We Are Our Brains (9 page)

We're programmed in the womb for life after birth. We acquire our feeling of being male or female, our sexual orientation, and our level of aggression while still in the womb (see
chapters 3
and
8
). Later, our sex hormones activate the brain systems that are programmed before birth, and our sexuality and aggression are manifested. This intrauterine programming is influenced by the hereditary information passed on by our parents. As a result, a significant part of our character is determined from the moment of conception, as is our risk of brain disorders like schizophrenia, autism, depression, and addiction (see
chapters 5
and
10
). But the information in our DNA is much too limited to program our brains fully in advance. The brain has solved this problem by overproducing cells and synapses. As cells develop, they compete for the best contacts. From these they obtain growth substances that make them more active, enabling them to make more and better connections. Cells that fail to do so die off, and surplus connections are pruned off.

Besides our genetic determination, our developing brains are influenced by all kinds of other factors that affect brain cell activity, like fetal and maternal hormones and nutrients and environmental chemicals passing through the placenta. For instance, sex hormones program us along male or female lines. Our levels of aggression and stress are set before birth for the rest of our lives. Extreme signals from the outside world also lead to fetal brain systems being permanently modified. In this way, the unborn child prepares itself for a hard life outside the womb. In the short term the fetal brain's plasticity promotes survival, but it also makes it more vulnerable to harmful
substances like nicotine. In the long term, fetal programming can also contribute to chronic diseases, as a study at Amsterdam's Academic Medical Center shows. Toward the end of the Second World War, the Nazi occupiers of the Netherlands robbed the country of its food supply, leading to the famine of 1944–45. Babies were not only underweight at birth (
fig. 9
) but also more likely to develop antisocial behavior and obesity in later life. They turned out to prefer fatty foods and to exercise less. They were also more likely to develop high blood pressure, schizophrenia, and depression. The implications are far-reaching because the same mechanisms still come into play when fetuses are malnourished because of placental malfunction, causing babies to be born underweight.

It seems that even before birth, a child registers a shortage of food in its surroundings. What evolutionary advantage might this have? In such cases, all the brain systems that regulate metabolism are programmed in the womb so as to retain every calorie. Later in life, these individuals feel less satiated when they eat. Since they're smaller at birth, they also need less food. So even at this early stage, children adapt their brains and behavior to a life of scarcity outside the womb. Their tendency to antisocial behavior equips them to defend their own interests, giving them an advantage in situations where there isn't enough to go around. Their activated stress axis will also contribute to this survival strategy. But if they are then born into surroundings where there's an abundance of food, this adaptive strategy becomes a handicap. Their inability to feel satiated means they are more likely to be obese and to develop hypertension. They also run a greater risk of addiction. And the fact that their stress axis is constantly switched on heightens their risk of depression and schizophrenia. So the diseases that are more likely to arise after prenatal malnutrition could be regarded as the side effects of an adaptive strategy that improves the fetus's chance of survival in the short term.

Disruption to the sexual differentiation of an unborn child's brain when its mother is severely stressed during pregnancy (see
chapter 3
)
could be regarded in a similar light. When a pregnant woman experiences stress, the brain of a female fetus will become more male and vice versa. This also appears to be an adaptive response. A girl will be able to cope better in later life if she's robust and competitive, while a boy who isn't macho is less likely to get into conflict with alpha males in that stressful environment. This is also an excellent survival strategy in the short term, but in the long term it can impair reproduction and increase the likelihood of developmental disabilities and schizophrenia.

In sum, the fetus appears only to think of survival in the short term, adapting to the difficult circumstances that it anticipates immediately after birth. It's of course wrong to speak of a fetus “thinking.” Over a period of millions of years, unborn children have been exposed to threats of this kind. Occasionally, a baby possessed a mutation that enabled it to adapt better to the problems facing it, and
this favorable mutation then spread through the population. And you can't blame a child for opting for short-term adaptations without taking account of the long-term consequences, because longevity is only a very recent human accomplishment.

FIGURE 9.
A child born in Amsterdam's Wilhelmina Gasthuis hospital during the famine (the “Hunger Winter”) of 1944–45. Not only did these babies have low birth weight, in adulthood they were more prone to antisocial behavior and obesity. They showed a preference for fatty foods and were less likely to exercise. They also had greater risk of developing high blood pressure, schizophrenia, depression, and addiction. Photograph: NIOD Institute for War, Genocide and Holocaust Studies.

Up to now, doctors have been able to treat only the later consequences of fetal programming. Now, armed with knowledge about such programming, doctors can encourage targeted prevention by providing advice on nutrition during pregnancy, for instance.

When George W. Bush was president, impressive footage of a fetus in the womb being touched by a needle and responding with violent movements made the rounds. Pro-life advocates used the video to suggest that fetuses feel pain and will attempt to protect themselves from instruments of abortion. The federal government considered making it mandatory for doctors to inform women that there was “substantial evidence” that an abortion would inflict pain on a fetus. In the case of pregnancies of over twenty-two weeks, it was proposed that anesthesia must be administered to fetuses before an abortion. Doctors who failed to comply would be fined $100,000 and lose their jobs. These proposals met with approval from the pro-life movement, but how much actual evidence is there to show that fetuses truly feel pain?

In a mature state of development, painful stimuli are transported by nerve fibers from the skin via the spinal cord to the center of the brain, the thalamus (
fig. 2
). From there, the stimuli go to two areas: the primary sensory cortex, where one becomes aware of pain, and the cingulate cortex, the brain's alarm center (
fig. 27
), which interprets pain and directs the emotional and autonomic responses: emotion, contorted face, stress response, rapid breathing, higher blood pressure, and increased heart rate.

A normal pregnancy lasts for forty weeks. The wiring to conduct
pain stimuli from the fetus's cerebral cortex is in place by the twenty-sixth week. Only then can such stimuli travel from the skin to the child's cerebral cortex, but whether they are then consciously received has yet to be established. It seems unlikely that premature babies can consciously feel pain before the twenty-ninth or thirtieth week. The pain sensors in the skin and the nerve pathways that convey pain signals are in place as early as the seventh week, enabling the fetus to respond to touch from a needle. But, contrary to the claims of fanatical pro-lifers, that certainly doesn't constitute proof that the fetus can feel pain. For that to happen, the stimulus must first reach the cerebral cortex, and the cortex must be mature enough to process stimuli meaningfully. Before the cortex is fully mature, the fetal response to pain stimuli is purely based on spinal-cord reflexes. Anencephalic babies, who are born with most of the brain missing, respond in exactly the same way. In their case, the response to pain stimuli is just as violent and generalized—the whole body seems to be involved—as in intact fetuses in the first trimester of pregnancy, precisely because the cerebral cortex hasn't matured and can't keep the spinal-cord reflex in proportion.

Contacts between the thalamus and the cortical plate under the cerebral cortex are established from twelve to sixteen weeks. The cortical plate is a waiting room for fibers that will grow into the cerebral cortex (between twenty-three and thirty weeks). EEG measurements, which determine electrical activity in the brain, and blood circulation in the cerebral cortex of premature babies show a response to pain stimuli from twenty-five to twenty-nine weeks. So at that stage, pain stimuli are arriving in the cerebral cortex. The question is whether the cerebral cortex is already mature enough to receive the pain consciously. Conscious perception is also necessary for pain to be perceived emotionally. EEG measurements in newborns show a difference between the response to touch and the response to the pain of a heel prick only as of thirty-five to thirty-seven weeks.

Nowadays, when treating premature babies in incubators, it's generally
thought to be safer to assume that they feel and experience pain. They respond to invasive treatment and the taking of blood through movement and alterations in heart rate, breathing, blood pressure, oxygen pressure, and stress hormone levels. The same applies to operations like circumcision. That doesn't prove, however, that pain is perceived consciously, because these autonomic responses come from regions below the cerebral cortex and therefore might be based on unconscious processes. The same applies to the movements that premature babies make in response to pain stimuli, because these can still be spinal-cord reflexes that don't penetrate through to the cerebral cortex. Not only do anencephalic babies respond to physical stimulus by recoiling, but brain-dead adults in vegetative comas whose cerebral cortex is entirely destroyed also respond in the same way.

So premature babies are seen to respond to pain stimuli in the cerebral cortex as of twenty-five to twenty-nine weeks, but even then we can't be certain that this response is conscious. It's even harder to establish whether a fetus possesses consciousness. The “waking stage” in a fetus's wake and sleep cycles is sometimes regarded as a surrogate for consciousness. But during the late stage of pregnancy, fetuses spend around 95 percent of the time asleep, that is, unconscious, due to the immaturity of their brains and the effects of placental hormones. During the remaining 5 percent of the time, they are “awake,” but that period is more like a transitional phase between REM and non-REM sleep than a period of genuine wakefulness or consciousness.

Unpleasant stimuli have been shown to cause changes in cerebral cortex activity in premature babies aged twenty-five to twenty-nine weeks, but there are great differences between a premature baby and a fetus of the same age. Stimuli that prompt a waking response after birth (like a shortage of oxygen) have the completely opposite effect on a fetus: They suppress the waking stage. This allows a fetus to conserve energy in difficult circumstances that it's powerless to escape anyway. Even a potentially “painful” or “annoying” stimulus,
like a strong vibration or a loud noise, elicits only a subcortical response in a fetus. Moreover, that a twenty-eight-week-old fetus can “learn” to respond to the stimulus doesn't mean that a conscious memory process is involved. Again, primitive “learning behavior” of this type can also be seen in anencephalic babies. So it's an unconscious form of learning for which the cerebral cortex isn't needed.

As for mandatory anesthesia for fetuses in the case of abortion, one might argue that if it doesn't benefit, it at least can't harm, but abortion under a general anesthetic does increase the risk of complications for the mother. For the same reason, it would be greatly worrying if doctors were obliged to anesthetize fetuses undergoing interventions other than abortion, given that there's no hard evidence that fetuses possess consciousness, whereas there is proof that anesthesia can impair a child's later development.

From all this I conclude that in the case of abortions or interventions in utero up to the twenty-fifth or twenty-sixth week of pregnancy, a general anesthetic is unnecessary for the fetus and may entail extra risks for the mother, that a premature baby should be anesthetized before undergoing painful treatment just in case, and that it should be mandatory to anesthetize boys undergoing circumcision.

During our early development, not only is our gender identity and our sexual orientation programmed in our brains (see
chapter 3
) but the functioning of our inner body map is as well. Body Integrity Identity Disorder (BIID) is a bizarre developmental disorder of this latter process. Persons with this syndrome develop a belief early on that part of their body doesn't belong to them, and they become desperate to get rid of it. They don't accept a limb as being part of them, even though it functions perfectly. This leads to an overwhelming
desire for amputation. Only when their arm or leg has been amputated—and around 27 percent of these individuals succeed in achieving this—do they feel “complete.” Surgeons who comply with these wishes run the risk of being fired for removing a healthy limb. That's curious, because the principle being applied is similar to that used in the case of transsexuals and even circumcision. (Moreover, the latter operation is carried out on baby boys who are incapable of giving informed consent, and it can lead to complications like bleeding, infection, a perforated urethra, narrowing of the urethra, scarring, and malformation.) However, acceptance of the problems of BIID sufferers doesn't seem to be coming any time soon. Psychotherapy or pills don't on the whole change the sufferers' way of thinking. There's a sole recorded case of a BIID patient whose misery was alleviated by antidepressants and cognitive behavioral therapy, but he later declared that, although it was nice to talk to someone, the therapy had done nothing to resolve his BIID issue.