Welcome to Your Brain (13 page)

As in other sensory systems, areas of the brain that analyze touch information are organized into

maps, in this case, maps of the body surface. The size of a given brain area depends on the number of

receptors in each part of the body, rather than on the size of that body part, so that the part of the

brain’s map that receives information from the face is larger than the area that receives information

from the entire chest and legs. Along the same lines, in a cat’s brain, a large area is occupied by

neurons that respond to the whiskers.

Responses to painful stimuli are carried by separate receptors and analyzed by brain areas

distinct from those that carry information about regular touch. One family of pain receptors detects

heat and cold, while another family of receptors detects painful touch.

Practical tip: Does acupuncture work?

Having needles stuck into your skin doesn’t sound like much fun, but a lot of people

swear by it. The therapeutic use of needles, called acupuncture, is routine in Asia and has

become increasingly common in the West over the past three decades. Roughly 3 percent of

the U.S. population and 21 percent of the French population have tried it. About 25 percent

of medical doctors in the U.S. and U.K. endorse acupuncture for some conditions.

The scientific evidence for medical benefits from acupuncture is mixed and very

controversial. Many of the studies are done and evaluated by people with a vested interest

in proving or disproving its effectiveness—making it difficult to know who you should

listen to. In our reading of the scientific literature, the best evidence suggests that

acupuncture is more effective than no treatment at all for some conditions, notably chronic

pain and nausea. For most people, acupuncture seems to be about as effective as

conventional treatments for these conditions, but there is little or no evidence that it’s

effective for other conditions, such as headache or drug addiction.

Traditional practitioners believe that acupuncture improves the flow of
qi
—a Chinese

word that, roughly, means
energy
—circulating in pathways of the body. To unblock the

energy flow, needles are inserted along these pathways, though different authors disagree

on the exact locations, number of pathways, and acupuncture points. Attempts to identify

these pathways in terms of the body’s electrical or other physical properties have not been

successful.

However, acupuncture definitely has some effect on the brain. Functional imaging of

brain activity shows that acupuncture has specific effects on particular brain areas. For

instance, an acupuncture point in the foot traditionally related to vision has been reported to

activate the brain’s visual cortex, while stimulation at other sites nearby do not. However,

a follow-up study reported a different result, creating considerable uncertainty about this

conclusion. Brain areas that control pain are activated by acupuncture—but also by the

expectation of pain relief or by sham acupuncture at incorrect sites.

This brings up a major problem with evaluating any medical treatment (and especially

acupuncture): a lot of patients feel better just because someone is paying attention to their

problem. This is the reason that more than half of the patients in many studies report

improvements in their conditions after taking sugar pills. Scientists solve this problem by

doing double-blind studies, in which neither the patients nor the health care providers know

who’s receiving the real treatment and who’s getting the fake one.

Of course, it’s tough to keep patients guessing about whether needles are being stuck in

them or not. Some researchers have used sham acupuncture, inserting needles into incorrect

locations. Sham acupuncture is often found to be as effective as real acupuncture, but it’s

easy to believe that sham acupuncture might have some therapeutic effect in its own right. A

few studies have used a telescoping probe that retracts as it approaches the skin, feeling

like a needle to people who haven’t experienced real acupuncture. This solves half the

problem, but the practitioners still know whether they are giving real or fake treatments,

which may lead them to behave differently with patients in the two groups and therefore

influence their responses. Telescoping-probe studies have given mixed results. Most of

them show real and sham acupuncture to be equally effective, but a large minority find real

acupuncture to be more effective.

At the end of the day, you probably don’t care why you’re feeling better, as long as you

are, and there’s no reason not to try acupuncture if you’re interested. In the hands of a

qualified practitioner, it’s pretty safe, causing serious problems for fewer than one in two

thousand patients. Even if many of the details of the process turn out to be folklore, as we

expect that they will, acupuncture does seem to have practical value in treating certain

conditions.

Prediction is hard, especially of the future.

—Unknown

If you’ve ever touched a hot stove, you know that many pain receptors can activate reflex

pathways that allow you to make a very rapid response to sensations that indicate the possibility of

immediate danger to your body. However, these reflexes—and all responses to pain—are very

strongly influenced by the person’s interpretation of the painful situation. Indeed, there is an entire set

of brain areas that influences activity in the direct pain-sensing parts of the brain based on context and

expectation. This effect can be as powerful as a near-complete lack of pain in a soldier with a serious

injury on the battlefield. More commonly, we’ve all seen the opposite effect—the sudden

intensification of pain in a small child when his mother approaches.

These responses are often called psychological, but that doesn’t mean they’re not real: people’s

expectations and beliefs create physical changes in the brain. If people are given a pill or an injection

that contains no active drug but are told that it will relieve their pain, activity increases in the parts of

the brain that are normally involved in modulating pain. When people are told that a cream will

reduce the pain of an upcoming electric shock or heat stimulus, they not only show increased activity

in pain-controlling regions, they also show reduced activity in parts of the brain that receive pain

signals. In addition, pain relief from such placebo treatments can be blocked by naloxone, a drug that

prevents morphine from acting on its receptors. From these results, we can conclude that when

patients are told that their pain will be reduced, the brain responds by releasing natural chemicals that

reduce pain, which are called endorphins. Even a saltwater injection, the most innocuous treatment

possible, can lead to pain relief—and also the release of endorphins.

Practical tip: Referred pain

Have you ever had pain caused by indigestion that made it feel like your chest was

hurting? This sort of confusion happens because all the nerves that sense pain in the internal

organs send signals through the same pathways in the spinal cord that carry information

from the body surface. This convergence leaves the brain uncertain about what’s wrong.

Pain felt in a place other than its true source is called referred pain.

For this reason, doctors learn that when patients complain about pain in their left arm, it

may indicate a heart attack. Similarly, pain from a kidney stone may feel like a

stomachache, gallbladder pain may be felt near the collarbone, and pain from appendicitis

may hurt near your bellybutton. If you have persistent pain without an apparent cause in any

of these areas (but especially the left arm), you should see a doctor as soon as possible.

Endorphins act on the same receptors that respond to morphine and heroin. The existence of

endorphins is the reason that your body has receptors that respond to these drugs. Endorphins may

allow pain relief when the brain decides that it’s more important for the body to be able to go on

(perhaps to escape from continuing danger) than it is to protect the injury from further damage.

Scientists at Stanford have been trying to use brain imaging to train people to activate pain-

controlling areas of their own brains. If it works, this technique could allow people with chronic pain

to reduce their own discomfort without needing fake pills or creams or injections. The scientists use

functional imaging to detect activity in the target region of the brain. Subjects can see on a computer

display whether they are achieving the desired effect. Using this technique, people have been able to

gain voluntary control over the activity in one area of their brains—though it remains to be seen

whether this approach will lead to pain relief in patients.

Part Three

How Your Brain Changes Throughout Life

Growing Great Brains: Early Childhood

Growing Up: Sensitive Periods and Language

Rebels and Their Causes: Childhood and Adolescence

An Educational Tour: Learning

Reaching the Top of the Mountain: Aging

Is the Brain Still Evolving?

Chapter 10

Growing Great Brains: Early Childhood

When we were kids, our parents tried to keep us safe and stop us from running with scissors. As

far as we can remember, that was enough to keep their hands full. Today, middle-class family life has

become a far more complicated affair. Daily activities are a blur of flash cards and baby aerobics.

Magazines say that you can increase your children’s intelligence by playing Mozart for them when

they’re young—or even before they’re born. Parents worry that if little Emma doesn’t attend the right

preschool, she’ll never get into a decent college. Every few years, another expert piles on more

anxiety by explaining how a child’s experiences in early life determine intelligence and success later

on.

Our own parents had very different philosophies of child rearing. Sam spent hours each day

watching television and can still recite the plot of almost every episode of
Star Trek
and
The Brady

Bunch
. Sandra was five years old before friends at school let her in on the secret that there were

other channels on TV besides PBS. Since her parents never watched anything else, she spent her early

years with
Sesame Street
and other carefully designed educational fare. Yet Sam seems to have made

up for any possible brain damage, and, indeed, as a university professor, is now even responsible for

the training of younger minds.

It’s true that the early environment influences how a child’s brain grows, but you rarely need to

worry that your child isn’t getting enough stimulation. There’s no question that childhood deprivation

can interfere with brain development. To start with an extreme example, children who spent their

early years in Romanian orphanages often have lifelong problems. But these poor kids were left alone

in a crib for years, visited only by a caretaker who came along every so often to change diapers.

Unless you’re locking your kid in a closet (in which case, you should stop doing that right away), you

don’t have to worry about how this sort of serious deprivation affects brain development.

Myth: Listening to Mozart makes babies smarter

One of the most persistent brain myths is that playing classical music to babies

increases their intelligence. There’s no scientific evidence for this idea, but it’s proven

amazingly persistent, probably because it allows parents to address their anxiety about their

children’s intellectual development—and because sellers of classical music for children

encourage the belief every chance they get.

This myth began with a 1993 report in the scientific journal
Nature
that listening to a

Mozart sonata improved the performance of college students on a complex spatial

reasoning task. The researchers summarized the effect as equivalent to an eight- to nine-

point gain on the Stanford-Binet IQ scale. Journalists didn’t find this result immediately

fascinating; they reported it about as much as any other science story published in the same

journal that year.

The idea really took off after the 1997 publication of
The Mozart Effect
by Don