We Are Our Brains (4 page)

One could also think of more peaceful metaphors, like the air traffic control center of a large airport. But if you look back at all the metaphors of previous centuries, you realize that you're simply comparing the most recent technology devised by our brains to the brain itself. Indeed, there appears to be nothing more complex than that fantastic machine.

FIGURE 2.
Cross section of the brain. (1) The cerebrum, with the convoluted cerebral cortex. (2) The corpus callosum, a bundle of neural fibers connecting the left and right sides of the brain. (3) The pineal gland, which at night secretes the sleep hormone melatonin, a substance that also inhibits puberty in young children. (4) The fornix, which transports memory information from the hippocampus to the mammillary bodies at the base of the hypothalamus (
fig. 25
), after which it travels on to the thalamus (5) and cortex (1). (5) The thalamus, where sensory information and memory information are sent. (6) The hypothalamus, which is crucial to the survival of the individual and the species. (7) The optic chiasma, where the optic nerves cross. (8) The pituitary gland. (9) The cerebellum. (10) The brain stem. (11) The spinal cord.

Somebody once suggested that I went in for brain research because my father was a gynecologist, the theory being that I chose the organ that lay as far as possible from his field of work. This psychoanalytical explanation fails to take account of the research I've done in the function of the brains of both mother and child during childbirth, working with gynecologists like Kees Boer at Amsterdam's Academic Medical Center. The conclusion of Boer's PhD thesis was that smooth childbirth requires good interaction between the brains of mother and child.

Both brains play a role in speeding up labor by secreting a hormone,
oxytocin, into the bloodstream that makes the uterus contract. The mother's biological clock imposes a day-night rhythm on the birth process, which explains why most children are born during the quiet phase, at night and in the early hours of the morning. That's also the time when birth progresses fastest and requires the least assistance.

Labor starts when the baby's blood sugar level starts to drop—a sign that the mother can no longer provide the growing child with sufficient nourishment. Michel Hofman has calculated that labor is triggered at a stage when the child accounts for around 15 percent of the mother's metabolism. That point is reached earlier by twins, triplets, and so on, which is why they are born prematurely. While still in the womb, the brain cells in the child's hypothalamus respond to a drop in blood sugar level in the same way that they later respond to a lack of food in adulthood, by stimulating the stress axis. This induces a series of hormonal changes, making the uterus contract (
fig. 3
). The contractions, stimulated by oxytocin, make the baby's head press against the cervix. This in turn triggers a reflex, via the mother's spinal cord, which causes the release of yet more oxytocin. The baby's head then exerts more pressure, triggering the same reflex. The child can only escape from this chain reaction by being born.

Various psychiatric disorders are associated with a difficult birth. It has long been known that a high percentage of patients with schizophrenia experienced problems at birth, such as delivery by forceps or vacuum pump, low birth weight, premature birth, premature breaking of the waters, or time spent in an incubator. It was once thought that difficult births caused brain damage, leading to schizophrenia. We now know that schizophrenia is an early developmental brain disorder largely caused by genetic factors (see
chapter 10
). So a difficult birth can be seen as a failure of interaction between the brains of mother and child and thus as the first symptom of schizophrenia, even though the disease doesn't develop fully until puberty. The same applies to autism, another early developmental brain disorder (see
chapter 9
) that also often goes hand in hand with birth-related
problems. Recent studies have shown that girls who suffer from the eating disorders anorexia and bulimia nervosa often had problems at birth, including low birth weight. The more numerous such problems are, the earlier eating disorders manifest themselves in young adults. One wonders whether their hypothalami started out unable to deal well with glucose levels, given that a decrease in them signals the start of labor. So here, too, birth-related problems of this type could be seen as the first symptoms of a malfunction of the hypothalamus, later taking the form of an eating disorder.

FIGURE 3.
When the growing fetus registers that the mother can no longer provide sufficient nourishment, the stress axis in its hypothalamus is activated. Its adrenal gland is stimulated by ACTH to produce cortisol. This reduces the effect of progesterone from the placenta and causes estrogen production to increase. As a result, the uterus becomes more sensitive to oxytocin, activating labor pains and starting the birth process.

A child with a developmental brain disorder can't fulfill its essential role during labor. Extremely delicate interaction is needed between mother and baby for birth to proceed well. Thinking about birth in this way takes a bit of getting used to because it means that a child's say in life starts right from birth.

In one-third of cases, brain disorders that manifest themselves as a child develops are wrongly ascribed to a difficult birth. In fact, the brain defects that cause such conditions as learning disabilities and spasticity often come into being long before birth.

The English surgeon William John Little is credited as the first person to identify spastic diplegia (a form of cerebral palsy), having described the condition in forty-seven children in 1862. His conviction that it was caused by birth trauma is still held by many to this day. Strangely enough, little attention has been paid to the opposing view held by Sigmund Freud, who, after a careful study in 1897, concluded that a difficult birth couldn't cause spasticity but that both the neurological condition and the difficult birth should be seen as the consequence of a developmental disorder of the fetal brain. Problems at birth are often also blamed in the case of children with learning disabilities. Prader-Willi syndrome is a genetic disorder that
causes morbid obesity over the course of time (see
chapter 5
). Many children with this syndrome have a difficult birth and go on to have learning disabilities. These aren't caused by birth-related problems but by the genetic abnormality that was present from conception.

In only 6 percent of children born at due date with spasticity and a mere 1 percent of children with learning disabilities can the disorder be attributed to a lack of oxygen at birth. The vast majority of children with these conditions experience problems long before birth, as is evident from their slow growth and lack of movement in the womb. Spasticity has many different causes, ranging from genetic abnormalities and intrauterine infections to exposure to chemicals, iodine deficiency, and long-term oxygen deficiency in the womb. Conversely, it's striking that serious brain damage often does not result when a normal fetus is suddenly deprived of oxygen at birth, as Freud already noted. To understand why he was right, you need to be aware of the active role played by the fetus in the birth process. Its brain plays a crucial part, both in initiating labor and during its course. The relationship between a difficult labor and impaired brain function is usually the opposite of what is generally assumed. A difficult labor or premature or delayed labor tends to be the
consequence
of a problem in fetal brain development. And that deficiency can in turn be caused by genetic factors, lack of oxygen in the womb, infections, or exposure to medication or addictive substances ingested by the mother, like morphine, cocaine, or nicotine. So efforts to establish the cause of premature or difficult birth are incomplete without examining the child's brain.

That a child's brain plays a very active role in labor is something we established thirty-five years ago, in a study with the gynecologist W. J. Honnebier. We looked at the births of 150 anencephalic infants (children born with most of their brain missing,
fig. 4
). Babies with this condition are usually born extremely prematurely or very overdue, and labor proceeds much more slowly than normal. That birth takes twice as long (and the birth of the placenta three times as long) is due to the absence of oxytocin in the child's brain. Half of these babies
don't survive, which shows how important a well-functioning fetal brain is to the process of labor. Another hormone secreted by the fetal brain, vasopressin, ensures that blood is mainly directed to those organs that are crucial to survival during birth, like the heart, the adrenal gland, the pituitary gland, and the brain. This involves depriving less vital areas like the intestines. Animal studies have revealed the many complex chemical steps that are necessary for the birth process. But it all starts when a child's brain registers that the maternal food supply is becoming inadequate, causing it to give the signal for the onset of labor, just as the Greek doctor and philosopher Hippocrates noted over two thousand years ago.