gray matter are misleadingly named. Gray matter isn’t terribly gray in life, but has a pinkish blush. It only becomes conspicuously gray in the absence of blood flow and with the addition of preservatives. White matter is also a posthumous attribute because the pickling process turns the myelin coatings on its nerve fibers a luminous white.
Incidentally, the idea that we use only 10 percent of our brains is a myth. No one knows where the idea came from, but it has never been true or close to true. You may not use it all terribly sensibly, but you employ all your brain in one way or another.
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The brain takes a long time to form completely. A teenager’s brain is only about 80 percent finished (which may not come as a great surprise to the parents of teenagers). Although most of the growth of the brain occurs in the first two years and is 95 percent completed by the age of ten, the synapses aren’t fully wired until a young person is in his or her mid- to late twenties. That means that the teenage years effectively extend well into adulthood. In the meantime, the person in question will almost certainly have more impulsive, less reflective behavior than his elders and will also be more susceptible to the effects of alcohol. “The teenage brain is not just an adult brain with fewer miles on it,” Frances E. Jensen, a neurology professor, told Harvard Magazine in 2008. It is, rather, a different kind of brain altogether.
The nucleus accumbens, a region of the forebrain associated with pleasure, grows to its largest size in one’s teenage years. At the same time, the body produces more dopamine, the neurotransmitter that conveys pleasure, than it ever will again. That is why the sensations you feel as a teenager are more intense than at any other time of life. But it also means that seeking pleasure is an occupational hazard for teenagers. The leading cause of deaths among teenagers is accidents—and the leading cause of accidents is simply being with other teenagers. When more than one teenager is in a car, for instance, the risk of an accident multiplies by 400 percent.
Everybody has heard of neurons, but not so many are familiar with the other main brain cells, glia or glial cells, which is a little odd because they outnumber neurons by ten to one. Glia (the word means “glue” or “putty”) are the cells that support neurons in the brain and central nervous system. For a long time, they were assumed to be not too important—their role was thought to be principally to provide a kind of physical support, or extracellular matrix as anatomists put it, for neurons—but now it is known that they engage in a lot of important chemistry, from producing myelin to clearing away wastes.
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There is quite a lot of disagreement over whether the brain can make new neurons. A team at Columbia University led by Maura Boldrini announced in early 2018 that the brain’s hippocampi definitely produce at least some new neurons, but a team at the University of California at San Francisco came to precisely the opposite conclusion. The difficulty is that there is no certain way of telling whether neurons in the brain are new or not. What is beyond doubt is that even if we do make some new neurons, it is nothing like enough to offset the kind of loss you get from general aging, never mind stroke or Alzheimer’s. So either literally or to all intents and purposes, once you pass early childhood, you have all the brain cells you are ever going to have.
On the plus side, the brain is able to compensate for quite severe loss of mass. In one case cited by the British doctor James Le Fanu in his book Why Us?, doctors scanning the brain of a middle-aged man of normal intelligence were astounded to discover that two-thirds of the space inside his skull was occupied by a giant benign cyst that he had evidently had since infancy. All of his frontal lobes and some of his parietal and temporal lobes were missing. The remaining third of his brain had simply taken on the duties and functions of the missing two-thirds and had done it so well that neither he nor anyone else had ever suspected that he was operating at a much-reduced capacity.
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For all its marvels, the brain is a curiously undemonstrative organ. The heart pumps, the lungs inflate and deflate, the intestines quietly ripple and gurgle, but the brain just sits pudding-like, giving away nothing. Nothing in its structure outwardly suggests that this is an instrument of higher thinking. As Professor John R. Searle of Berkeley once put it, “If you were designing an organic machine to pump blood you might come up with something like a heart, but if you were designing a machine to produce consciousness, who would think of a hundred billion neurons?”
So it is hardly surprising that our understanding of how the brain functions was slow in coming and largely inadvertent. One of the great (and, it must be said, most written about) events in early neuroscience occurred in 1848 in rural Vermont when a young railroad builder named Phineas Gage was packing dynamite into a rock and it exploded prematurely, shooting a two-foot tamping rod through his left cheek and out the top of his head before it clattered back to Earth about fifty feet away. The rod removed a perfect core of brain about an inch in diameter. Miraculously, Gage survived and appears not even to have lost consciousness, though he did lose his left eye and his personality was forever transformed. Previously happy-go-lucky and popular, he was now moody, argumentative, and given to profane outbursts. He was just “no longer Gage,” as one old friend reported sadly. As often happens to people with frontal lobe damage, he had no insight into his condition and didn’t understand that he had changed. Unable to settle, he drifted from New England to South America and on to San Francisco, where he died aged thirty-six after falling prey to seizures.
Gage’s misfortune was the first proof that physical damage to the brain could transform personality, but over the following decades others noticed that when tumors destroyed or impinged upon parts of the frontal lobes, the victims sometimes became curiously placid and serene. In the 1880s, in a series of operations, a Swiss physician named Gottlieb Burckhardt surgically removed eighteen grams of brain from a disturbed woman, in the process turning her (in his own words) from “a dangerous and excited demented person to a quiet demented one.” He tried the process on five more patients, but three died and two developed epilepsy, so he gave up. Fifty years later, in Portugal, a professor of neurology at the University of Lisbon, Egas Moniz, decided to try again and began experimentally cutting the frontal lobes of schizophrenics to see if that might quiet their troubled minds. It was the invention of the frontal lobotomy (though it was then often called a leukotomy, particularly in Britain).