We Are Our Brains (7 page)

FIGURE 7.
On the left, a scan of the brain of a three-year-old child who was brought up normally. On the right, the brain of a three-year-old child who was severely neglected. The neglected child has a much smaller brain, with larger ventricles (the brain cavities, shown in black). There are also much larger spaces between the convolutions of the brain due to shrinking of the cerebral cortex. Based on B. D. Perry, 2002.

FIGURE 8.
Broca's area (frontal, associated with the ability to speak) and Wernicke's area (temporal, associated with the ability to understand language). These centers are also closely involved in processing music and singing. Music and language are very much interrelated.

The brain circuitry necessary for our memory matures only in our first years of life, and conscious memories mostly start from the age of two. There are exceptions; some people have very detailed, verifiable memories of events that go back further. But the general absence of memory prior to the age of two doesn't mean that information from the outside world doesn't penetrate a child's brain. It's a fact that unborn babies respond to external stimuli, but their ability to retain memories from this time hasn't been demonstrated. Are we indeed born as a tabula rasa, a blank slate, as the early Enlightenment philosopher John Locke thought, or with a treasure trove of memories of the best time of our lives, as the painter Salvador Dalí would have us believe?

There's no lack of speculation about the mental baggage we bring with us into the world and the influence that our time in the womb allegedly has on the rest of our lives. “Prenatal universities” have been set up in the United States, at which mothers learn to interact with their unborn children. It's true, your intrauterine history determines your risk of many psychiatric disorders, like schizophrenia and depression. But some therapists go too far when they maintain that traumatic memories from the fetal period are the cause of very specific psychiatric problems later in life. It's been claimed that some headaches in adult life are due to forceps delivery or pain during childbirth. Some blame women's obstetric or gynecological problems on a feeling of being unwanted at birth, because they were girls. Others attribute a penchant for bondage to being entangled in the umbilical cord at birth or a fear of being crushed to a long, difficult passage through the mother's narrow pelvis. Luckily, the same
therapists reassure patients that problems like this can easily be solved by regression therapy, the theory being that to identify the cause of your problems is to solve them. A forensic study compared 412 suicide victims who were alcoholics and drug addicts with 2,901 people in a control group. A link was made between events around birth and self-destructive behavior. Suicides by hanging were associated with oxygen deprivation at birth, violent suicides with mechanical birth trauma, and drug addiction with the administration of addictive substances like painkillers during labor. A recent independent Dutch study, however, found no link between opiates administered as painkillers at birth and subsequent addiction. I'm very curious to know the results of future attempts to confirm the other correlations.

Dalí did not need regression analysis or LSD to remember his intrauterine stay in detail, which he recalled as heavenly. “The intrauterine paradise was the color of hell, that is to say, red, orange, yellow and bluish, the color of flames, of fire; above all it was soft, immobile, warm, symmetrical, double, gluey.” His most splendid memory was of two fried, phosphorescent eggs. Dalí said he could reproduce a similar image at will by pressing on his closed eyelids (“characteristic of the fetal posture”). Those fried eggs return in many of Dalí's paintings. Indeed, the human fetus does respond to light from the twenty-sixth week of pregnancy. But even if Dalí's mother had lain in the sun in her bikini during her pregnancy, which is highly unlikely, the little Salvador wouldn't have been able to observe much more than a diffuse orange glow. So it would seem that detailed visual memories are the privilege of Surrealists.

However, other types of fetal memory have been demonstrated in a number of species. It's undoubtedly useful for a baby bird to become familiar with the call of its parents while still in the egg. The same applies to humans: The bond between mother and child is first established during pregnancy through the mother's voice. The existence of fetal memory in humans has been shown from three experimental paradigms: habituation, classic conditioning, and
exposure learning. Habituation is the simplest form of memory, whereby the reaction to a stimulus declines the more it is encountered. In the human fetus, habituation is present as early as the twenty-second week of pregnancy. Classic conditioning has been demonstrated from the thirtieth week. Vibrations, for instance, have been used as the “conditioned stimulus” (akin to the bell in Pavlov's famous experiment with dogs), while a loud noise has been the “unconditioned stimulus” (akin to the food in Pavlov's experiment). But the level of the nervous system at which this type of learning takes place is debatable. Since an anencephalic fetus (a baby with most of its brain missing,
fig. 4
) can also be conditioned in this way, such learning may take place at the level of the brain stem or spinal cord. The experiments to determine exposure learning produced a much more interesting finding: When a pregnant woman relaxed every time she heard a particular piece of music, after a while the fetus began to move as soon as the music started. After birth, the same child stopped crying and opened its eyes on hearing the same music. Hearing the mother's voice while in the womb could play a role in the development of language and the bond between mother and child. Newborn babies prefer their mother's voice, particularly if it's distorted in the way that it would have been in the womb. They can also recognize a story repeatedly read aloud by the mother during pregnancy. However, the fetal memory for sounds has its dangers. Newborn babies show a clear response when they hear the theme tune of television soaps obsessively watched by their mothers during pregnancy. They stop crying and listen alertly to the highly familiar tune, and you wonder whether they are doomed to be addicted to such programs when they grow up. The unborn child's great sensitivity to melody might also explain why French babies cry with a rising intonation and German babies with a falling intonation, reflecting the different intonation contours of the two languages. Might this be the first expression of musical ability?

Babies can also remember scent and taste stimuli from the womb. Their mother's smell is instantly recognized after birth, which may
be important to successful breast-feeding. Newborn babies normally dislike the smell of garlic, but if a woman eats garlic during pregnancy, her baby will not be averse to its smell. It is interesting to note that culinary differences between the French and the Dutch go back all the way to intrauterine experiences!

In sum, the fetus has a memory of sound, vibration, taste, and smell. So it's possible that we're ruining our children's brains not just by smoking and drinking and by taking medicine and other drugs but also by watching bad television programs. In other words, you'd do well to pick up a good book now and again and read to your unborn child in the hope that the next generation will rediscover literature. And that's not a new idea, by the way, because as far back as
A.D.
200–600, the Talmud made mention of prenatal stimulation programs. But memories of the womb aren't detailed and as far as we know disappear within a few weeks, instead of lasting a lifetime, as some therapists and Salvador Dalí would have us believe.

Our brains develop with incredible rapidity before birth and in the years immediately after. Moreover, each tiny area of the brain and each cell type within that area develops at a different tempo. During this period of explosive growth, brain cells are extremely susceptible to a number of different factors. First, for the brain to develop normally, the unborn child needs sufficient nourishment. Its thyroid gland also needs to function properly. At this stage, brain development is determined in general by our genetic background and in detail by the activity of our nerve cells. These, in turn, are influenced by the availability of nutrients, chemical messengers from other brain cells (neurotransmitters), growth regulators, and hormones. At that stage, the unborn child's sex hormones regulate the sexual differentiation of the brain. Substances that enter the fetal system via the placenta can derail the delicate process of brain development. These can either come from the environment or be ingested
by the expectant mother (for instance, alcohol, nicotine, and other addictive substances and medications).

Sadly, we live in a world in which 200 million children suffer from serious and lasting brain damage due to lack of nourishment. Not only is their mental capacity impaired; they also have an increased risk of schizophrenia, depression, and antisocial behavior. This was shown by a study of children born in the major Dutch cities during the famine (“Hunger Winter”) of 1944–1945 (
fig. 9
). Even in today's affluent society the same problem still occurs when a placenta malfunctions, depriving the fetus of nourishment and causing it to be undersized at birth. Malnutrition in the womb can also occur when a pregnant woman vomits excessively, tries to keep her weight down by dieting, or eats too little because of the Ramadan fast.

Some 200 million people live in regions with an iodine shortage, which affects their children's growth. Such places aren't necessarily remote; they can be found all over the world. Thyroid hormones are necessary for normal brain development but can only function if sufficient iodine is incorporated into the hormone. This happens in the thyroid gland. In mountainous areas, the iodine found naturally in soil can be washed away by rainwater. The resulting shortage of iodine affects the functioning of a child's thyroid hormones, leading to impaired brain and inner ear development. Such children develop huge thyroids that desperately try to store every scrap of iodine ingested. In the worst cases, thyroid hormone deficiency results in cretinism, a condition of severely stunted mental and physical growth. The endocrinologist Dries Querido made it his life's work to find remote places with an iodine shortage. I remember him calling me late one evening to ask if I could get him a sixteen-millimeter film projector for a lecture he had to give the next day in Amsterdam. That was how I became one of the first people to see a film he had shot in the Mulia Valley in New Guinea, then still a Dutch colony—a remote spot that could be reached only by a Cessna airplane—and hear about his expedition's findings. Around 10 percent of the children in that valley were mentally deficient and deaf and had serious
neurological disorders. Querido proved that this was caused by iodine deficiency, and he treated the locals with an injection of Lipiodol, an oil containing iodine. Formerly used as a contrast agent in X-ray photos of the lungs, it was found to be potentially damaging to lung tissue. However, it turned out to be extremely effective as a depot injection to treat iodine deficiency. Similarly, the simple remedy of adding iodine to kitchen salt led to the closure of every single institution for deaf-mutes in Switzerland. In the twenty-first century, I myself witnessed developmental disorders resulting from iodine deficiencies in the mountains of Anhui, China. A woman suffering from cretinism—and disfigured by a huge goiter—was sweeping away leaves at a temple. When one of the members of our team, a Chinese professor, asked the woman if she would like to see a doctor, she merely growled and waved her broom threateningly at us.