We Are Our Brains (24 page)

FIGURE 21.
The brain seen from below. Breathing, heart rate, temperature, and sleep-wake cycles are regulated in the brain stem (1). The olfactory (smell) system consists of the olfactory bulb (2), the olfactory nerve (3), and the uncus, part of the temporal lobe (4). Also shown are the optic chiasm (5), where the optic nerves partially cross, the mammillary bodies (6), and, in between, the pituitary gland (7).

In the Netherlands, life in a persistent vegetative state isn't regarded as a dignified existence. Keeping patients alive in such situations is deemed medically futile and, in consultation with the family, the decision is usually made to stop treatment. Since the treatment being withheld is medically futile, these aren't, formally speaking, cases of euthanasia. Yet in the Netherlands, too, there are people who are in a coma for long periods of time. It's scandalous that Internet sites exploit the desperation felt by the families of such patients. The organization CWUBS (Coma Wake Up Brain Stimulations), for instance, offers therapy costing over €10,000 to awaken people from a persistent vegetative state. But even giving €100,000 worth of therapy to patients whose cerebral cortex is irreparably damaged won't bring them out of a coma; the sole beneficiary of such therapy is CWUBS itself.

Locked-In Syndrome

The reverse of a vegetative state is locked-in syndrome, which occurs when the brain and the spinal cord are completely separated due to damage low down in the brain stem that prevents nerve fibers from controlling muscles. In such cases the brain is otherwise entirely intact, and the patient is fully alert. However, they are completely paralyzed, so they can't communicate their alertness to their surroundings. They can see, hear, and understand everything, but they can't move or speak. They can only close their eyelids and move their eyes.

In 1995, the French journalist Jean-Dominique Bauby suffered a stroke after which he lay in a coma for twenty days. When he awoke he was totally paralyzed, able to control only his left eyelid. A means of communication was devised whereby the alphabet was read aloud and he blinked when the reader got to the right letter. In that way, letter by letter, he was able to write a memoir,
The Diving Bell and the Butterfly
, describing his full awareness of his surroundings,
himself, and the appalling situation in which he was trapped. An impressive film with the same title was made in 2007. In it, extracts are also read from
The Count of Monte Cristo
(1844), by Alexandre Dumas, describing a character with locked-in syndrome, M. Noirtier de Villeforte, who ends up paralyzed and mute after suffering a stroke but is able, by moving his eyes and eyelids, to avert a poisoning and an undesirable marriage. A more recent instance is that of Nick Chisholm, a New Zealander who was knocked out during a game of rugby in 2000. At first he appeared to be simply concussed, but he later had a series of epileptic fits and brain stem infarcts. He was thought to be in a coma until his mother and girlfriend managed to convince doctors that he was aware of what was going on around him. He has since made a partial recovery. In the case of locked-in syndrome, families tend to be aware of consciousness before the doctors, but in the case of a coma families are more likely than doctors to be mistaken in thinking that consciousness exists.

Brain Death

Before the era of transplantation, diagnosing a patient as dead was simple: In the doctor's opinion, a patient's heartbeat and breathing had ceased and couldn't start again. As a doctor, there were always a few minutes of doubt, but then the irreversibility of the process would become clear. Every now and then, a skier is dug out from an avalanche, no longer breathing and with no discernible heartbeat, but subsequently recovers. Cases in which someone is apparently dead but then revives are scarce enough to be well-known. King Louis IX is said to have moved in his coffin during a requiem mass being held for him. The funeral was halted and the king recovered, afterward going on a crusade to Egypt, where he repaid the debt he owed to death. In French, the term for undertaker is
croque-mort
(someone who bites the dead), alluding to the medieval custom of
biting a corpse's big toe in order to make sure that the person really was dead. A few years ago, a doctor in the Netherlands mistakenly pronounced an eighty-three-year-old woman dead. When the undertaker's men came to pick up her body from the bathroom floor, it suddenly emitted a quiet “ouch.” The old lady suffered no ill effects. (The same can't be said of the doctor.)

From the moment that patients with severe brain damage could be hooked up to breathing apparatuses, the classic diagnosis of death became obsolete, because heart rate and breathing were artificially sustained while a patient was unconscious or “brain-dead.” This state can persist interminably. The former Israeli prime minister Ariel Sharon has been on a ventilator since suffering a severe stroke in 2006. His sons want his treatment to continue. In situations like this, the diagnosis is “brain-dead” rather than “dead.”

The original definition for the diagnosis “brain-dead” was the “irreversible end of
all
brain activity.” But the brains of a quarter of brain-dead patients go on producing the antidiuretic hormone ADH (vasopressin), which ensures that the kidneys reabsorb many liters of water a day from urine (see
chapter 5
). You can instantly tell when the brain cells that make ADH are dead because the patient produces between ten and fifteen liters of watery urine each day. In brain-dead individuals whose ADH-producing brain cells are still intact, their urine bag fills with a mere one and a half liters of properly concentrated urine.

Various other groups of brain cells may remain active in brain-dead patients, but they won't contribute to the recovery of consciousness. The term
brain-dead
was later redefined by a committee at Harvard Medical School (HMS) as entailing irreversibly fixed pupils, the absence of brain stem reflexes, and the permanent absence of “higher brain functions” like cognition and consciousness. The latter is actually a logical reversal of Descartes's famous “Cogito, ergo sum” (I think, therefore I am). If you can no longer think, because your brain no longer functions, you have also ceased to exist as a person.

Transplantation

Determining brain death is also important for organ transplantation. Besides ascertaining that the HMS criteria apply, the Dutch Health Council also recommends establishing that there's no longer any electrical activity or blood circulation in the brain. Finally, the ventilator is temporarily switched off to check that there's no question of spontaneous breathing. This provides an extra guarantee that the potential organ donor is indeed brain-dead. If these conditions are met and the person in question has previously given permission for their organs to be used, they can be transplanted. Since under the circumstances a person is no longer conscious of their own body, we of course shouldn't interpret the reflex reactions of the spinal cord that occur when a surgeon removes organs from a brain-dead patient as an expression of pain. That's easily said, but it's quite a different thing for the surgeon who sees the body respond when he makes an incision to remove its organs. In the United Kingdom, anesthesia is administered for this procedure. The Dutch association of anesthetists finds this nonsensical, and scientifically speaking they're right. In such cases an anesthetic is given to preserve not brain-dead patients but rather transplant surgeons from discomfort.

There are two aspects to consciousness. First and foremost, we are
conscious of our surroundings.
A rudimentary form of consciousness is found in every living organism. Even single-celled organisms creep toward food and away from poisonous substances and are thus aware of their surroundings. But it's unlikely that they are conscious in the way that we are. For that, you have to go quite a way up the evolutionary
ladder. The second aspect of consciousness is that we are
conscious of ourselves.
Self-awareness is certainly not unique to humans and has been demonstrated in young children and animals using experiments with mirrors. Various species prove to have a highly developed sense of self-consciousness, providing the basis for complex social relationships. Some chimpanzees, orangutans, and possibly also gorillas can recognize themselves in mirrors. A dolphin can see ink marks on its body in a mirror, and an ape can wipe a spot of paint off its own face when it sees it in a mirror, just as a child starts to recognize itself in a mirror between the ages of one and two. An Asian elephant can also recognize itself in an enormous mirror, inspect its own ear, and discover that its face has been marked, as Frans de Waal has shown. And self-consciousness isn't exclusive to mammals. Magpies can also recognize their reflected image. This was shown by placing stickers on their bodies in a place that they could see only in a mirror. The birds removed the stickers from their bodies without touching the mirrors, showing that they recognized their own image.

Some brain structures are crucial for consciousness, such as the cerebral cortex and the thalamus, along with a functional link between the two areas (
fig. 20
). An individual whose brain stem functions are still intact (meaning that they can breathe and regulate their blood pressure and body temperature independently) but whose cerebral cortex or the connections to it have been destroyed can no longer be said to possess consciousness. This situation applies to patients in a vegetative coma. They don't need to be hooked up to a ventilator, and their heart rate is normal. They can open and close their eyes and groan as well as cry and sometimes laugh uncontrollably. Their sleep-wake rhythm is still maintained by the brain stem (
fig. 21
), so they sometimes appear to “wake up,” but without showing any consciousness of their surroundings or themselves.

While the cerebral cortex is essential to consciousness, its functioning isn't in itself sufficient for consciousness. Under anesthesia, for example, light stimuli still arrive in the visual cortex with a delay of one hundred milliseconds, but we aren't conscious of them. Studies
have also shown that even when fully sedated, patients can be influenced by verbal suggestions, music, or the sound of the sea, despite their unconscious state. For consciousness to be intact, the area of the cerebral cortex where the stimulus arrives must also be able to communicate actively with other areas of the brain, which is impossible under anesthesia.

For normal consciousness, you also need an intact thalamus (
figs. 2
and
19
). The thalamus lies in the center of the brain and plays a crucial role in consciousness, because it's there that all sensory information (except smell; see
fig. 21
) is received and rerouted to the cerebral cortex. Damage to the thalamus disrupts consciousness. Conversely, a case is known of someone having been restored to consciousness through electric stimulation of the thalamus. Following an accident, a thirty-eight-year-old man spent around six years in a minimally conscious state, between coma and consciousness. He could occasionally communicate through eye or finger movements, but never through speech. Stimulation electrodes were implanted on both sides of his thalamus; within forty-eight hours of stimulation commencing, he woke up. Over the six months of stimulation that ensued, his attention improved, as did his response to assignments, his control of his limbs, and his speech. From a scientific point of view this is an intriguing experiment, but it's debatable whether he will be able to lead a dignified existence in the wake of this heroic remedy. It created an ethical dilemma, in that stimulation of the thalamus made him aware not only of his surroundings but also of himself and his terrible predicament.

Some areas of the brain, like the cerebral cortex and thalamus, are crucial for full consciousness (
figs. 19
and
20
). For consciousness to arise, not only must these areas and their links be intact, but they must also be able to communicate well with each other. Functional scans (fMRI) of patients in a vegetative coma show that parts of the cerebral cortex still function. A strong pain stimulus can even activate the brain stem, thalamus, and primary sensory cortex (
fig. 22
) of such patients. But these areas have been shown to be functionally disconnected from higher-order areas of the cortex that are necessary to consciously register pain. In the same way, a sound stimulus can activate the primary auditory cortex, but the functional disconnection means that such signals don't reach the higher-order areas necessary to register sound consciously. In other words, neuronal activity in the primary sensory or auditory cortex is necessary but not sufficient for consciousness. For consciousness, a functional connection is needed with the network of the prefrontal and lateral cortex (frontoparietal network). So recovery from a vegetative state goes hand in hand with recovery of the functional links between this network's components.