We Are Our Brains (39 page)

A study in which epilepsy patients with electrodes implanted in their temporal lobes were shown hundreds of pictures of different faces revealed the existence of neurons that fire only when the person sees a photo of a celebrity like Bill Clinton. So it's somewhere in that part of the brain that my facial recognition problem is located. In tests on monkeys, the neurons at the base of the temporal lobe that fired when they were shown a computer-generated face fired more strongly when they saw a face they knew. The strongest response came when they were shown images in which the most typical
features of a familiar face had been caricatured—something that, given my own prosopagnosia, might explain my love of cartoons.

A recognition problem of an entirely different order occurs in Capgras syndrome. While being able to recognize a friend, partner, or close relative, the sufferer feels no emotional connection to them and is therefore convinced that they are impostors. This delusion that a loved one has been replaced by something else—a robot or extraterrestrial—leads to paranoid behavior. Capgras syndrome sometimes develops after brain damage or as a symptom of Alzheimer's.

That the various components of vision are processed in different parts of the brain can lead to very specific visual impairment. The psychologist Ed de Haan described the case of a patient who couldn't see movement. When cars were in motion, she couldn't see them, but when they stopped, they suddenly became visible. Some people can see but not recognize color or can see color but not shapes or have no perception of brightness and therefore have no idea whether they are switching a light on or off.

The safest storage place for information is our remote memory, where we keep language and music. It's the last part to be affected by Alzheimer's. Speech only disappears late in Stage 7 of the system devised by Dr. Barry Reisberg to chart the progress of the disease (see
chapter 18
). Alzheimer's sufferers can also retain musical skills much longer than other abilities. A professional pianist started to experience memory problems at the age of fifty-eight. By the time she was sixty-three, the dementia was so advanced that she could no longer retain anything that was said or written. But she was still able, on hearing a piece of music for the first time, to remember it and play it with musical feeling. Although her cognitive skills deteriorated sharply in the year that followed, she could still play the melodies she knew, an activity that gave her a great deal of pleasure. It seems that musical memory is regulated by a subsystem of the long-term memory located on the side of the brain (parietal cortex,
fig. 1
) and that it
remains relatively intact. In the case of visual artists with Alzheimer's whose artistic skills remain unimpaired, the subsystem probably lies at the rear of the brain (visual cortex,
fig. 1
), an area that is less affected—and last affected—by the progression of the disease (see
chapter 18
).

The cerebellum (
figs. 1
and
2
) is located at the back of the brain, under the large mass of the cerebral cortex. This relatively small structure (
cerebellum
is Latin for “little brain”) contains 80 percent of our neurons and ensures that our movements and speech are flowing and coordinated. When you shake your head violently, for instance, it allows you to keep your eyes fixed on one point. It contains the memory of how to do things. It keeps track of motor learning during our development, from crawling to standing and walking, then cycling, swimming, playing the piano, and driving a car, and it constantly steers performance of these tasks. The program for these complex actions—our implicit memory—is stored and updated in this remarkable little computer, allowing us to perform them completely automatically. Practice makes perfect, even in the cerebellum. When we learn to drive, we initially have to think about every action (“I need to change gear, that means using the clutch, where was third gear again?”). This involves using explicit or declarative memory, the memory of facts and events, a time-consuming and highly inefficient process. By practicing the same tasks over and over, they become fully automatic and are transferred to the implicit or procedural memory in the cerebellum. When you have driven so often that you do it without thinking, it in fact becomes difficult to say (drawing on your explicit memory) exactly what actions are involved. H.M.'s implicit memory was intact, because he could learn new motor skills.
His ability to trace a star that he could see in a mirror improved as he practiced day after day, but he could remember nothing of these exercises. He no longer possessed that first, explicit stage in which his brain consciously trained, but his cerebellum was practicing and perfecting new tasks unconsciously.

The cerebellum also suppresses the impact that your own actions have on other parts of the brain. That's why you can't tickle yourself. Your brain wants to give priority to unexpected sensory input that might require an urgent response, and your attempts at tickling yourself (like your other actions) are expected, so the sensations they produce elsewhere are suppressed. Some people lose this mechanism after damage to the cerebellum and find that they can tickle themselves as a result.

Damage to the cerebellum doesn't cause paralysis, but it does make you unbelievably clumsy. Normally, if you shut your eyes, it shouldn't be at all difficult to touch the tip of your nose with your right or left index finger. If your cerebellum is damaged because of an infarct or hemorrhage, your finger will wave about from left to right and is just as likely to land in your eye. Damage of this kind also makes it hard to walk: You stagger about with your legs wide apart, trying not to fall. A colleague of mine once stumbled off an aircraft in this way, because a blood clot had shot into his cerebellum during the long flight. Alcohol and cannabis also impair the functioning of the cerebellum and have the same impact on walking ability.

The large neurons of the cerebellum, known as Purkinje cells, form while we're still in the womb. But the vast majority of the small neurons, called granule cells, form only after birth. So all developmental brain disorders, including autism and pedophilia, make their mark on the cerebellum. The many cerebellar deviations found in all cell types and chemical messengers in autism could explain certain impaired motor functions, like problems with movement coordination and speed and difficulty in learning how to tie shoelaces or ride a bike. But besides its crucial role in movement, it's becoming increasingly clear that the cerebellum is also involved in higher cognitive
functions. Developmental disorders of the cerebellum, local damage, infarcts, or tumors can go hand in hand with a host of psychological problems, dyslexia, ADHD, impaired verbal intelligence, and learning disorders.

So the cerebellum is excellently designed for learning complex tasks and actions. But it also coordinates movements that take much less trouble to learn, like the involuntary muscle movements during orgasm. Gert Holstege, who teaches neuroanatomy at Groningen University, carried out brain scans of individuals experiencing orgasm, finding an incredible amount of activity in the cerebellum in both men and women. It makes you wonder what the world would be like if training the muscle movements involved in orgasm took as much time, patience, and effort as learning to play the piano. Problems like overpopulation, global warming, and environmental pollution would never arise!

As far as I'm concerned, the most interesting question about religion isn't whether God exists but why so many people are religious.
There are around ten thousand different religions, each of which is convinced that there's only one Truth and that they alone possess it. Hating people with a different faith seems to be part of belief. Around the year 1500, the church reformer Martin Luther described Jews as a “brood of vipers.” Over the centuries the Christian hatred of the Jews led to pogroms and ultimately made the Holocaust possible. In 1947, over a million people were slaughtered when British India was partitioned into India for the Hindus and Pakistan for the Muslims. Nor has interfaith hatred diminished since then. Since the year 2000, 43 percent of civil wars have been of a religious nature.

Almost 64 percent of the world's population is Catholic, Protestant, Muslim, or Hindu. And faith is extremely tenacious. For many years, Communism was the only permitted belief in China and religion was banned, being regarded, in the tradition of Karl Marx, as the opium of the masses. But in 2007, one-third of Chinese people over the age of sixteen said that they were religious. Since that figure comes from a state-controlled newspaper, the
China Daily
, the true number of believers is likely at least that high. Around 95 percent of Americans say that they believe in God, 90 percent pray, 82 percent believe that God can perform miracles, and over 70 percent believe in life after death. It's striking that only 50 percent believe in hell, which shows a certain lack of consistency. In the Netherlands, a much more secular country, the percentages are lower. A study carried out in April 2007 showed that in the space of forty years, secularization had increased from 33 to 61 percent. Over half of the Dutch people doubt the existence of a higher power and are either agnostic or believe in an unspecified “something.” Only 14 percent are atheists, the same percentage as Protestants. There are slightly more Catholics (16 percent).

In 2006, during a symposium in Istanbul, Herman van Praag, a professor of biological psychiatry, taking his lead from the 95 percent of believers in the United States, tried to convince me that atheism
was an “anomaly.” “That depends on who you compare yourself to,” I replied. In 1996 a poll of American scientists revealed that only 39 percent were believers, a much smaller percentage than the national average. Only 7 percent of the country's top scientists (defined for this poll as the members of the National Academy of Sciences) professed a belief in God, while almost no Nobel laureates are religious. A mere 3 percent of the eminent scientists who are members of Britain's Royal Society are religious. Moreover, meta-analysis has shown a correlation among atheism, education, and IQ. So there are striking differences within populations, and it's clear that degree of atheism is linked to intelligence, education, academic achievement, and a positive interest in natural science. Scientists also differ per discipline: Biologists are less prone to believe in God and the hereafter than physicists. So it isn't surprising that the vast majority (78 percent) of eminent evolutionary biologists polled called themselves materialists (meaning that they believe physical matter to be the only reality). Almost three quarters (72 percent) of them regarded religion as a social phenomenon that had evolved along with
Homo sapiens.
They saw it as part of evolution, rather than conflicting with it.

It does indeed seem that religion must have afforded an evolutionary advantage. Receptiveness to religion is determined by spirituality, which is 50 percent genetically determined, as twin studies have shown. Spirituality is a characteristic that everyone has to a degree, even if they don't belong to a church. Religion is the local shape given to our spiritual feelings. The decision to be religious or not certainly isn't “free.” The surroundings in which we grow up cause the parental religion to be imprinted in our brain circuitries during early development, in a similar way to our native language. Chemical messengers like serotonin affect the extent to which we are spiritual: The number of serotonin receptors in the brain corresponds to scores for spirituality. And substances that affect serotonin, like LSD, mescaline (from the peyote cactus), and psilocybin (from magic mushrooms) can generate mystical and spiritual experiences. Spiritual
experiences can also be induced with substances that affect the brain's opiate system.

Dean Hamer believes that he has identified the gene that predisposes our level of spirituality, as he describes in
The God Gene
(2004). But since it will probably prove to be simply one of the many genes involved, he'd have done better to call his book
A God Gene.
The gene in question codes for VMAT2 (vesicular monoamine transporter 2), a protein that wraps chemical messengers (monoamines) in vesicles for transport through the nerve fibers and is crucial to many brain functions.