Welcome to Your Brain (36 page)

theory-of-mind inference. (
Chris thinks I can’t walk down stairs.
) In religious belief, the level of

reasoning is more complex. Multiple steps of inference are needed to follow the mutual motivations

of multiple entities. A core necessity in religion is to make, at a minimum, a two-step inference:
God

thinks
(step 1)
that I should worship him
(step 2). The details of most religions involve more steps

of inference. To take Christianity as an example, having to keep straight what one wants alongside the

desires of God, Jesus, the Holy Spirit, the teachings of the church, and one’s fellow churchgoers gets

very complicated.

Most apes and monkeys seem unlikely to be capable of multistep inferences about mental states, a

minimum condition for religion. But observations of big-brained apes such as chimpanzees suggest

that they can achieve at least Osa’s level of inference. For instance, a subordinate chimp will prefer

to go after a piece of fruit that cannot be seen by a dominant chimp over one that is visible to the

dominant chimp. Similarly, if you appear unwilling to give a grape to a chimp, it will lose interest. If

you show the same chimp that you’re willing but unable to give it the grape, it will wait longer.

Chimpanzees make these inferences with a brain that is less than one-third the weight of ours. The

jury is out on whether chimpanzees can form religious beliefs. In one behavior that is very suggestive,

during thunderstorms some chimps sway around with their hair standing on end, an act that some

people have interpreted as resembling a dance. Are they superstitious? Or just afraid? At this point,

since the evidence for chimpanzees having a theory of mind at all is so recent, we can only wait for

more information.

Did you know? The neuroscience of visions

Mountains are important in the three major monotheistic religions practiced today:

Judaism, Christianity, and Islam. All three involve special visions that occurred at great

heights. Moses encountered a voice emanating from a burning bush on Mount Sinai. Jesus’s

followers witnessed the Transfiguration on what was probably Mount Hermon, and

Muhammad was visited by an angel on Mount Hira (Jabal an-Nour). These visions are but

three examples of a broader category of mystical experience. Yet another prominent

example is the appearance of the Virgin Mary to Juan Diego as he ran across Tepeyac Hill

in Guadalupe, Mexico. Commonly reported spiritual experiences include feeling and

hearing a presence, seeing a figure, seeing lights (sometimes emanating from a person), and

being afraid. Curiously, very similar phenomena are reported by a group generally not

thought to be very mystical: mountain climbers. Could it be something about the mountains?

Mountaineers have long known to watch for the dangers of thin air. Acute mountain

sickness occurs above altitudes of twenty-five hundred meters (about eight thousand feet).

Many of the effects are attributable to the reduced supply of oxygen to the brain. Reaction

times are measurably reduced at altitudes as low as fifteen hundred meters (about five

thousand feet). At twenty-five hundred meters or higher, some mountaineers report

perceiving unseen companions, seeing light emanating from themselves or others, seeing a

second body like their own, and suddenly feeling emotions like fear.

Oxygen deprivation is likely to interfere with activity in neural structures in and near

the temporal and parietal lobes of the cortex. These brain regions are active in visual and

face processing, and in emotional events. An extreme case of disturbed function is an

epileptic seizure. Temporal lobe seizures often result in intense religious experiences,

including feeling the presence of God, feeling that one is in heaven, and seeing emanations

of light. Temporal lobe seizures are triggered more easily under conditions that elevate

endorphins, such as high stress. The exertion of climbing a mountain would certainly be a

source of stress, and religious visions often occur under stressful conditions. Indeed, as a

general rule, visions are associated not only with mountains but with other remote areas

where environmental conditions are extreme, such as deserts. Seizures are thought to have

caused religious visions in Saint Teresa of Ávila and Saint Thérèse of Lisieux, and may

have triggered conversions of previously nonreligious people, including the apostle Paul on

his way to Damascus and Joseph Smith, the founder of the Church of Latter-day Saints.

A final element in religion is the passing on of teachings and traditions. Such continuity requires

language, which permits accumulated ideas to be modified, allowing doctrine and dogma to be

communicated from generation to generation. For now, humans seem to be alone in having the basic

mental tools—a theory of mind and language—to generate organized religion. But we may not have

always been the only ones with this gift. Before our species made the leap to religious belief some

tens of thousands of years ago, with our ritual burials and cave art symbolism, Neanderthals, another

branch of the
Homo
lineage, may have done so as long as one hundred thousand years ago.

Our capacity for language allows our search for causes and effects to take on a new dimension in

the form of narrative. Human beings are storytelling, narrating animals, and as such have developed

complex explanations for a wide variety of daily experiences and problems of existence. In his book

Moral, Believing Animals
, sociologist Christian Smith discusses human belief systems as a general

phenomenon in which the world is placed in a coherent conceptual framework, a story that gives

meaning to daily experience.

The search for explanation in different contexts is a central feature of many belief systems.

Examples of explanatory narratives include an understanding of historical events (political science),

natural phenomena (science), and social dynamics (psychology and sociology). In this way, religion

is an example of yet another narrative, one that looks for meaning in the experience of living—

spirituality. Although all these forms of narrative use different rules and have very different goals, any

eventual neuroscientific explanation of how we form narratives is likely to address them in similar

ways.

Once explanatory ideas take root, the sky’s the limit on what a conceptual structure can explain or

recommend. Why should we not harm our neighbors? Where did Grandma go when she died? Who

made the world? When we encounter unbelievers, should we attempt to kill them or convert them?

Of course, asking or answering these questions does not require belief in a god. In one episode of

the animated television show
South Park
, Cartman travels to a hypothetical future in which three

factions are engaged in a bitter battle for world dominance. They share in common a venerated

founder and much doctrine, but a small difference has led them to fight to the death. Their doctrine?

Atheism. Their founder? None other than Richard Dawkins. Speaking as neuroscientists, we find the

most unrealistic aspect of this show to be not the warring factions of atheists, but the fact that one of

the factions is composed of … sea otters. Real otters aren’t likely to be able to keep track of enough

actors to form a dogmatic belief system. Anyway, we hope not.

Chapter 29

Forgetting Birthdays: Stroke

On a winter morning in 2002, Sam phones his mother in California. Today is his brother Ed’s

birthday, and his Chinese-born parents are not sentimental about birthdays. Besides, it gives him a

reason to call her, which she tells him doesn’t happen enough.

“Today is Edward’s birthday,” he tells her. “Oh, really?” she replies. “What’s the date today?” A

red light in Sam’s mind starts blinking, and his mother also becomes anxious. She knows that she is

supposed to know her son’s birthday. Fighting his own rising panic, Sam starts asking her other

questions. “When is my birthday?” She can’t remember. “Mom, when is your birthday?” She draws a

blank. What about the message she left last week about going to Europe together? Nothing.

By this time, she has also realized that something is seriously wrong. She starts writing down the

answers to all these questions, writing down everything. His father comes on the line. He’s not

exactly sure how long she has been like this, but he becomes convinced that she needs to get to the

hospital. At age sixty-six, Sam’s mother has had a stroke.

A stroke is an event in which blood flow to a brain region is disrupted, either when a blood

vessel breaks (a bleeding, or hemorrhagic, stroke) or because it becomes blocked (a clotting, or

thromboembolic, stroke). The great majority of strokes start from a thrombus, a clot that forms in a

blood vessel that is hardened by arteriosclerosis or otherwise damaged. The thrombus can form in the

brain itself or travel from elsewhere and get stuck in the brain, in which case it is called an

embolism. In all strokes, a part of the brain is deprived of oxygen and glucose, which delivers energy

throughout the body, and waste products can no longer be carried off. These events resemble what

happens during a heart attack, when the flow of blood to the heart is stopped. For this reason, a stroke

is sometimes called a “brain attack.”

Strokes can happen to younger adults but are more common among older people. In the U.S.,

people age fifty-five and older have a one-in-five chance of having a stroke during their lifetimes.

Among men, the risk is slightly lower, but is still one in six. Last year, about seven hundred thousand

people in the U.S. had strokes of some kind. Nearly five million survivors of stroke are alive today.

Pound for pound, your brain uses more energy than any other organ of your body. All of this

energy is carried to your brain by the blood. If the blood flow stops for any reason, it can stop the

functioning of neurons almost instantly. Different parts of your brain take on different tasks. For this

reason, the symptoms of stroke are specific to the area of the brain that has stopped functioning.

The most common places for a stroke are the cerebral hemispheres, because they are the largest

part of your brain—about four-fifths of the total volume. The most common symptoms of stroke are

loss of the ability to move a limb or loss of sensation in a part of the body. The cortex is also

required for thinking, and so another common symptom is confusion. Yet another symptom is a sudden

inability to speak or comprehend language.

The symptoms of stroke can also occur in other cases, known as transient ischemic attacks, but the

strokelike symptoms of these episodes reverse in minutes. These events are not well understood, but

they are probably caused by a loss of blood flow. Maybe a small clot forms, slowing blood flow by

just a little, then dissolves.

In stroke, the initial symptoms persist. If the blood flow is stopped for more than a few minutes,

neurons begin to die. Over the next hours, up to a day, damage gets progressively worse. By the end,

many neurons have died. In one estimate, each minute of blocked blood flow destroys 1.9 million

neurons, 14 billion synapses, and 12 kilometers (7.5 miles) of myelinated axons.

Can the effects of stroke be reversed? Currently, the answer is yes, but only in the first three

hours. During this short window, if the victim is taken to an emergency room and diagnosed, it may be

possible to give drugs that reopen clogged vessels or treat bleeding. After that, neurons are on their

way to dying, and it’s mostly too late to help. However, only a small fraction of stroke victims ever

receive this treatment, the ones who are taken to the right emergency room, usually at large urban

hospitals.

Four days later, Sam is with his parents in their doctor’s office. By now, irreversible damage has

been done, but he doesn’t know this yet. He has heard about new stroke treatments, and he is hoping

that something can be done. His parents came to the U.S. in the 1960s, and they have an attitude

toward doctors that is common among older immigrants—they go back and forth between being

intimidated and trusting everything the doctor says. Sam figures he’d better be there.

His parents’ family doctor, who works at the local community health center, is a nice old fellow,